Sunday, September 17, 2017

 

Issue #548: Astro-Video, Slight Return


I’m not talking about new-fangled video observing, “electronically assisted astronomy” as the denizens of a certain contentious forum on a famous (in a small amateur astronomy sort of way) website call it. I’m not talking about using digital CCD/CMOS cameras with short exposures to simulate video observing. I am talking about real-deal video observing with analog video cams.

That doesn’t mean I don’t like the new style digital astro-video cameras. I’ve reviewed a couple of them for Sky & Telescope Test Reports and was impressed. Their strength is that they are far more able to deliver pretty, smooth-looking images than the analog cams were. And those images sure are easier to get into a computer for manipulation than analog video was. You no longer need one of those blasted frame-grabbers; just plug a USB cable into the camera and laptop and you are ready to go. It ain’t all gravy, though. Analog cameras like the Mallincam Xtreme are still more sensitive than almost anything else.

Those were some of my thoughts as I pulled my Xtreme from her dusty case and mounted her on a telescope for the first time in nearly three years. I was in a hurry to get some images for a magazine article, and was pretty sure video would be the quickest way to do that. Which is just one of old-fashioned style video’s pluses. But why, then, had my Xtreme sat unused for so long? Maybe because I'd rarely observed with anything but video when I was doing the The Herschel Project.

The Herschel Project, which I began in earnest in 2009, was my quest to view all 2500 of the deep sky objects recorded by William and Caroline Herschel. It was the biggest observing campaign of my life, and finishing it in about three years as I planned meant night after night of pedal-to-the-metal observing, much of it with video, was required.

While I could have done all, or nearly all, of the H objects visually with my larger scopes, that would only be true given excellent dark skies. At my club site, I needed video to reliably bring home all the small and dim galaxies that infest the list. That’s why I started using video for the Project, anyhow. Frankly, I became so fond of observing the Herschels with my Mallincam Xtreme that I began using it even under dark skies, like in Chiefland.

For a typical Chiefland Astronomy Village run, I’d set up my NexStar 11GPS, Mallincam (Stellacam in the beginning), and sit under a tent canopy until three or four in the morning, controlling camera and telescope with a laptop PC running SkyTools 3, NexRemote, and the Mallican control software. I considered it a poor evening if I didn’t log and record at least 100 objects. In a typical three-night CAV visit I could easily bag 300 of the list’s faint fuzzies.

So, I basically wound up doing nothing but video during the over three years of the Herschel Project. It was fun, but after that much of it I was glad when it was “fun is fun, but done is done.” After crossing the finish line, I wanted something different, which turned out to be DSLR imaging most of the time and visual the rest of the time. There’s also no doubt the changes I’ve been through personally over the last three years have meant that, while I’m still an enthusiastic amateur astronomer, I’m quite not as hardcore as I was during the go-go days of the Project and not as apt to set up the ton of gear a video run requires.

Anyhow, as I mounted the old Xtreme on the rear cell of the C8, some great memories of the height of the Project came flooding back. All those evenings at Chiefland counting Herschel galaxies by the score in places where I’d never seen a single galaxy, like the wilds of Boötes.

The more I thought about it, though, the more astronomy video seemed to be mostly a creature of the Herschel Project for me—even though I’d become infatuated with the idea six years before the Project began, in 2003, at that year’s Astronomical Convention held in Nashville. There was a Stellacam and Meade 10-inch LX200 SCT set up in the parking lot one night and I couldn’t believe what they pulled in from orange-pink skies near the Nashville airport. I just had to have a Stellacam.

I got one, too, shortly thereafter, and while I used it a fair amount at first, that was just at first. It was soon back in its case for extended periods. I couldn’t find a use for it. The video camera seemed neither fish nor fowl. Lacking the personal and immediate magic of visual observing, but not offering the more finished pictures of “real” astro-cams.

That was the way it was until I started in on the Herschel Project. When I did, everything finally clicked video-wise. As above, I could observe dozens and dozens of objects every clear night, literally tearing through the 2500 DSO list. No, they didn’t look as good as they would have in, say, a long exposure DSLR image, but, frankly, many of those objects, as mentioned above, are bland, small galaxies, and don’t have a lot of pretty to them anyway. As opposed to visual? Man could I go deep with video.

I’d known that even before the H-Project began, like the night at the Deep South Regional Star Gaze when I began imaging Hickson galaxy groups and found my C11 and Stellacam (which was limited to 10-second exposures) could show any Hickson group member visible in the Digitized Sky Survey Plates, which were taken with the 48-inch Schmidt Camera at Mt. Palomar. Yeah, I was going deep, real deep, but without a 30-inch telescope to haul around (and pay for).

When my desire for color led me to replace the Stellacam with a Mallincam Xtreme about of a third of the way through the Herschel Project, I found just how deep I could go. A 1-minute exposure would take me to the realm of quasars, easily recording the ancient objects (see the quasar video at the bottom of the page, which I did in 2015 just before I put the Xtreme away) as well as the little sprites of PGC and UGC galaxies that haunted nearly every field.

Don’t get me wrong; I wasn’t just seeing the ferociously dim, either. There was also detail, plenty of detail, and not just in brighter objects. As the Project was winding down, I hunted Arp (peculiar) galaxies for a while. Not only could I see them, I could almost always at least make out a trace of the odd details that led Halton ARP to add them to his list.

But then the H-Project was over. In addition to me wanting prettier pictures when I took pictures, there was also that “less hardcore” take on our avocation. There is no denying analog video is “stuff” intensive. You have multiple cables, a PC, power supplies, and, if you don’t want to involve frame grabbers, you’ll need a separate monitor to view the video and a DVR of some kind to record your objects. The times I wanted to pull out that amount of gear became fewer and fewer as the H Project receded farther and farther into the rearview mirror.

And there things remained. Oh, I did do a bit of playing with the excellent little Revolution video imager, which I still think is a wonderful buy, and is about as self-contained at kit as you can get, but it had literally been years since the Xtreme gathered photons. Not since that quasar run during my final spring Chiefland expedition in early 2015.

Which brings us to today. What did I think of the Mallincam Xtreme mounted on the back of the Edge 800 now? Some of the old annoyances remained. I don’t like frame grabbers, so I had to drag out a monitor (my old portable DVD player) and a video switch to route signals to it or to the DVR as desired—the camera doesn’t have enough drive to allow it to be hooked to both at the same time without an amplifier. And wouldn’t you know it? The first video cable I hooked between camera and switch turned out to be bad. So it goes in the analog world.

Those were the annoyances, however. The strengths of video were also on display. I was correct about how easy it was to get recognizable pictures quickly. Once I had everything properly hooked up and the bad video cable banished to the trash, it was a snap to produce usable images.

At first, I was afraid I wouldn’t remember how to run the Mallincam control software on the laptop, but it all came back rather quickly. It’s pretty user friendly as esoteric programs go, and I used it a heck of a lot over the years of the Herschel Project. After just a little fiddling around with the settings I was getting surprisingly nice video pictures.

The images I needed for the article safely on the DVR’s SD card, I had time for a little fun before the clouds rolled in, and pointed at some of the late summer DSOs sinking in the west (I absolutely love the new Losmandy’s Gemini 2 goto system). No, the video pictures didn’t have the look of carefully processed DSLR photos, but you know what? They were not bad at all. The stars weren’t grain-of-sand pinpoints, no, but there was nice color, and the frames coming over were not nearly as grainy and noisy as I “remembered.”

So, the final verdict on analog astro-video. REAL astro-video, if you will? I think it still has a place for those of us who own analog cameras, or who are interested in an inexpensive set up like the Revolution Video Imager (a mere 299.00 including a monitor and the other accessories you will need to get going). For those who don’t have an analog camera and want a top-of-the-line one like the Xtreme? Not so much.

The problem is that the base Xtreme is $1300.00, more than some of the new digital video setups (including the Mallincam SkyRaider DS2.3+ and the Infinity from Atik). The premier Mallincam now, the Xterminator, is over $1700.00. While these analog cameras are definitely more sensitive than their digital sisters, that sensitivity does come at the expense of more noise, smaller sensor chips, and images that are more difficult to process. The digicams are actually quite sensitive and more than usable for near real-time video style observing, but they also can be used to produce respectable long integration images.

I do have an Xtreme, however, it still works every bit as good as it did the day I put it away years ago, and I doubt it will stay in its case for another three years. I’m not going to take on the Herschels again, but when I want to capture something way far, far away on the edge of the Great Out There, the Xtreme, the Revolution, and their analog sisters are still the winners hands down.

Note:  You can view these videos full-screen by clicking "Youtube."

Note 2:  Have you heard there is now a place on Facebook where you can buy and sell astro-gear? There is:  https://www.facebook.com/groups/1873482632865645/  It's administered by the good folk at TPI Astro...check it out.



Sunday, August 27, 2017

 

Issue #547: A Losmandy GM811G Comes to Chaos Manor South


Thanks to my recurring back problems I recently put my Celestron C11 Schmidt Cassegrain and my Atlas EQ-6 and CGEM mounts up for sale. If you are a Facebook friend of mine, you know all three went to new owners amazingly quickly. When the dust settled, I was left with a single SCT, my Edge 800, and a single mount, my Celestron AVX, which I like a lot, but…

I recently did some tinkering with the AVX—well computer tinkering, mechanically it is all you can expect from its price class—and that brought some improvement to its tracking ability for deep sky imaging. Tightening up my polar alignment with Sharpcap, and really bearing down on those PHD2 brain icon settings took me from an RMS error of 2” or a bit more on a steady night to 1” or a bit more (or sometimes less) on an evening with superior seeing. The mount is now really all I need for shorter subs, 300-seconds or less, in the backyard. If I have a relatively light payload onboard the VX.

The thing is, however, that I sometimes want to go a little heavier and longer than my 11-pound 900mm SkyWatcher 120 Pro ED refractor. Sometimes I want my Edge 800 SCT for imaging, and sometimes I want my 6-inch f/8 achromatic refractor for visual use. The SCT is not just heavier than the 120, it’s got more focal length to the tune of 1400mm even with the Edge focal reducer in place. The achromatic refractor? While it’s at the limit for me at 25-pounds or so, it’s not too much for the AVX, but I am happier with it on a heavier mount—I’ve used it almost exclusively on the CGEM.

What to do, then? Well, it looked like stingy old me would just have to buy a new mount. One that would not break my back nor my bank account. I did quite a bit of looking and reading and pondering and narrowed my rather small field of candidates to two, the iOptron CEM60 and the Losmandy GM811G.

I’d had the opportunity to see my friend Bruce’s CEM60 in action last summer at the Maine Astronomy Retreat and had been impressed. This innovative “center balanced” GEM looked good, worked great, and at around 2800 dollars (once you buy the nice tri-pier tripod and a couple of other “options”) would not decimate my wallet. Most importantly, iOptron has kept the weight down to a manageable 27-pounds for the mount head but has kept the payload capacity up at an impressive 60-pounds.

The other mount candidate was a new one, the Losmandy GM811G. What’s different about this GEM? It is a hybrid. Take the R.A. assembly of a G11 and mate it with the declination assembly from a GM8. One thing that impressed me about this one other than its good looks—its components are beautifully machined rather than cast—was that it is almost a G11.

The Losmandy G11 is a mount I’ve thought about a lot over the years. In most ways, it seems perfect for me. Or would be if it weren’t just too heavy in these latter days. The G11 head is 35-pounds, approaching Atlas territory, and the tripod is the same 35-pounds, twice what the Atlas and CGEM tripods weigh.

But then came the “almost G11.” The GM811 has a payload capacity (which is stated to be for imaging) of 50-pounds. But it packs that into a 27-pound package just like the CEM60. The relatively light equatorial head would, I thought, allow me to use the mount on Losmandy’s lightweight tripod, the LW, which is a couple of pounds lighter than the Atlas/CGEM 2-inch stainless steel tripod. The GM811 is in the same price range as the CEM60, which made deciding all the more difficult.

Which should I choose? iOptron or Losmandy? I thunk and I thunk and I thunk…

Pluses for the CEM60? It’s, most of all, been on the street long enough now for the bugs to be out. Yes, I know, it’s a mass produced Chinese mount and there can be variation across samples, but from what I can tell, the chance of getting a good one is high. And if you don’t, iOptron is famous for its good customer support. Despite the odd center-balanced trope, the mount is familiar ground for me. The hand control is much like what I am used to with the Celestron and Meade HCs both in layout and operation.

There are minuses, too. Not many, but some. Chief among them for me is that with the CEM60 I would be covering the same old ground, for example hooking the mount to my PC using a darned USB-serial converter. Also, while I think the CEM60 is beautiful, there’s no denying the U.S. made Losmandy looks better with anodized, machined components. Looks aren’t everything, of course. All cats are gray in the dark. But maybe I just wanted something different this time. Something other than the import mounts that have been my bread and butter for over a decade.

What I liked about the GM811G is pretty much laid out above. Great build quality and great looks. And the mount delivers that at a price pretty much identical to what you’d pay for the CEM60. Another plus is the innovative Gemini 2 goto system. Not only do you have a color touch-screen HC, you can link the mount to a computer via serial, USB, or, best of all, Ethernet.

No piece of gear is without its failings, of course, and the GM811 had a few. Mainly having to do with the Gemini 2 system, which I thought might be a minus as well as a plus. It apparently had more than a few developmental problems early on. However, my research quickly convinced me it is now a settled and stable computer. It is somewhat different from what I’m used to with the NexStars and Autostars, though. Couple that with the fact that there’s no manual for it, just a collection of web pages. The one thing that made me hesitant about the Losmandy mount was the Gemini 2.

Luckily, I’d had a chance to see a Gemini equipped G11 in operation fairly recently, and that took away some of my fear. Playing with the hand control simulator on the Gemini 2 web page also helped. A lot. So did spending a couple of days reading and rereading and doing my best to understand the instructions on the Gemini 2 site.

My understanding of how Gemini 2 works began to improve when I grokked the fact that what most often confused me was the author’s, Tom Hilton’s, tendency to tell me more than I really wanted to know. Lots of information is a good thing, usually, but sometimes I just want “how,” I don’t also want “why.” When I came to this realization, I had an easier time understanding what the pages were trying to say, skipping extraneous explanations.

If you’re a Facebook friend, I’ve already spilled the beans as to my final decision there, so I won’t keep the rest of you in suspense. The winner was the Losmandy GM811G—by a nose. I am more than certain I could also have been happy with the CEM60, too.

And so, the wait began, the dreaded wait for new astro-gear to arrive in the brown truck. Looking at UPS Quantum View, I noted that the shipment would consist of three packages, and that I could expect them between 4 and 7 p.m. Monday.

Naturally Monday was a day of me being on pins and needles, and seemed to stretch on forever. At least my prediction that the UPS dude wouldn’t show up till 7 was wrong. The truck was in front of the house well before 5. My old friend Pat’s prognostication also turned out to be wrong, thankfully—he’d predicted that I’d probably only get two out of the three boxes on Monday. 

Three sizable but not enormous packages were soon in the front hall. Just as with the CGEM, I thought the tall one, which was kinda banged up, must contain the tripod. The heaviest must be the mount head, and the next heaviest surely was the counterweight. Time to dig in.

The box containing the CGEM head had been so heavy I’d had to slide it along on the floor (on a towel) for part of the way to get it to the Sunroom, my usual staging area. Not this time. The equivalent GM811 box was a little heavy, but not too heavy. The box that I presumed contained the tripod was positively light.

In the Sunroom, following my usual procedure, I began with the tripod (I did indeed choose the LW option). It was well packed and hadn’t suffered any damage at all, no thanks to the tender mercies of UPS. All I had to do was spread the tripod legs, tighten three knob-headed bolts, and I was done.

Then there was the mount itself. That had to be what was in the heaviest box. Indeed, it was. Well, that and a positively enormous counterweight bar, a stainless-steel job 1.25-inches in diameter, considerably larger (and heavier) than the skinny counterweight shafts on my old Synta mounts. Now for the payoff, the GM811G itself.

I pulled the mount, which was in a plastic bag, out of the box (which was full of those cornstarch packing peanuts that my young feline, Wilbur, immediately began eating) and put the EQ head on the seat of a chair so I could free it from its plastic bag. When it was out, I was bowled over by the GEM’s appearance. For someone used to the cast aluminum of Chinese mounts, the GM811 was quite a revelation, a machined beauty with no plastic. Man, those engraved R.A. and declination setting circles are beautiful. I don’t know what I’ll do with them, but they sure are pretty.

Also in the box was a couple of pages of brief assembly instructions. Brief, but sufficient. With this mount, it’s pretty obvious where everything goes and how. I am sometimes mechanically challenged, but I had no problem putting everything together and really didn’t even need instructions.

The mount head slides into the tripod head and fastens in place with three stainless allen bolts. When I lifted the mount, and slid it into the tripod, I was again impressed. It fitted into the tripod head easily and precisely; there was no fiddling around required. Same for all the bolts and bolt holes on the mount. They threaded in easily without any fuss at all.

Mount secure, I threaded on that big counterweight bar and opened the final box. Inside was an 11-pound Losmandy counterweight and assorted hardware including a toe-saver for the counterweight bar and a set of allen wrenches—all the bolts on the mount are hex-headed allen bolts.  Finally, there was the Gemini 2 computer, the hand control, the HC's coiled cable, a cigarette lighter plug style DC power cable, and the optional 15-volt AC supply I’d ordered. I might run the 811 on batteries on occasion, but I will probably use it on AC most of the time.

Time to get it going—in the house anyway. It was raining as I assembled the 811, and there was absolutely no chance of me using it in the backyard on this night. Or the next. Or the next. In a way, that was probably a good thing. It gave me a chance to figure out the Gemini 2 system in the air-conditioned comfort of the sunroom.

When I’d ordered the mount, I’d been torn about whether or not to order a second counterweight with it. Would one 11-pounder be enough for my 120mm APO or my Edge 800? I needn’t have worried. With the 120 onboard, I had to move the counterweight almost to the top of its travel to balance thanks to that enormous counterweight bar.

Next, I plugged the R.A. and declination cables, which are terminated with DIN connectors, into their respective receptacles on the Gemini computer and motors. The motors on the GM811 are, by the way, the new “tucked” style. They are kinda flipped around from the way they used to be, meaning there is little or no chance of collisions.

Other than that, all I had to do to get ready was mount the Gemini 2 computer to the tripod with a couple of bolts, plug the hand control cable into the hand control and into the proper RJ plug on the Gemini, and attach the AC power supply.

So, here we were at rubber meets road time.  I turned on the power switch and the HC greeted me with a color splash page and then offered to let me calibrate the touch screen. The Gemini 2 instruction sheet informed me that it had been calibrated at the factory, however, and that calibration probably wouldn’t need to be done again, so I skipped that and was soon looking at the startup page.

There, you have several options including Quick Start, Cold Start, and Warm Start. I chose Quick Start, which takes you through the process of entering the things all HCs must know—latitude, longitude, time zone, etc., etc. That was easy enough to do, and I was able to select and enter everything by just touching the screen. Miss Dorothy, seeing what I was doing, found me a stylus designed for use with smart phones, however, and that made using the touch screen more precise. Especially when selecting smaller items like objects in a catalog list.

Once I was done entering the needed info, I thought I’d do a couple of gotos, fake gotos, to ensure everything was more or less well. With the 120mm refractor in the home position, pointed “north” with the counterweight bar down, I told the 811 to go to Arcturus. Off the mount went, and wound up pointing in roughly the proper direction given Arcturus’ current position.

How did she sound? Pretty loud. Not as loud as my CGEM, but loud enough. At first I thought I might need to adjust the worm gears as some new owners have reported they needed to do (on a certain Internet astro-forum), but I didn’t get any stalls or other errors, and decided that wasn’t necessary. Let’s face it, servo motors, which the Losmandy mounts use, are just naturally louder than steppers. The sound level wasn’t helped by the mount’s position inside near a brick wall, either.

And the rain continued to fall. I did get some more things accomplished indoors, however, installing the Gemini 2 ASCOM driver so I could use the mount with my beloved Stellarium, and getting the Ethernet interface sorted. While the Gemini 2 can communicate with a computer over either serial, USB, or Ethernet connections, the Gemini 2 folks strongly suggest using Ethernet. I am no stranger to working with LANs and Ethernet, so I thought I might as well go that route.

Wednesday, my movie day, I stopped at BestBuy on the way home and picked up an Ethernet cable. Modern PCs don’t care whether you use a “patch” or “crossover” cable, so I just bought what BestBuy had in the length I wanted, a 14-foot CAT 6 patch cable.

Standing in a long line at BestBuy turned out to be the hardest part of getting the mount working with Ethernet. Back home, I entered an IP address and a few other things in the laptop’s network setup, typed in http://gemini/, and was soon looking at the mount’s web page. You can do quite a few things using the web interface, including going to objects via a nice onscreen HC, and accomplishing many setup/housekeeping tasks for the mount. I wanted Stellarium in the mix, though.

That turned out to be even easier to set up than Ethernet. I downloaded and installed the Gemini 2 ASCOM driver (which requires the latest version of the ASCOM platform), selected it in StellariumScope, configured a few things in its set up window, and was soon sending the mount on fake gotos from Stellarium’s beautiful sky map. The Gemini 2 driver works perfectly with Stellarium and StellariumScope, and can talk to the mount using Ethernet or serial interfaces. There’s also a driver that allows you to use it with a USB connection if desired.

Then Wednesday evening came and with it clearing. I really wanted to hit the backyard, but I didn’t. It had rained at sundown, and the backyard was a damp, buggy, and humid mess. I also had a road-trip scheduled for the morrow. Dorothy and I would be going to Huntsville for the famous Huntsville Hamfest and to visit the Space and Rocket Center, so I didn’t want to stay up all night long playing “How the heck do I get this darned mount to work?”

On our return Saturday night, the sky was kinda-sorta OK, but very hazy. Unfortunately, it was already getting dark and I was positively bushed after the drive. Sunday was predicted to be better weather-wise anyway, so I put off the mount’s acid test for yet another day.

Sunday found me both excited and a little scared. The mount looked beautiful and seemed to work well, but that was inside. How would it do under the stars? The GM811 was new, and you know how it usually goes with new gear out in the backyard for the first time. I expected frustration—if not disaster—aided and abetted by sweltering nighttime temps, high humidity, and flocks of mosquitoes.

I was wrong. This was the smoothest first light run I can remember having with any mount. Even to include my CGEM, which, given its NexStar HC, was a known quantity for me. Admittedly, I did keep it simple. I didn't try to take pictures or auto-guide or anything; that will be for next time; I just wanted to polar align the mount, get it goto aligned, and play around in the hazy and humid sky a bit.

As soon as there was a little shade on my accustomed observing location in the yard late Sunday afternoon, I got the mount assembled with the SkyWatcher refractor onboard.  I sure was happy I’d chosen that LW tripod. It was less of a strain on my back than even the standard Synta/Celestron tripods are. The mount head? It was somewhat of a handful, but considerably easier to lift than the CGEM or Atlas.  

There wasn’t much to assembly in the field. The bolts that hold the mount to the tripod can stay threaded into the mount, just loosened. Unless you are traveling, you can leave the Gemini 2 computer attached to the tripod. Other than attaching mount to tripod, counterweight to mount, and telescope to mount (the GM811 will accept either a Vixen or Losmandy “D” dovetail), all I had to do with plug in the R.A. and dec cables, the power supply, and the hand control. I’d decided to leave the PC for some other night.

Any mount needs to be decently balanced, so that was the next step after assembly. Balancing the GM811G was a positive joy.  With the friction clutches disengaged, the mount is free-wheeling in both declination and R.A. There was most assuredly no need to guess at balance as I used to have to do with my old CG5’s dec axis. 

After Polaris winked on, it was time for polar alignment. I moved the scope slightly off north in declination to open up the hole in the counterweight bar so I could center Polaris in the hollow polar bore (I chose not to order the polar alignment scope). I then returned the tube to declination 90 and used Sharpcap’s polar alignment tool to dial in the pole.

Polar aligning the mount using Sharpcap, my wide-field guide scope, and my QHY5L-II guide camera was a snap. The GM811’s azimuth adjusters, especially, are just so much better than those on many of the Chinese mounts. The mount’s altitude adjustment requires you loosen four allen bolts, but that was not a big pain, and the mount stayed where it was in altitude when I tightened them back up again. In the interest of keeping my polar alignment good for a few days, I placed my Celestron vibration suppression pads under each leg. Three paving blocks would work just as well, however—or probably better.

Following polar alignment, I put the mount back in home position using a carpenter's level to ensure the counterweight bar was straight down and the tube pointed straight north. Then it was time.

I turned on the Gemini 2 computer and asked to build a model. What I did, as Losmandy suggests in their (excellent) YouTube videos, was align on three stars in the west (where I'd be doing most of my looking) and one in the east.

I chose Arcturus as my first star, and when the slew stopped, it was in the field of my 12mm reticle eyepiece. Centered it and added Dubhe and Mizar. The touch-screen direction buttons took a little getting used to, but after the first three stars I was already used to them. I never felt moved to use the “tactile” buttons on the reverse face of the HC. After lining up on the stars in the west, I selected "east" in the model screen and added Deneb to the model (I didn't do an east model, just added a star in the east to the west model to it to make pointing better if I crossed the Meridian). 

I got rid of the reticle eyepiece and inserted a 13mm wide-field. Then, I went to the “goto catalog objects” screen, selected “Messier,” and told the 811 to go to M3. The mount slewed, the hand control declared "Goto done," and with some trepidation I went to the eyepiece. There was the big glob sitting dead center in the eyepiece, shining bravely through the haze and light pollution. I followed M3 with M13, M15, M27, and as many others as I could think of. The Gemini 2 never missed, not even on objects east of the Meridian. 

At this point I was literally drenched in sweat and the bugs were biting. There was just nothing for it; it was that dreaded time, time to pull the big switch. I could have parked the scope and reused my alignment the next run, but the somewhat dire weather forecast suggested I'd be dissembling the mount and scope and returning them to the Sunroom on the morrow, so I didn't park, just killed the power.

So, were there any problems or hiccups? Only one. I need to change the 811’s safety limits a bit. The safety limits determine where the mount is in regard to the Meridian when it does a Meridian flip, when it changes sides from east to west or vice-versa. Get too close to the Meridian before doing that during a goto and a longer-tubed telescope can bump into the tripod. As my f/7 refractor threatened to do when I sent it to M57, which was near the Zenith. I had to push the "stop" button on the HC to prevent a collision. I just need to tell Gemini that it needs to do the flip a little sooner than what is dictated by the default settings.

Otherwise, I need to devise an accessory tray of some kind for the LW tripod, which doesn’t have one. On this first night, I settled for setting up a folding aluminum camp table next to the tripod to hold the HC, the mount power supply, and the power brick for the DewBuster heaters. 

Next time? I intend to see how the new baby tracks and guides. Which is the ultimate test for any telescope mount. We shall see, but based on my first light experience, I believe this is the beginning of a beautiful friendship.


Sunday, August 06, 2017

 

Issue #546: Two Down, One to Go...



And, so, my C11 OTA has been sold. I'm so happy it, like the Atlas, could go to a friend.

One more then, my friends, one more, a CGEM mount. I have absolutely loved using this Celestron German equatorial, but with my back twinging today, I know I have to let it go the way of the Atlas. If you've been following this saga on Facebook and here on blog, you know that after an accident, a fall, I had three years ago, I began having intermittent back problems. They come and they go, and one thing I have learned is not to aggravate them. Especially by lifting 40-pound GEM heads onto tripods.

Case in point? Last week, I was testing my Atlas EQ-G, which would be the first piece of "too heavy" gear to go up for sale. I was careful while putting it on its tripod and all seemed well. I had a lot of fun taking pictures with the mount, and had almost convinced myself to hang onto it. Until, when I was disassembling the Atlas after three days in the backyard, I--yep--aggravated my poor back again despite my caution. I knew then that both the Atlas and the CGEM just had to go.

As for the current item, my CGEM, I've had a lot of fun with it in the couple of years I had it and will miss it. The mount never failed me, never prevented me from doing what I wanted to do in video, visual observing and long exposure deep sky imaging. You can read about some of our exploits here and here. Certainly I'll be sorry to see the mount go, but I plan to, as I mentioned a while back, replace it with a lighter GEM with a similar payload capacity.

Anyway, the CGEM is just over two years old and includes the standard NexStar hand controller, a DC power cord, AND the optional (and not exactly inexpensive) 5-amp Celestron AC power supply. The counterweight is the single 17-pound job normally included with the mount, but any CG5/Synta type counterweight will work on this mount.

Like most NexStars, the CGEM has outstanding goto accuracy. It also guides very well. Until my back began to discourage me from using it, this was my primary astrophotography and visual mount. It carried a C11 or a 6-inch f/8 refractor without a problem. Notable is that the mount was tall enough that my f/8 refractor never threatened to bump into a tripod leg no matter where I was pointed in the sky.

This is priced to MOVE at $800.00, little more than half its price two years ago. Like the Atlas, this is a PICKUP ONLY item, but, as with them, I am willing to drive a reasonable distance to meet somebody--New Orleans, Montgomery, Pensacola, Panama City, etc.

Please note that the TPI spreader shown in some of the pictures is NOT included. I have moved that to my AVX.

Oh, one last thing to add to the pile of loot. I've realized that after I sell the CGEM, I'll have no further use for my ADM Vixen to Losmandy adapter, so that goes with the mount too.

If you're interested, the best way to contact me is via Facebook Messenger. I do still monitor my old email addy at rmollise@bellsouth.net, however... If you think the CGEM might be just the thing for your observing program, I urge you to contact me without delay. It won't, I presume, last at this price.

Sunday, July 30, 2017

 

Issue #545: Good, Old EQ-6…


Actually, I could have called this issue “Lo, There Shall be an Ending”—Part II. If you’ve read the linked post, you know that for a number of reasons I been thinning out my telescope and mount herd. I got rid of a bunch of stuff in the weeks following that article’s posting, and I thought I was in a good spot, finally, with astronomy gear I could and would use. Well, you know what they say about “Best Laid Plans,” doncha?

I liked my Celestron CGEM mount a lot. It had been a good performer, guiding well and not exhibiting any of the problems some of these Celestron GEMs—mostly earlier examples—have been heir to. Then trouble began. Actually, this trouble started a year before I bought the CGEM.

I took a fall at Chaos Manor South one afternoon not long after we moved out three years ago. The details? Let’s just say it was a boneheaded stunt. I fell on my back and right onto the concrete front steps of the Old Manse. Ouch! right? But while I was bruised and sore, I thought I’d dodged a bullet—until last summer.

Summer of 2016 bought a spate of back problems that just wouldn’t quit. Until they did rather abruptly a month or so after their inception. I was again fine until the beginning of this summer. The latest installment of My Aching Back began following an afternoon when I set up the CGEM in the backyard, lifting the 40-pound plus mount head onto its tripod.

The next morning my back pain returned—big-time—and I was pretty sure what had caused it. I'd been careful lifting the CGEM, I thought, but apparently not careful enough, and again went through weeks of suffering. End result? I won’t say I’m scared of setting up the CGEM…but… OK, I’ll say it: I am scared to do that. I haven’t used the mount in months and don’t believe I’m going to use it much ever again without some outstandingly good reason—something far beyond just wanting to take deep sky snapshots.

It seemed to me, then, that it was time for, yes, “Lo There Shall be an Ending: Part 2.”. The CGEM will have to be sold, I’m afraid. I also still have my nine-year-old Atlas EQ-6, which I’ve been holding onto as a backup for the CGEM. It is only a little lighter than the Celestron mount, so I’ve reluctantly decided it must depart as well. Alas, the same goes for my beloved carbon fiber tube C11, which I am also hesitant to wrestle with now.

Don’t despair for me, however. I intend to replace the two mounts with a single lighter one with comparable or higher payload capacity—maybe a Losmandy GM-811G or an iOptron CEM60. Mounts that will accommodate my Edge 800 better for imaging than my Celestron Advanced VX mount can, but which I won’t be afraid of lifting. It does require me to spend more money on the replacement than I spent on either the CGEM or Atlas, but even penny-pinching me is ready to dole out money for a mount that will accommodate my heaviest scopes, but that I need not fear using now or in the coming years.

M15 with C8 + Atlas EQ-6...
Lighter weight but as much (or usually more) payload capacity is the payoff when you go to the next mount price tier above the CGEM and EQ-6. I’m not saying those Synta-made mounts aren’t an incredible value—they are—but increased weight is the penalty for both respectable payload capacities and low prices.

While I’d used the CGEM early this summer, I hadn’t done anything with the Atlas for a couple of years, not since the Peach State Star Gaze of 2015. I was their Keynote Speaker that year, and because of the event’s relative closeness in Georgia I was willing to drive up rather than have them fly me in. So, I was able to take the EQ-6 and a couple of telescopes with me. The mount performed well, but that was then. I didn’t want to sell Atlas to someone without giving him a through checkout, which I began doing one recent and somewhat cloud-free night.

I decided to recount my process of setting up, aligning, and interfacing the Atlas EQ-6 here, since I thought that might be instructive for those of you considering buying one or who are new to the SynScan mounts—the Atlas EQ-6, the Sirius HEQ-5, and their sisters—sold under the Orion and SkyWatcher brand names.

The first thing you gotta do if you wanna play telescopes with an Atlas is get the big equatorial head onto the tripod. Following my debacle with the CGEM earlier this year, you can bet your freaking bippy I was cautious. I carried the head to the tripod, which I’d already assembled, leveled, and oriented with its azimuth alignment peg north, in a plastic case with two good handles (from Walmart, natch). I was awfully, awfully careful to lift with my legs, not my back, when I pulled the mount out of the shallow box.

How bad was it? I didn’t like doing it, but I didn’t strain anything. The mount is actually a little easier to get on the tripod than the CGEM in my opinion. Something about its shape seems easier to hold onto. Also, its counterweight bar, which is slightly slimmer than that of the CGEM, can be retracted into the mount, and I found doing so made the head less awkward to lift.

M33 with William Optics 80 Fluorite + Atlas EQ-6...
With the R.A. lock locked securely to keep the mount from flopping around, I hoisted the head onto the tripod, aligning the peg on the tripod with the azimuth adjuster assembly on the mount, lowered the GEM head onto the tripod and secured it with the tripod’s threaded bolt (I leave that slightly loose till polar alignment is done).

Mount safe on tripod, I proceeded to do the usual set up things: Extend counterweight bar and load one Synta 11-pound “pancake” counterweight on it—all that is needed for my 5-inch refractor. Place telescope in the Atlas’ Vixen style saddle and secure it with two lock bolts. Attach hand control and power cords, taking care to thread the power cord through the mount’s strain relief widget.

Taking care to dress and secure the power cord is important. The Synta power cables are notorious for losing their connections, the earlier cables, anyway. As on the CGEM, the power receptacle rotates with the Atlas’ RA axis, and the cord tends to become loose or even disconnected. That is the reason Celestron (Synta) used a power receptacle with a threaded collar on the CGEM when that re-design of the EQ-6 was undertaken. The latest EQ-6es, the EQ-6 Rs, also have that feature.

After balancing the telescope in RA and declination (it’s best to have the EQ-6 very slightly east heavy in RA for best tracking during photography, but that is not as critical as it is with mounts in the CG5 class), comes a fairly important operation, setting the mount to home position.

The EQ-6 has neither position switches nor alignment marks, so it is up to you to place the mount accurately in “home” position. That is necessary to allow the mount (which has no encoders; it just counts stepper motor steps) to know where it starts from. Technically, I suppose, after you accurately goto align the mount, how good or bad your home position setting was should no longer matter. It should just help the mount land near the initial alignment star. Nevertheless, at times it sure seems that the more care I take with setting home position, the more accurate my gotos are. Go figure.

Home position for the EQ-6 is with the telescope pointed north and the counterweight bar straight down. It’s easy to achieve this accurately using a small carpenter’s level. Set the mount to 90-degrees in RA with the counterweight bar on the left and the scope on the right as viewed standing behind the mount. Use the level to get the counterweight bar as level as possible. When that is done, lock the RA lock, loosen the RA circle, and set it to “6” using the scale appropriate for your hemisphere; the upper one is for the Northern Hemisphere.

Ready for testing!
Next take care of declination. With the mount still positioned with the counterweight bar level, undo the declination lock and level the tube. Then, set the declination setting circle to the value shown on the mount’s latitude (elevation scale). I am at 30 degrees latitude, so my elevation scale is on 30, and I set the declination circle to thirty degrees.

Now to actually set home position. Undo the RA lock and move the mount in that axis until the RA setting circle reads zero. Then, do the same for declination: unlock it and move the scope in declination until it reads zero, too. If you did everything correctly, the mount should be in accurate home position with the counterweight bar down and the tube pointing due north. After a couple of times, this procedure will become second nature.

Next up is polar alignment. Unlike with the Celestron branded mounts, the accuracy of polar alignment affects the accuracy of gotos, so try to do a good job. I use the Sharpcap program’s polar alignment tool to get a dead-on polar alignment, but the EQ-6’s included polar scope can do OK. You should go beyond the simple “match the constellations” polar alignment outlined in the manual, however. See this article for a simple to do but more effective method of polar borescope alignment.

Can’t see Polaris? The SynScan hand control now includes an AllStar Polar Alignment Procedure in the Align menu (it will not show up until you complete the goto alignment). See the manual for details. I understand this procedure can yield an alignment at least as good as a careful polar scope alignment, just like ASPA on the Celestron branded mounts. I have not used it enough to be able to testify to its accuracy, however.

With my mount in home position and polar aligned, it was time to do the goto alignment. Once you get past time, date, location, etc. in the hand control, it will ask if you want to proceed to alignment. You do, but the question then becomes “Which alignment?” since you have three main options, One Star, Two Star, and Three Star.

One Star:  You line up one measly star and hit enter. Choose this option if your mount is well polar aligned and you’ll be working in a relatively small area of the sky. Near the alignment star, you’ll get good gotos, and they should be OK, at least, on the same side of the Meridian as the alignment star. On the other side of the Meridian, your goto quality will likely decrease. It may also suffer toward the horizons and at large distances from the alignment star, even on the same side of the Meridian as that star.

Two Star:  Use a two-star alignment, centering two alignment stars, if you want to range a little more widely afield in the sky. Gotos should be good everywhere, assuming the telescope doesn’t display a lot of cone error, that is, its optical axis is pretty much in line with the mount’s polar axis.

EQMOD with settings screen...
If your scope does have some cone error? Well, you can try shimming it in the saddle to eliminate that, but a Three Star alignment is an easier go, I guess. In this method, you center an additional star, a third star, which will be on the opposite side of the Meridian from the other two.

So, there I was out in the backyard wanting to give old Atlas a clean bill of health. Since I have often used a Schmidt Cassegrain on this mount, I am accustomed to doing a Three-Star. Even if the tube itself doesn’t display much cone error, mirror flop due to the SCTs moving mirror focusing system can introduce some error anyway. However… I wasn’t really in the mood for a Three Star on this evening.

The day had started out hot, humid, and partly cloudy. By nightfall it was just about as hot, even more cloudy, and seemed stickier and more humid than ever. Despite the presence of my Thermacell bug repeller, the mosquitoes were threatening to carry me off. I wanted to be done and done quick. A One-Star it would be. Frankly, I often use this alignment method anyway. I most often employ the Atlas for imaging, and usually only do one or two targets a night—typically targets in the same general area of the sky. A One Star alignment on a nearby bright star is all I need.

Alrighty then. I told the SynScan I wanted to align, and selected One Star. I then scrolled through the available stars until I got to Vega, selected it, and, after the slew stopped (Vega was in the finder but not the main eyepiece), I centered the star using the up and right keys—just like with a Celestron—which is what you’re instructed to do with current SynScan firmware.

My results after the HC declared “Alignment Successful”? What was in the immediate area? There was M13. I punched that in, hit enter a couple of times, and the mount slewed that way. When it stopped and beeped, there was a little fuzz spot dead center in the field. Now, this was a 40mm (Plössl) eyepiece, mind you, but one with a fairly narrow AFOV, so there wasn’t a whole lot of true field. Also, I’d done the One Star with this eyepiece rather than with a high-power reticle ocular (recommended) because I was lazy. All things considered, that was pretty impressive goto-accuracy, I thought.

After M13, I decided to see what the mount would do on the other side of the sky. Arcturus was in the eyepiece, but off toward the field edge. So was Mizar.  That was just what I’d expected. Back in the eastern half of the heavens, M57 was dead center. So was M13 once more, when I decided to take one last look at it before adjourning to the cool den.

EQMOD connection with USB EQDIR cable...
Any other goto alignment tips? Try to adhere to the “rules” for alignment star choice given in the manual. Especially the one that says that stars one and two in a two or three-star alignment should be at least 3 hours of right ascension apart (that is, separated by 45 angular degrees east-west if at all possible). The current SynScan firmware does a better job of picking alignment stars than it used to, but keep these rules in mind. Try not to use a star near the horizon or the zenith, for sure.

Still getting gotos that are “off”? Try PAE, “Pointing Accuracy Enhancement.” See the SynScan controller manual for details, but this allow you to enter multiple additional alignment points all across the sky. I don’t often use PAE, since my telescope and camera combos give wide enough fields that the mount doesn’t usually miss if I’ve been careful with setup and alignment, but I have found it to come in handy a time or two.

Anyhow, fairly assured the Atlas was still in good working order, I parked it, covered mount and scope with my Telegizmos cover, and headed for the blessed coolness of the house. I wasn’t completely done, though. Next, I wanted to test the mount with a laptop, sending it on gotos with Stellarium and StellariumScope. But that was a task for another evening. I was covered in sweat, suffering from a summer cold, and despite my success with the Atlas was just this side of “out of sorts.”

As the Sun sank on evening two of the EQ-6 check-ride, the sky was not looking good, not good at all. Not completely cloudy, no, but hazy with large swathes of thin clouds slowly drifting through. Still, I figured it would be good enough for stage 2, making sure the mount would still goto its gotos under control by a laptop computer.

One thing I wanted to try in that regard was the new SkyWatcher ASCOM driver. Previously, I’d used a Celestron driver for the EQ-6. That worked fine, no problem, but recently, with the advent of the new Celestron unified driver, support for the Celestron scopes had been discontinued, I had been told. I could simply have used an older Celestron driver, but I wanted to see how the SkyWatcher one worked.

EQMOD's normal display...
With my Scopestuff SynScan serial cable plugged into the base of the hand control and the other into my KeySpan USB-Serial converter, I proceeded to fire up the Stellarium/StellariumScope combo, which is about all I use to control my goto scopes these days. Hokay, selected the new SkyWatcher driver, hit Connect, and immediately got a warning about my hand control. Said text informed me that the driver wouldn’t work with a version 2 HC, needing at least a Version 3 or 4. Rut-roh.

I was puzzled since I do have a version 3 HC. It doesn’t have the very latest firmware loaded, no. It is at v3.37 instead of the current 3.38, but that is still pretty recent. After I dismissed the warning window, however, everything seemed normal. I was sitting on Vega, and the onscreen scope crosshairs were on Vega as well. I clicked on M13, hit the CTRL + 1 key combo Stellarium uses to initiate gotos, and the mount responded immediately, moving the scope right to M13. The big star-ball, nearly centered in a 13mm Plössl at 75x, actually looked better than I thought it would in the yucky sky.

The same was true of any object I requested. I even let the scope track unattended for a half hour or so to see if the driver would crash, but it didn’t. Verdict? Warning or no warning, the driver worked well.

I took another gander at M13 and a peep at M92, and, as I was pondering whether there was anything else that would look good on such a putrid night, the sky well and truly closed down with a big thud. I covered scope and mount and left the mosquitoes to fend for themselves.

The next morning, I investigated the driver issue further. It turned out that what it was trying to tell me was that I did indeed need SynScan firmware version 3.38 for full operability. I’m not sure which features of the driver might not work with 3.37—goto was fine which is all I care about. At any rate, I am a big fan of “if it ain’t broke, don’t fix it,” and believe I will leave it to the mount’s next owner to decide whether to upgrade the HC to 3.38.

Only one major thing remained on my testing agenda. There’s computer control, and then there is EQMOD. If you’ve got or have been considering buying a SynScan mount I’m sure you’ve heard of that, but what it is is a special ASCOM driver. It doesn’t just send goto commands to the mount, it replaces the SynScan hand controller—much the same as the NexRemote program replaces Celestron’s NexStar HC. I began using EQMOD with the mount not long after I purchased the Atlas in November of 2007, and its capabilities have always impressed me. 

Why would you want to do eliminate the SynScan controller? EQMOD, which was developed by the UK’s Chris Shillito and other talented programmers, adds features the HC is missing. As the years have gone by, features have been added to the SynScan firmware, but it still falls behind the NexStar HC, iOptron’s Gotonova controller, and Meade’s Autostar. But above and beyond adding extra stuff, EQMOD does one very important thing:  it fixes the SynScan mounts’ somewhat lackluster goto performance.

A game pad is a perfect solution for EQMOD scope control...
While the SynScan HC is usually more than adequate for imagers going after one or two targets a night with a fairly wide-field set up, for people cruising to many celestial destinations over the course of an evening—video observers or visual users covering a lot of ground for whatever reason—the SynScan HC’s goto precision or lack thereof can sometimes be frustrating. 

Its shortcomings in this area are mostly the result of its simple goto alignment system. The 1-2-3-star alignment of the HC is comparable to what Celestron GEMs were using almost a decade ago. In contrast, EQMOD features sophisticated alignment algorithms and a system that allows as many alignment points as desired to be added to the alignment model—one, two, or three, is OK, but you can do ten if you want—or fifty.

In order to get the mount working with EQMOD again—I hadn’t used the driver in quite a while, largely because I hadn't used the mount much in a long time—I first of all needed to round up my EQDIR cable. While you can run EQMOD using a serial cable connected to the HC (after enabling the SynScan controller’s “PC Direct” mode, which bypasses the HC), EQMOD is more stable and reliable using an EQDIR cable.

My EQDIR cable, the Shoestring Astronomy USB2EQ6, plugs into the mount’s hand control port on one end, and one of the laptop’s USB ports on the other. That’s possible because it has a built in USB-Serial converter (recommended), but you can get models that plug into an outboard USB – serial converter cable instead. One thing NOT to do? Never connect a standard serial cable to the mount’s HC port. The voltage level will be wrong. That’s the major purpose of the EQDIR cable, converting serial voltage levels to the TTL levels used by the mount’s hand control port. EQDIR cables come in two flavors: one with a DB9 connector for the HC ports of EQ-6 (Atlas) mounts, and one with an RJ connector as on the HEQ-5 and EQ-8 (Sirius/HDX) GEMs.

I wanted to load the latest version of EQMOD, which I obtained from the EQMOD Yahoogroup, which tends to have later versions as compared to the EQMOD Sourceforge page. I also needed to fix EQMOD, which (thanks to me no doubt) had been a little squirrelly the last time I'd used it, I recalled. I suspected the problem lay in EQMOD's .ini file, which is carried over unchanged when you install a new version of the driver.

So, I loaded the new version of EQMOD and then, using the EQMOD Toolbox app that accompanies the driver, I deleted the EQMOD.ini file (if the .ini is deleted, the next time EQMOD is used a new one will be automatically created). Testing with the (included) EQMOD simulator, which is a godsend, showed my weird problems had been banished.

EQMOD is not a standalone program, it is a driver, and must be used in conjunction with a planetarium program. Most people using EQMOD pair it with either Cartes du Ciel or Stellarium, both are good choices, but EQMOD can be used with any ASCOM compatible program.

When the sky finally began to get dark, I plugged the EQDIR cable into Atlas and laptop, turned on the EQ-6, and started StellariumScope and Stellarium. I selected “EQASCOM” in the ASCOM Chooser window, and then pushed the “Properties” button to configure the driver (there’s a separate EQMOD Setup app included with the driver if you want to use that instead). I configured the usual things: com port, baud rate, etc., etc. See the EQMOD Wiki for details.

Assigning gamepad functions...
Ready to go, I checked the “Connect” box in StellariumScope, which brought up the EQMOD control panel. Since I’d already done some configuring inside using the Simulator, all I had to do was unpark the mount which, looking at the Stellarium sky display, was sitting on the North Celestial Pole just as it should have been with the mount in home position (where I’d parked it the previous evening).

Now comes the cool part. I began aligning Atlas, building an alignment model. How do you do that? It couldn’t be simpler:  goto a star (since I was using Stellarium, I did that with the usual CTRL + 1 key combo), center it in the eyepiece, and press Sync in the planetarium program. I did that, choosing six bright stars scattered around the sky. Given the haze and passing clouds, I was pretty lucky to see six bright stars, so that was as many as I did.

What do you do then? That’s it. You goto objects. When you are done for the evening, you park the mount to home and shut everything down. Oh, if you want, you can add a new alignment point at any time over the course of the observing run by going to an object and syncing on it. No special procedure is required.

“OK, Unk, but how do you center a star or other object in the eyepiece? You told us the computer takes the place of the HC. Do you have to have the laptop next to the telescope?” You could do that, centering the alignment target with EQMOD’s onscreen direction buttons, but it is far easier (and more fun) to use a wireless gamepad, just like we used to do with NexRemote.

Almost any PC gamepad will work with EQMOD, and setting up and calibrating one is a simple procedure. In addition to the use of a joystick for scope movement (way better than any telescope hand control’s buttons), you can map gamepad buttons to other EQMOD functions. I, for example, have a button on the gamepad that does the sync, one that unparks the scope, one that parks it, and four that allow me to choose mount slew rates.

So, to sum up, what I did was, start EQMOD, unpark the mount, slew to a bright star, center it with the joystick, double-click the sync button on the gamepad (a double-click is required to prevent you from accidentally syncing when you don’t want to). I did the same for five more bright stars. And that was it.

How was goto performance? Stellar. Anything I asked for from horizon to horizon was in or near the center of a 12mm Plössl. That’s impressive considering the fact that my choice of alignment stars was quite limited. I was pretty good in the east, but, thanks to clouds, in the west all I had was Arcturus and Dubhe.

After alignment, I went to as many targets as I could, given the clouds—maybe twenty or so deep sky objects and stars. I let the rig track unattended for half an hour. I parked the scope, shut down EQMOD, and started everything from the beginning. Never any glitches or problems. Rock solid.

The weather soon degraded to the point where even Vega and Arcturus were invisible, so I somewhat reluctantly shut down. How was I feeling about the Atlas? A little blue. It was like the day I drove my 1996 Toyota Camry (with 250,000 miles on it) to the dealer to trade it in on a new one. When I pulled into Springhill Toyota, the car seemed to whisper, “Daddy, I don’t like this place. Why don’t we go for a nice, long drive instead?” It sure was hard to let go, since the Camry still  ran just as well as she had the day I’d driven her off the lot.

Same with the Atlas, “You don’t want to get rid of me. Why don’t we look at some pretty things in the sky instead? We can even take pictures!” I’ll admit it will be hard to let Atlas go after the mount once again showed me what he can do well and simply. But there’s that back problem. At least I know someone will be getting a great mount and my good, old Atlas will get used as much as it deserves.

Sunday, July 16, 2017

 

Issue #544: To PEC or not to PEC


Me and my trusty Ultima 8 PEC circa 1995...
If you read the last installment of the good old Astro Blog, you know I am a proponent of shorter (60 – 120-second) sub-frame exposures for astrophotography. When appropriate. Like from a light polluted site. There are times when you want to go longer, to 300-second or 600-second or longer sub-frames, however. Say when you are at your dark site and want to pick up as many details in the target object as possible.

Some of you, especially cheapskates like me who use inexpensive mounts like my Celestron Advanced VX German equatorial mount (GEM), are afraid of longer exposures. How can you break the 300-second barrier without getting trailed stars? There are ways to do that fairly easily. Good polar alignment is one. Spending time tweaking the settings in your auto-guide program is another. One other thing that is often overlooked and unused, but which can maybe get you the last step on the road to longer subs, is PEC.

Yeah, PEC, aka “PPEC.” You know what that is doncha? You don’t? Well, PEC, “periodic error correction,” was an idea that came out of the early 1990s, when microprocessors and memory chips not only came down in price, but began to appear in telescopes. I don’t know who originally came up with the idea, but it was a good one.

In those days, we amateurs were still guiding manually. You’d monitor a guide star in the guide scope or off axis guider with a cross-hair reticle eyepiece. When the star wandered away from the center due to the inevitable “periodic” errors in the mount’s gears, or drifted north or south due to polar alignment error, you pushed a button on the hand control (which we still called a hand “paddle”) to move that pesky star back to the cross-hairs. You did this over the duration of a long deep sky photographic exposure, which in the days of film was likely at least half an hour.

The good idea represented by PEC was this:  What if there were a way to record your button pushes? Record your corrections for that periodic error and play them back? That would, if nothing else, make guiding easier. Thanks to the recurring—periodic—nature of the gear error in worm gear sets, which is what most of us were using by then, it sounded like PEC could indeed work.

Again, I am not sure who came up with the PEC idea, but the first people to implement it in a commercial telescope were Celestron, the old American based (though Swiss owned) Celestron  out of Torrance, California. They brought PEC to the market initially with their top of the line C8 Schmidt Cassegrain, the Ultima 8, in a new version of the telescope, the Ultima 8 PEC.

It just so happened that not long after the final and best version of that telescope was released, the 9-volt battery powered Ultima 8 (PEC), I was in the market for a slightly upscale SCT. Well, as upscale as penny-pinching me ever goes. By the spring of 1995, I finally had an Ultima of my own, and after buying a few rather expensive (I thought) accessories like a declination drive motor (optional in those days) and a counterweight and rail for this fork mount scope, I undertook to do some deep sky imaging. I was curious to see if PEC really took the pain out of guiding.

Phd2 guiding graph: VX with auto-guiding + PPEC...
What I found was that it helped. You certainly could not expect to go unguided with the C8 at 1500mm (at f/6.3) for over a minute or two—not long enough to accomplish much with film—but it did make guiding less arduous. You still had to watch the guide star, but if you did a good PEC recording, you would usually be OK if you looked away from the reticle for a moment or your attention wandered. The periodic error was still there, but its magnitude was lessened.

Celestron’s PEC implementation was certainly not the end of manual guiding. Naturally, it only recorded your east-west corrections. Any errors in declination are not periodic; they are due to polar alignment error or seeing, not periodic error. Too bad I was always rather lazy about polar alignment in those days. That meant I still had to monitor the guide star attentively.

Also, Celestron’s version of PEC left a little to be desired. Mainly because you had to do a brand-new recording every single night. It was a shame you couldn’t save an especially good PEC track for future use. Turn off the scope at the end of the evening, and your PEC recording disappeared into the ozone.

Nevertheless, I used PEC to the end of the film days, and it did improve my photos, no doubt about that. But when electronic cameras and auto-guiding came in, I forgot all about PEC. Yes, there had been improvements in it—Meade and, finally, Celestron had equipped their mounts with PPEC, permanent periodic error correction. With PPEC, your recording was preserved through power cycles.  But why worry with PEC since you had a guide camera and a computer watching that guide star now?

There was also an old wives’ tale making the rounds. That PEC and an auto-guider would FIGHT each other. That the auto guider and PEC would conflict, one wanting to correct this much and the other that much; one wanting to go in this direction, and the other in that. Some of those old wives were pretty sharp, but this particular tale doesn’t really make a heck of a lot of sense when you think about it. Nevertheless, for a while it was the conventional wisdom astrophotographers embraced. I just sort of accepted it—when I thought about PPEC at all, which was seldom. I was auto-guiding and that always seemed to be enough.

M13: 300-seconds at 900mm f/l...
Well, I thought it was enough, anyway. Auto-guiding with my Advanced VX GEM with my QHY-5L II camera and PHD2 resulted in an RMS error around 2” usually. That was good enough for my most used telescopes, my 80mm and 120mm f/7 ED refractors and my DSLRs. There were some occasional R.A. spikes, though, and at times the error would climb above 2”.

What could I do to improve on that error figure? One thing I’d avoided doing since buying the VX:  spending some time fine-tuning those blasted PHD2 brain settings, the settings in the program that modify the guiding algorithm. I’d pretty much left them on their defaults other than just increasing the guide-step size to accommodate my fast 50mm guide scope.

So, I finally buckled down and took one whole night where I did absolutely nothing but tweak PHD settings. The result? My guiding was now smoother. The spikes were gone, and I rarely had an error above 2”; usually it was 1.5” or just a bit more. The elimination of the spikes meant I could now do longer exposures without having to throw out more than a few subs.

And then I got to thinking. Why should I stop there? If I could get that error just a little lower, it would make imaging with my Edge 800 (at f/7) easier. But how to do that? I’d worked hard on those PHD settings, and had also begun using Sharpcap’s polar alignment tool in lieu of the less accurate ASPA polar alignment in the NexStar HC—that really brought the declination error down.

What else could I do, though? Well, how about PPEC? If it helped A-P’s fancy mounts, which come with factory recorded PPEC to lower their already impressive error figures, why couldn’t it help my plebian (like me) mount?

I decided to find out. Luckily, we were undergoing a strangely cloud-free pause in the usual summer evening thunderstorms. My VX along with my 120mm SkyWatcher ED refractor, Hermione, was still set up in the backyard, polar aligned, goto aligned (hibernated), and ready to rock following the night of my Yearly M13. Since the evening didn’t look that good for imaging—haze and also unsteady seeing in advance of the next storm front—why not devote it to PEC? After all, I’d spent a whole evening getting my PHD2 settings tuned to the VX.

OK, so how exactly would I make a latter-day PEC recording? I’d taken a brief look at the short set of instructions in the VX manual and concluded there really wasn’t much to it. The process wasn’t much different from back in the day except for the fact that PHD2 Guiding would be doing the “button pushing” and not me (thank God). Since I guide via the mount’s auto-guide port with an ST-4 cable, the set up was simple. No need to worry about ASCOM or anything like that.

While the book instructs you to use a bright star for guiding when PEC recording, there’s no reason for that with today’s sensitive guide cameras. I pointed the scope at the field of M57 and there were dozens of good guide star candidates. Some folks will also tell you that for best PEC results you need to make the recording using a star near the Celestial Equator. That is also untrue. It really doesn’t make any difference.

Step one, it appeared, was “indexing,” allowing the mount’s PEC routine to find the worm gear “index,” a marked point on the worm that is picked up by a sensor. For PEC to work, the hand control has to match the gear to the recording every time you use PEC, the gear and the recording must be synchronized. Indexing does that. Anyhow, I selected PEC in the Utility menu, and hit enter. The mount then indexed, which only took a second or two (if the worm has to rotate far to bring the index mark to the sensor, the mount will move slightly). Time to record.

Over at the PC, I started PHD2 guiding on my pre-selected guide star. I gave it a little while to settle down, returned to the mount, and hit “record.” That began the ten-minute process of making the actual PPEC recording. Unlike the old days, there wasn’t anything for me to do. Assured PHD2 was guiding with its usual alacrity, I headed for the den to cool off from the hot and muggy backyard.

M57:  600-seconds...
The rest was rather anti-climactic. I returned outside ten minutes later, and could see from the HC that the recording was done. Just like with a tape recorder, you don’t just record, you play back. I selected the playback function and let her rip, beginning a 600 second exposure of M57 with the main camera, my Canon 400D.

What were the results? Error wise, they weren’t like night and day, but there was a difference. As above, my normal error level with good PHD2 settings and a good polar alignment had been around 1.5”. With PEC playback on, the RMS R.A. and declination error declined to around 1” to about 1.10” with the actual R.A. error almost always well under 1”. While I was slightly out of focus with the main telescope, the stars in the ten-minute exposure were decently round, as were the stars in a 300” exposure of M13 despite the fact that it had crossed the Meridian and the mount was not balanced properly in R.A. for imaging in the west. My verdict? Recording PEC had been nearly effortless and certainly worth it for a noticeable improvement.

Over the last several months, my easy improvements:  PHD settings, polar alignment, and PEC have taken my AVX mount from an average total guiding error of 2 – 2.5” to 1”. While I was getting by before, I am certainly doing better now. And the fact that my guiding is now consistently smooth with no excursions mean I am much, much more able to undertake longer exposures, 300-seconds and above, when appropriate.  My sense is that as long as balance is reasonable, the mount will guide at the above error level for as long as I want to go.

So, am I at the end of my improvements? Maybe, and maybe not. I could certainly leave the AVX alone now. But there is one further “easy” improvement I could essay. My single PEC recording improved the error figure. But averaging several runs and uploading that resulting smoothed curve to the mount might make it even better.

Celestron still offers a free program to do that, “Pec Tool” (even though it hasn’t been updated or publicized in a long time). I may be reaching the point of diminishing returns with the VX—1” RMS error is pretty good for a mount in this class—but it might be worthwhile to take this one last step. I’ll let you know how it goes if I decide to do that (ain’t broke/don’t fix it) and if clear skies ever return this summer. It is, yes, raining hard now.

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