Sunday, November 06, 2011
When it comes to astrophotography, your old Uncle Rod is the perennial beginner. I’ve been trying to take long exposure pictures of the deep sky for over 40 years, and while I’ve had some middling success, you will never, ever see my shots in the Gallery section of Sky & Telescope.
Not that that’s all bad. Since I am still a beginner at heart, albeit one with a lot of experience, I have an easy time writing articles on introductory imaging, like the one I did for Sky & Telescope’s Skywatch annual this year. And despite the fact that I’ve resigned myself to the reality that I will never be a celestial Ansel Adams, I almost always have fun with astrophotography. When the astro-imaging fever is on me, I spend nights and days having a ball taking and processing astrophotos. Our tools have changed from film and darkroom to digital and computer, but the process is still much the same and I still like it.
Another reason for my failure to join the “10-hour exposure through multiple filters” club is that I am the original astro-dilettante. There are many pursuits in our broad avocation I enjoy. Tonight it’s sketching, tomorrow night I’ve got a video camera on the scope, and the night after that I am back to visual work with my wonderful Ethos eyepieces. No, I maybe never get as good at any one of these things as the more single minded, but I think this has kept amateur astronomy eternally fresh for me. There is always something new to try.
|My (excellent) Harbor Freight inverter (the blue thingie).
Ah, yes, the Orion StarShoot autoguider the lovely Miss Dorothy gave me Christmas before last, and which I’d been able to try briefly exactly once. At least it looked good: nice metal body, ST-4 guide output, and an amazingly large sensor (a ½-inch 1.3 megapixel job). The only bummer is that this chip is a CMOS one like those used in consumer digicams, not a CCD. CMOS chips work well for imaging of all kinds, but they are less light sensitive than CCDs. The single time I’d tried the StarShoot, it seemed to pick up stars OK, but that was with a larger aperture guide scope than the 50mm one I’d be using now.
I also wanted to give EQMOD a workout, even if it ain’t so new. I’ve known about this wonderful program for over four years, ever since I bought my Atlas (EQ-6) mount. What’s it do? It’s a telescope control program that runs on a PC and replaces the mount’s SynScan go-to hand controller. It’s a lot like NexRemote, but for Synta-branded scopes. It adds more features and makes some things easier. It, for example, allows you to use a wireless gamepad instead of a wired HC to move the scope and issue some commands. I much prefer a joystick to four stinking little buttons.
While I’ve not just used but written about EQMOD, that was a long time back, and the program has added significant new features since then, including a polar alignment utility. Above all, if I was going to drag out all the imaging gear, I wanted to give it the best possible chance to perform well. Since I’d gotten good results with EQMOD the first time I ever used my Canon DSLR for astrophotography, it made sense to use EQMOD again after a long layoff from DSLRing.
When you think about long exposure digital imaging, you naturally think “lots of gear,” but, honestly, compared to all the stuff I lug out for a video run, a night with a DSLR is actually relaxing gear wise. I can eliminate the DVD recorder, the portable DVD player I use as a video display, several cables, and the big deep cycle marine battery that powers the recorder. I did bring a small 12vdc battery, a lawn tractor battery, and an inverter with me on this run to ensure the netbook had enough power to get through the evening. The StarShoot guide camera draws current from the computer’s USB port, and I was afraid that would shorten the Asus netbook’s normally amazing internal battery life.
My equipment load was lighter, yeah, but not exactly light. In addition to the C8 OTA, the Atlas mount, the new guide scope, and the StarShoot, there was the Canon Rebel DSLR, the remote shutter control widget (needed for older Canon DSLRs), a box full of cables, a wireless gamepad and receiver for EQMOD, and all the usual stuff I need for any run beyond the most informal. Can’t do without multiple accessory cases, DewBuster controller and heaters, dew shield, chair, table, computer shelter, etc., etc., etc. Since this would be a cold night as we judge such things, low 40s, I made sure I brought my heaviest coat and plenty of (disposable) chemical hand warmer packs from Bass Pro.
Since the Sun would go down shortly after 6 p.m., I needed to leave the Old Manse no later than 4:30 to allow plenty of set up time. As I was driving down Government Street in my new truck, Miss Van Pelt, I, as I always do, started playing the “what did I forget” game. Doh! Left my thermos of hot tea and my Monster Energy Drink sitting on the island in Chaos Manor South’s kitchen. I decided I’d keep going. Traffic was bad, and tea or coffee eventually makes me feel colder rather than warmer, anyway. I did want a Monster, though, and stopped at a filling station not far from our dark site and bought a monster of one.
|To use EQMOD, you plug a serial cable in in place of the hand control.
Once again, there had been zero doubt the weather would cooperate. We hadn’t had much in the way of rain in quite a while, and the universal forecast was “clear and cold.” Not crisp, though. Humidity was fairly high and appeared to be spiking up as the Sun set. Felt like the air would be just damp enough to make light pollution a problem for imaging. The Milky Way is almost always easily visible from our site once in climbs out of the Possum Swamp light dome in the east, but damp air propagates the glow from that light dome across much of the sky on a humid night.
Some folks complain about the weight of the Atlas GEM head. I’ll admit it ain’t a lightweight, but at about 50-pounds it is not insane, not even for a broken down old hillbilly like me, not when I’m careful. And as I’ve said before, at this price point you’ll have to accept “heavy” if you want “steady.” If you are willing to pay about five times what the Atlas commands, you can get “steady but light” with a mount like the wonderful Astro-Physics Mach 1, but Unk is way too stingy to consider that, given his minimalist needs.
Weren’t any hiccups during set up. I used a good compass to get the mount roughly aligned on Polaris’ position before that distant sun peeped out. Hooked up the computer. Mounted the guide camera. Installed a 1.25-inch diagonal and visual back on the C8. I’d do the go-to alignment with a 12mm crosshair eyepiece and then mount the camera. As is almost always the case, my C8, Celeste, was wearing the Celestron f/6.3 reducer-corrector I bought for her at the 1997 Texas Star Party (from the late, great Pocono Mountain Optics). Done, I kicked back, drank about half the Monster, and waited for dark.
|Serial-USB converter and EQDIR module.
How does this CdC/EQMOD combo talk to the Atlas? Over a standard serial cable connected between the PC’s serial port and the hand control port on the mount. There are a couple of gotchas, here, though. First off, no modern laptops or netbooks (or even desktops) that I know of have serial ports. That means you must provide one, usually via a USB – serial converter cable. Do yourself a favor and get a Keyspan, since they are known to work reliably with EQMOD. That’s not all you need, however. A PC speaks RS-232, but the Atlas only understands TTL. That means you must have a level converter module, an “EQDIR.”
The EQDIR, a little widget that translates between data formats, can be plugged in at either the computer or telescope end of the serial cable. I usually place it at the computer end; I don’t like the EQDIR sticking out of the mount’s DB-9 socket. That’s just asking for me to bump into it and either break it off or unplug it.
Where do you get an EQDIR? There are several sources, but here in the U.S. of A. most people buy from Shoestring Astronomy. Who has another product that’s even easier to use, the “USB2EQ6,” which incorporates a USB converter, an EQDIR, and a serial cable. Plug one end into a USB port on the computer and the other end into the DB-9 hand control port on the mount and you are ready to roll.
The mount’s cabled to the computer and the planetarium is running and connected to EQMOD. What happens next? When the EQMOD window opens, click the tool icon on its top right to expand it to reveal the set up display. There are quite a few settings to make including alignment method, gamepad options, and auto guiding parameters; the EQMOD docs explain exactly what must be done and how. Most importantly, enter the observing site’s latitude and longitude and save it to the hard drive. It is critically important that this lat/lon be exactly the same as what is in the planetarium program. Once EQMOD’s set up is done, it’s polar alignment time.
Since I usually only take two to three minute subframes, about the limit of what my site will stand before sky fog from light pollution becomes too bad, a decent alignment with the polar scope is all I need. I’ve always liked the Atlas’ polar borescope with its nice, wide apparent field of view. Too bad it’s tough to figure out how the R.A. axis of the mount should be rotated to put the little circle where Polaris goes in the right spot. Used to be tough, anyway. Thanks to Chris Shillito and the other gurus continuously developing EQMOD, borescope polar alignment is now a breeze.
How does it work? When Polaris is visible, unscrew the dome-shaped cover on the rear end of the Atlas RA assembly to reveal the borescope eyepiece and also remove the plastic plug from the forward end. At this time, the mount should be in normal “home” position, with the counterweight shaft down and the declination at 90, so the tube of the telescope is parallel to the RA axis of the mount.
|EQ-6 polar scope reticle.
Ain’t got a wireless gamepad? Get one. There are slew buttons on the EQMOD display, but it’s a pain to move the scope with them, especially when you are trying to center alignment stars. The good news is that EQMOD will work with almost any wireless PC game pad, and can even be made to use Wii or Playstation or Xbox controllers. Me? I found a perfectly good wireless pad/joystick in the dadgum Wal-Mart for 10 dollars.
When the polar scope’s view is clear, set the Polaris circle on the reticle to starting position. This position is selectable, but I find “6 o’clock” easiest to use. Center the North Star in the crosshair of the reticle with the mount altitude and azimuth adjusters, and then crank up in altitude until the star is on the big circle (not in the little circle) on the reticle. When it is there, use the gamepad to move the scope in R.A. to place the small circle around Polaris. Push the Set Polar Home button, the one with the plus sign and house icon on it, to record this starting position for future use.
Just about done. Mash the Align Polar Scope button (arrow and yellow star), and the mount will move in right ascension until the Polaris circle is at the proper angle for polar alignment. If you are using a telescope with a tube much longer than that of an SCT, make sure this movement will not result in the tube ramming a tripod leg. It that is a possibility, remove the OTA (and counterweights, natch) before polar aligning. Once the mount stops slewing in R.A., just use the altitude and azimuth adjusters to put Polaris back in the little circle, push the Park button to send Atlas back to Home Position, re-enable mount limits, and you are done.
|EQMOD polar alignment window.
Did all that in about two minutes, unparked the mount again, and was ready to get started with go-to alignment. EQMOD’s alignment method is one of the things that make it different. Different but good. Instead of picking stars from the SynScan’s too-small display window, you click on them on a planetarium program’s screen (I like to use Cartes’ all-sky display), center them up in a crosshair eyepiece with the gamepad, and push the “sync” button on the astro-program.
If that sounds too different for you, EQMOD also has a more “traditional” dialog based alignment system where you click “yes” on a window to accept stars. To enable the dialog system, select “Dialog Based” instead of “Append on Sync” in the Alignment/Sync section of the driver setup display. I used to prefer “Dialog,” since I could accept stars at the telescope with the gamepad, but I changed my mind when I realized I’d have to go back to the computer to select the next star, anyway, and that it was quicker to just to click Cartes’ sync button than to fool with another window. You can assign “sync” to a gamepad button, but I’ve never felt moved to do that.
Which stars do you sync on? I find making a huge, sky-encompassing triangle with three stars works very well. I usually pick a star in the northeast, one in the northwest, and a final one in the southeast. I try to keep them close but not on the horizon, maybe 10 – 15 degrees high. I have never had a problem with go-to accuracy when I have done this, with every object winding up somewhere in the field of a medium power eyepiece.
|Atlas and Celeste ready to go.
Other than the “new” (to me) polar alignment utility, EQMOD worked just as I remembered. Aligned on three stars, clicked to go-to Vega for focusing, and everything just worked. Vega was centered in a 15mm eyepiece when EQMOD said “Slew complete!” There are quite a few new features, and I refer you to the docs linked above for a complete rundown on them, but the main thing I noticed was that EQMOD now talks. Like NexRemote, it announces “Slewing to target” when you start a go-to, “Slew complete” when you get there, and many other things. As with NR, I find this both cool and useful. I do not like looking at the PC screen any more than I have to.
Mount aligned, next thing next was getting the guide scope focused. After the alignment, I’d plugged in the guide camera cables, brought up PHD Guiding, set exposure to 1-second, and begun looping frames. Vega was a big, fat blob at first, but screwing out the objective end of the guide scope to focus made it appropriately small. I was happy to see that as I approached focus many dimmer stars appeared. The StarShoot is more than sensitive enough. None of the three imaging fields I visited on this night lacked candidate stars. Focused, I snugged-up a knurled ring behind the little scope’s objective cell to lock focus down.
I know some people don’t use a PC with a DSLR, but I much prefer running the camera with a computer rather than setting exposures with a handbox and storing images on a Compact Flash card. Nebulosity from Craig Stark, the same talented dude who wrote PHD, is great. It delivers a big focus display, stores your images as .fits files on the hard drive, and allows you to set exposures and exposure sequences with drop downs and menu buttons. Nebulosity deserves a blog entry all its own, but for now I will just say that it is so nice to focus easily, set up a sequence of exposures, tell Nebulosity to start work, and walk away.
I told Neb to start exposing, waited for the first frame to be displayed, and when it did and I saw its stars were nice and round, I walked over to George’s set up to see what he was looking at, letting scope and computer do their thing on their own.
And so it went for the balance of the evening. After M13, it was the Dumbbell Nebula, M27, and finally, the good, old Ring, M57. Since Nebulosity takes and applies dark frames as well as light frames, twenty minutes of exposure takes something close to an hour from start to finish. I knew that, but when I finished with M57 I could still hardly believe it was getting on to 11 p.m. I also couldn’t believe I wasn’t cold. My heavy coat helped, but mainly I’d been so busy that I forgot to be cold.
Since I wanted to give EQMOD’s go-to accuracy a trial, slewing from horizon to horizon, I decided that would be a good way to end the evening. Stowing the camera and guide camera would put me a little ahead of the game when it was time to pack up, too. Off came the camera and prime focus adapter, on went the 1.25-inch diagonal, and out came my beloved Orion Expanse eyepieces. Maybe I should have brought the Ethoses and the Denkmeier Powerswitch diagonal with me, but this was an imaging run, and I wanted to cut down a little on the gear overhead.
To cut to the chase, EQMOD was impressive. If a go-to system has problems, accuracy will usually fall off somewhere: at the zenith, in the south, on the horizon. Obviously EQMOD did not have any problems, because every single object I looked at was somewhere in the field of the 9mm Expanse eyepiece. I didn’t leave it at the above four targets, either; I went all over the sky, trying to get EQMOD to put something out of the field. Nope. In my opinion, its accuracy is fully the equal of Celestron’s NexStar firmware, which is acknowledged to be the best in the business.
So Unk didn’t make any mistakes or do anything silly? What do you think? It wouldn’t be an Unk Rod night if there weren’t any weirdness. I was set up on the opposite end of the field from George. I did that so the computer’s and cameras’ red LEDs wouldn’t disturb his visual observing. Toward the end of the evening, he hollered, “I’ve got the Veil!” I swear I thought he said “I’ve fallen and I can’t get up!” I came at a run, needlessly disturbing George’s contemplation of his favorite supernova remnant. Oh, and I spent half an hour searching for the C8’s rear cell cap when I was packing up. Couldn’t find it anywhere despite much scanning of the ground with a flashlight. Naturally, next morning it was right where I put it in the accessory box.
Comments: Post a Comment