Wednesday, October 21, 2020
#569 Mars Redux
|The ASI120MC, Shorty Barlow, and Meade flip mirror.|
Did I take a peek or two at Mars in 2018? Sure I did, but it wasn’t a very good year for the planet what with the dust storms and all. I’d been hearing, howsomeever, that this year’s apparition was turning out to be a Real Good one.
And….as I thankfully have frequently of late, one afternoon last week I felt the call of the backyard. “Time to get the C8 set up, I reckon.” What would I set up Mrs. Peel, my Celestron Edge 800, for, though? That was obvious. While we are now pulling away from the Red One, when Mars was at opposition on the 6th of October, we were a mere 62 million kilometers from that mysterious world, we won’t be as close again for 15 more years, and the planet is still awfully big and bright.
15 years? That will make your old Unk…well, “15 years older,” and I question whether I’ll be up to getting even an 8-inch SCT into the backyard by then. Frankly, thanks to the injuries I suffered last year, it ain’t exactly a piece of cake for me to get the freaking Advanced VX set up now. That being the case, I figgered I’d better take advantage of this Mars opposition. And I will, y’all, I will. The image you see here will just be the beginning, I hope. As I was during the BIG opposition of 2003, I plan to be in the backyard taking my humble planetary snapshots almost every clear evening.
First step, then, was deciding on the camera to use. Well, that wasn’t much of a decision to make since I really only have one planetary camera these days. Planetary camera? Without going into a lot of detail which will be amply explained by the links above, what you want for taking pictures of the Solar System is a camera with a small sensor which is possessed of many pixels. And you want it to output .avi video. You’ll take as many frames as possible and reasonable and stack those into a finished still image.
|Sky & Telescope's Mars Profiler helps you find your way across Mars. |
That’s when I began hearing about a new mainland Chinese company, ZWO optical. Looking at their offerings, I found they had a camera that appeared might do the job for me, the ZWO ASI120MC, a one-shot color job with a maximum resolution of 1280x 960 (all my other cameras hovered around 640x480). As above, when you’re imaging planets the idea is to take a lot of frames and stack them in the interest of reducing noise and catching moments of good seeing. The 120, ZWO said, was capable of up to 100 frames per second (fps) at lower resolutions and 20fps at max. That sounded right good to me, so I took a chance.
This was before ZWO, which is now one of the top CCD/CMOS astronomy camera vendors, hit the bigtime. When I ordered, they had no U.S. dealer; my little widget had to come all the way from the People’s Republic of China. Which it did in a surprisingly short time.
What was in the box when it appeared on the front porch of the legendary Chaos Manor South and your not-quite-so old Uncle got it into his hot little hands? Well, there was the substantial and, frankly, impressive camera itself. Metal, nicely finished in red. There was also a 1.25-inch nosepiece, a short USB cable, a CD with some software, and an IR block filter to make it easy to get shots with easy to balance color. Heck there was even a fisheye lens for the cam, which some folks have used to turn the 120 into an inexpensive all-sky camera.
Anyhoo, the little camera has been my sole Solar System imager over the last decade. Hey, I don’t aspire to become the next Damian Peach or Chris Go—even if I had the talent and dedication to achieve the results of those masters. As always, Unk is a dabbler. One night, I’m looking at a bright comet with a 3-inch refractor, the next I’m doing deep sky video, the next, spectroscopy. You get the picture. The ZWO proved to be simple to use and has produced results that have pleased me.
Oh, Unk did fib a bit. I do have another camera that would work well on the planets, my QHY5L guide cam. However, it’s black and white. I want color, and if you think your fumbling Uncle is gonna start shooting through RGB filters, you’ve got another think coming. It’s one-shot color all the way ‘round here.
By the way, the 120mc is still readily available from ZWO and their dealers. It’s a little more expensive than mine was, but you do get a little lagniappe for the extra dineros: the camera now sports an ST4 auto-guide output. Is the 120mc color version sensitive enough for guiding? Based on my experience using the camera for short-exposure deep sky imaging, I would say it definitely is. And for planetary use, it is still the bomb. You can get ZWOs with bigger chips these days, but, again, for the planets you don’t need bigger chips. The megapixel range 6mm sensor in this little camera is just right.
Would it still work, though? I hadn’t used the camera in quite a while, and many Windows 10 updates had intervened. Only one way to find out…downloaded the latest driver from ZWO’s website, rounded up a USB “printer” cable, connected it to the laptop and cam, lit off Sharpcap, and she started right up, no problem.
Sharpcap? Yes. While I previously used Firecapture (and before that, the now-forgotten K3CCD Tools), I’ve chosen to move on to Sharpcap for control of my planetary camera. Firecapture is still great, but, for one thing, I am more used to using Sharpcap now, since I fire it up on a regular basis to do polar alignments (its polar alignment tool is flat-out amazing). Also, I might as well get my money’s worth out of the software since I am paying for a subscription to the Pro version Sharpcap. Finally, it is an impressive, professionally executed, frequently updated piece of software.
And so, it was time to put the scope together on one cool if hardly chilly Possum Swamp afternoon. The telescope was, as I’ve done mentioned, Mrs. Peel. To get planetary images that show much detail, you need mucho focal length. Even my girl’s 2000mm would not be enough. I would increase that, however, with a 2x Barlow.
|I began with the ringed wonder.|
There is. The secret is a “flip mirror.” A flip mirror is like a star diagonal, but with a couple of differences. Normally it works just like a diagonal: light enters from the telescope and is diverted 90-degees by a mirror and to the eyepiece. However, a flip mirror includes a knob or lever that allows you to flip the mirror down, out of the light path. Images then go out the back of the diagonal through a camera port. Put an eyepiece in the flip mirror’s eyepiece holder, attach your camera to the camera port, center up the target in the eyepiece, flip the mirror down, and it will be in the field of your camera (flip mirrors are adjustable so you can align the camera and eyepiece views).
A flip mirror makes finding and centering objects at large image scales and with small imaging sensors trivial. Only fly in the ointment? While you can still buy flip mirrors, they are not as plentiful as they once were. They were originally popular with deep sky imagers as well as planetary imagers back in the dark ages. Once DSO astrophotographers went to large chips, they had little further use for flip mirrors, and there was then a reduced demand for them. But you can still find them both new and used. I’m am still chugging along with the 1.25-inch Meade I’ve had for the better part of 20 years.
|Not my fave side of Mars, but there's Olympus Mons!|
Alrighty, then. I did a quick StarSense auto-align (yes, I am too lazy to center a few stars with the hand control these days, folks). Mars was still low and in the trees, so I thought I’d give Saturn a look see. Maybe Jupe, too. I started with the king, old Jupiter. Got him framed nicely, and focused and started exposing. And, in Uncle Rod fashion, I screwed up right out of the gate.
To begin, I forgot one of the first things I learned about planetary imaging way back in the webcam days: aim for the shortest exposure possible; one that yields an onscreen image that looks slightly underexposed. I didn’t. I overexposed Jupiter. However, since I plan to get out at least every couple of nights (giving Mars time to rotate new features into view) I’ll be back to Jupiter soon.
My other foul up? You want plenty of frames, but not too many. Jupiter rotates so rapidly that if you go much over a minute features will actually begin to blur. More importantly, stacking programs like Registax and AutoStakkert will refuse to process videos that are too large. For moi, about 30 – 45 seconds at 20 fps or so is more than good enough. Yes, more frames can yield a less noisy image, but you do reach the point of diminishing returns after about 1000.
|The B.A.A.'s excellent Mars Mapper.|
All you need to do to capture Mars or whatever is set exposure and gain till you get that slightly underexposed look onscreen, open the capture menu, click “start capture,” tell Sharpcap how long or how many frames, and hit the go button. When your sequence completes, the program conveniently places your file in a folder called “Sharpcap Captures” on your desktop. Whether you go for Sharpcap Pro or the basic version, the software is highly recommended by your old Uncle, and if he can get pretty good results with it, you surely can.
When Mars finally got high enough to fool with at about 21:00 local, I went there, touched up focus and ran off a few sequences. Now, what was on display was not my favorite side of Mars. I find the Mare Serenium “streak” slightly blah. However, it’s not entirely without its points of interest. On this steady night, even before I processed the images, I could see Olympus Mons was visible. Of course, Mars’ rapidly shrinking polar ice cap was on stark display.
“Mare Serenium?! Unk, I don’t know pea-turkey about that-there!” If you’ve done everything correctly, including when stacking your video frame with Registax or AutoStakkert, and have judiciously applied Registax’s famous wavelet filters, you will be surprised at how much detail you’ve recorded. You obviously need a map to sort out that detail. Ideally, one tailored for the date and time you took your pictures.
A chart just like that “MarsProfiler,” this can be found on Sky & Telescope’s website. It’s actually a little app. You enter the date and time of your image’s acquisition and it will show just what in tarnation you are looking at. While it’s not quite as detailed, I also really, really like the British Astronomical Association’s “MarsMapper.” In some ways I prefer its Mars disk format to S&T’s flat chart, but I find both of these apps absolutely indispensable.
|The beloved Rat-Bat-Spider from Angry Red Planet.|
Then, get out with the scope and get some shots of the Angry Red Planet. Even if you don’t know a thing about processing planetary images right now, you’ll have some video sequences in the can that you can work on next month—or next year—and your results will just get better as you go along.
Unk? I’ve got to teach my university classes tonight, so I may not get back to the 4th stone from the Sun this evening, but I darned sure will tomorrow night. No, it ain’t as good as 2003, but it sure feels a lot like that, muchachos, it sure feels a lot like that.
One thing you can say for your old Uncle Rod? He ain't no piker. Well, he tries not to be one anyways. Two nights after I snapped the image above, I thought I'd give Mars another try. Two days is enough time to give the planet, which has a day only a bit longer than ours, a chance to rotate into a slightly different position so it will reveal a few new features.
|Edge 800 8-inch SCT, ZWO ASI120MC, 6,000mm|
My results? I had to throw out a few sequences due to dust on the sensor chip. Once I noticed that, I moved the planet to a clear spot (I'll clean the ZWO's chip before doing any more work). The remaining sequences I got were easy enough to process, and the resulting final stills, while they darned sure won't win any prizes, are good enough for me; they make me feel like I've come home to Mars once again.
Which I'll admit is sometimes MY Mars. Not the Mars of NASA's rovers, but an old Mars of beautiful princesses, bizarre creatures, and mile-high skyscrapers adorning strange Martian cities. That's what I dreamed of when I shut down the laptop, stowed the bottle of Yell, and dozed away on the couch, anyhow.
Sunday, October 11, 2020
#568 My Yearly M13: 2020
Now, I certainly try to and usually do get out and do astrophotography more than once a freaking year. But long stretches do often separate my sessions. The main reason for that being the weather. As I have oft-opined here, it seems to me imaging-worthy skies have been less common over the last 8 years or so than they used to be. I’d be the last to claim you can make any conclusions about weather trends from a mere 8 years of observations, but that is the way it seems to me.
One thing I do know for sure? In the first decade of this new century I had many mid-summer nights of imaging and observing fun down south in Florida at the Chiefland Astronomy Village. That good summer observing began to dry up around 2012, and Chiefland weather the rest of the year began to decline not long after. That is one of the reasons I have not been back to the fabled CAV in nearly five years. Even the still somewhat hardcore (well, a little) Uncle Rod can only stand so many nights holed up in a cotton-picking Quality Inn under cloudy skies. Unfortunately, it ain’t just Florida skies that now seem worse year-round; the same is true up here on the northern Gulf Coast in Possum Swamp.
Be that as it may be. Resolving to shoot M13 once a year, yeah, ensures I get out with a camera and a telescope at least once between late spring and early autumn. The last time I did some honest-to-God prime focus, long exposure, guided imaging? Wellllll...that was…I can’t exactly remember, y’all, but maybe not since last year's M13.
So it was that once bad old Hurricane Sally had become just an unpleasant memory, and the clouds that had followed in her wake had all flown off, I prepared to shoot my annual portrait of the big glob. Two weeks after the storm, we were enjoying a nice stretch of weather. Plenty of Sun and blue skies with highs in the upper 70s and lows at night in the 50s. While “50s” is a little cool for your aged Unk’s bones, I prefer being a chilled to having the sweat dripping off me and onto the laptop as I try to take deep sky pictures in my bumbling fashion.
So, as October came in, I would be getting out into the backyard with telescope and camera. But which telescope and which camera? As I said last time, I’m lazy in these latter days. What is a pretty much guaranteed way to get recognizable deep sky shots without much effort? Shoot them with a short – medium focal length 80mm APO (color free) refractor. My beloved 80mm William Optic Fluorite f/7.5, “Veronica Lodge,” would fill that bill.
Veronica is elegantly and sturdily built, but still light enough not to challenge my Celestron Advanced VX GEM mount, so that was what I would put her on. The only question in that regard? “Guided or unguided”? The sky Friday before last was clear, but man was it hazy. Haze scatters light, making the light pollution of my suburban backyard worse than it is on a clear and dry evening. That meant I’d probably limit my exposures to two minutes. Since I’d be doing a precise polar alignment, I probably could have gotten away with no guiding at all for 120-second shots. But since I’d have the guide camera with me to do a Sharpcap polar alignment, why not guide?
Scope, check. Mount, check. Camera? I thought that would be my old Canon Rebel. It’s dependable, I have an AC power supply for it, and as things are reckoned today, the 12-year-old camera has relatively large pixels. That ain’t a bad thing in the deep sky imaging game, campers, since “larger pixels” naturally means “more sensitive.”
All that remained was to decide on the software I’d be using. As always, I’d be controlling the Canon and acquiring images with Nebulosity. The program, by Craig Stark, author of the original PHD Guiding, will do anything I need it to do and more including acquiring, stacking, and processing DSLR images. While it was initially intended for use with Canon DSLRs, it also works with many astronomical CCD cameras.
I dunno about you, but when I’m imaging I do not like hanging out at the freaking telescope. I want to sit at the computer and run the show from there. I could have used Celestron’s CPWI program, the successor to NexRemote, which we talked about a couple of weeks back. That would have allowed me to control everything from the laptop including the goto alignment. I don’t have much experience with the program yet, though, and thought it best to keep things a mite simpler.
|The new Cartes du Ciel beta.|
Likely I’d be fussing with the other software, trying to remember what little I ever knew about it. So, instead of CPWI I thought I’d use a nice, friendly, simple planetarium program with an ASCOM driver. ASCOM would give me a little onscreen hand control useful for centering objects in the camera’s frame.
What I’ve used most over the last few years when it comes to PC planetariums is the excellent Stellarium. However, a sentimental favorite, Cartes du Ciel, was, I heard, in a new (beta) version, 4.3. That being the case, I thought I’d give the latest CdC a whirl. I’ve noted quite a bit of traffic on the program’s mailing list of late, so Cartes is obviously more than just still alive.
Guiding? I ain’t used anything but PHD2 since it came out. And I hadn’t used anything before that but the original PHD Guiding since the dark ages when I was photographing the skies with my old self-guiding SBIG black and white astro-CCD. It would be PHD2 Guiding all the way. I had to get it going on a new laptop about a year ago, and was quite not sure I had all the settings correct—I hadn’t used it since then—but I figgered it wouldn’t much matter with short focal length Veronica.
Anything else? Well, I was darned sure glad I checked out Sharpcap the day before my M13 expedition to make sure all was well with it. It turned out my subscription had expired. You see, I use the Pro version (the one with the polar alignment tool). It ain’t freeware, being offered on a yearly subscription basis. Seemed like I had just renewed the program for the very reasonable fee of 15 dollars a year, but, yes, another year had flown by. Anyhoo, it took but a few minutes to get a new subscription and a license in place. Glad I wasn’t blindsided by that in the dark backyard, though.
So, into that backyard I went, setting up in my usual fashion with the scope beside the deck and me and the laptop on the deck. It’s like an observatory for somebody who doesn’t want an observatory: I can leave the telescope set up in my secure backyard for as long as the weather stays nice. Sitting at the patio table under a big umbrella, I’m out of the dew and so is the PC. And I’m just steps from my den where I spend my time while the exposures are clicking off. Oh, I check things once in a while, but watching The Mandalorian on TV while drinking a…uh… “sarsaparilla” is a lot more fun than watching the PHD2 guide graph, friends.
While I hadn’t used Veronica in a long while, she went together smoothly: plunked her into the mount’s Vixen saddle, attached her tube extension to the focuser, put my (excellent) Hotech field flattener into that, and mounted the camera via a, natch, Canon format T-ring.
|Nebulosity doing its thing.|
Whoooeee. I was close to sweating even in the cooling air as the stars winked on. Next order of bidness was polar alignment. I temporarily placed the laptop on a little tray-table next to the scope, plugged the guide scope into the computer’s USB port, and fired up Sharpcap.
How long does a Sharpcap polar alignment take? Maybe 10 minutes first time out. Five minutes or less after that. The process is simple. Set the mount in home position pointing north in declination with the counterweight down. Click in the Tools menu to start the polar alignment.
Sharpcap will expose a few frames and will shortly tell you to rotate 90 degrees in RA. That done, you’ll use the mount’s altitude and azimuth controls to point at the North Celestial pole with the aid of onscreen graphics and text directions (“Move up 12’…”). How accurate is it? Now that it takes refraction into account, I have faith that when it tells me I’m just seconds from the pole that’s just where I am. And my results indicate it is telling the truth. If you have a guide camera, Sharpcap is the obvious cure for the polar alignment blues.
Polar alignment done (the somewhat course altitude/azimuth controls on the AVX make the process more difficult on that mount than on my Losmandy—but it’s not bad), it was time to essay a goto alignment via the StarSense auto-align camera. I’ve never had a problem with the StarSense; it’s always produced an alignment as good as what I can do with the normal hand control. But there are a couple of gotchas to watch out for—one of which your hapless raconteur encountered on this very evening.
|Full sized image.|
‘Twas not to be muchachos. The StarSense did the goto alignment successfully as always, going to four star-fields and plate solving. When it was done, I sent the mount to Vega, which I thought would be a good target for rough focusing. Fired up Nebulosity, started clicking off focus frames and…no Vega did I see. Tried slewing around a little. Nope. No Vega. Sighted along the tube and did some more slewing. Nope, sorry, Charlie.
There was nothing for it. I’d just have to calibrate the StarSense. That is easy if you, unlike your silly Uncle, remember how to do that. Send the mount to a bright star (Vega in my case). Get the star in the field of an eyepiece or camera (I did that by replacing the StarSense with a red dot finder temporarily). Press Align, and use the hand control’s direction buttons to precisely center the star.
That sounds easy. And it is easy if you, unlike Rod, remember to press Align, not Enter. Pressing Enter sent the mount back to where it was in the beginning; where it thought the star oughta be. So, Unk got to start all over from the beginning after biting the bullet and digging out the StarSense manual.
Got ‘er done, and all should have been well. But wouldn’t you know it? Uncle Rod did some assuming, and you know what they say about that word. Once the calibration is done, the HC tells you you need to do another alignment. That’s easy, just press enter and it will be executed automatically. Silly old Rod, however, thought he should set the mount back to home position first—which you do not need to do. You will not be surprised to learn the AVX pointed the scope to the Earth for the first plate solve. Power down, start over from scratch one more time.
|Zoomed in with a crop.|
OK! We was rollin’ now. That’s what Unk thought, anyhow, but the gremlins weren’t quite done with his sorry self. Time to engage Cartes du Ciel. Started the program, connected the ASCOM driver to the mount, clicked M13, and then the slew button, and off we went for the globular. The mount was about halfway there when the computer went fitified with a blue screen of death. I don’t know I’ve ever had that happen with Windows 10, but it sure did happen on this evening.
Luckily, the mount continued to M13 unaffected, I restarted the computer, reconnected all the software, and the laptop was OK from then on. What was the problem? Despite the fact that I was using a beta version of Cartes, I’m guessing the culprit was actually the older ASCOM version I was running, 6.1. By the light of day, I investigated and found some people had had problems with that one. So, I updated to the current v6.5, even though I had had no further problems with Cartes for the remainder of the evening.
Cartes du Ciel? Other than that hiccup, it was wonderful. No, it does not have the pretty sky of Stellarium, but it makes up for that with the legibility of its display in the field, and has many more features for observers than Stellarium, despite me loving that program very much. Go out and get the new CdC; it is another winning version in a long string of winning versions.
The rest of the evening was frankly pedestrian in the extreme. I got PHD2 Guiding doing its thing without a hitch. While the seeing, never good, was degrading as time went by, my errors were just a little worse than 1” with PPEC not turned on. Well, till M13 began to get lower on the horizon after about an hour, and I began to approach 2”. Unfortunately, in October there ain’t much time before the glob begins to get low; especially if, like your fumbling Uncle, you waste at least half an hour before taking your first sub-frame. But the higher guide error toward the end of my sequence was not a problem. Again, an 80mm scope is very forgiving. You almost have to work not to get round stars.
|And...the clouds are back.|
The denouement? Early Saturday evening, I shot a series of T-shirt flats using the sky at dusk as illumination. As I was doing so, I witnessed the darned old clouds begin to flow back in after giving me almost a week’s respite. Not just that...another big storm was shortly threatening the Gulf. So, I was glad I’d got out, full Moon or no (did I mention shortly after my imaging sequence began, a fat Moon began to rise in the east?). That done, I went through the usual processing steps with Neb: debayer both lights and flats. Stack lights and flats into single images and combine master flat and master light into one photo, process using Nebulosity, and do final touchup with Photoshop.
“But what about darks, Unk? You gotta shoot darks, doncha?” I did, Skeezix, but I did that as I was shooting the lights, automatically. I set the Canon Rebel to subtract a dark after every image. It takes twice as long to get through your sequence, but I find doing it that way yields better results. With an uncooled camera like a DSLR, it’s always best to shoot a dark immediately after the light so the sensor is at a similar temperature.
My results? Not so bad. While something like this would never appear in the magazine’s Gallery section (!), I’ve done worse on a hazy night in the suburbs with big Moon rising. Frankly, this year’s shot is at least as good as what I got in 2019 with an LX85 mount and a Meade 8-inch ACF under similar conditions (in late 2019; the blog article didn't appear till January 2020). But you know what? This exercise ain't about results, anyway; it’s about Unk getting his silly old self out under the night sky with a camera and getting back to work, muchachos.