Sunday, September 27, 2015
The Nights Everything Goes Wrong Redux…
|Bertha's backyard M13|
Sometimes everything goes right under the stars. Not all the time, though. Not hardly. Not if you are an astrophotographer, or at least dabble in that black art as I’ve been doing for years. Even in the supposedly simple film days, there were just so many things that could go wrong. Today, when you have to deal with computers and goto mounts and cooled cameras instead of just a scope with a simple AC powered clock drive and a 35mm camera, there is tremendously more to go wrong.
The whole mess got started because of my need to check out my C11, Big Bertha, and her CGEM mount in advance of the fall star party season. I thought the C11 herself was good to go, since I’d done some fine tuning of her the previous week. Fine tuning because I knew the scope’s focuser needed attention. My last time out with Bertha months back, it had been noticeably harder to turn the focus knob than it used to be.
That can happen with a Celestron SCT when the screws holding the “collar” in place around the focuser shaft loosen and the collar becomes canted with respect to the shaft. The solution is to adjust all the screws till the collar is parallel to the shaft and focus knob. It only took a few minutes to sort this out and return the focus action to its normal smooth feel. I also had a quick look at the corrector’s cleanliness. It was not pristine but not in need of cleaning yet,.
The CGEM? That was an entirely different kettle of fish. I didn’t know it needed attention, but I also didn’t know it didn’t. I didn’t know much about it at all, frankly. In January of this year, I had finally had enough of the NexStar 11 GPS’s enormous fork, and had purchased a Celestron CGEM to replace it. I was able to test the mount a few times in the backyard, but only briefly thanks to terrible weather. I had hopes, though; I planned to resurrect Bertha for this year’s DSRSG Spring Scrimmage, to give her a good workout over three April nights in the wilds of northern Louisiana. Or so I hoped.
Alas, those hopes came to naught. First obstacle was that, for the second time in the last 30 years, I was summoned for jury duty. While I was released before I was due to depart for the Feliciana Retreat Center, that coincided with the arrival of wave after wave of thunderstorms. Since I was paid up for DSRSG, and, as with any star party, there could be no refunds, I drove to Louisiana anyway, but I packed the C8 and VX instead of the CGEM. Why wrestle with a big SCT when the weatherman said there was absolutely no chance whatsoever of me seeing anything?
The dire predictions of Weather.com and Scopenights were correct. I had an OK time at Feliciana, but the Edge 800 never came out of the 4Runner. In fact, the weather went from bad to worse in the short time I was onsite. I arrived on Thursday afternoon to rain, and left Friday afternoon to the accompaniment of booming thunder and flashing lightning.
And that was it for me even thinking about using the C11 for nearly six months. Both because of this summer’s even more horrible weather and because of non-weather-related factors. What little observing got done over those months was done exclusively with my simple Dobbie, Zelda.
|The new mount|
Rod ain’t no dummy—not usually—however, and I wasn’t fool enough to pack up a mostly unused mount and drive hundreds of miles hoping for the best. That’s how you incur the wrath of the astronomy gods. The CGEM needed to be tested as thoroughly as I could test it. Not just visually for a few minutes, but with a camera on the scope over the course of a reasonably long run.
As I wrote last week, I decided it wouldn’t be an overly onerous task to tear down the Edge 800 and VX, which were out in the backyard, and replace them with the C11/CGEM. That turned out to be not exactly true. Thanks to the still and sultry late September weather, by the time I finished getting the big mount on the tripod and the big OTA on the mount I was dripping with sweat. Stealing an occasional glance at the partly cloudy sky, I hoped I hadn’t wasted my time.
For once, wunderground.com said I hadn’t. A cold front was passing and would bring clear skies, if not on this night, then for several nights following. Since it is not a problem to leave the C11 setup out back for days on end, I figured I couldn’t lose. Ha!
Once the OTA was on the mount, I still had to rig up the DewBuster and the corrector heater. Mount the Rigel Quick Finder. Hook up the batteries. Plug in the hand control. Get the camera on the rear cell (via a make-do prime focus adapter as I mentioned last time; I couldn’t find my normal one and used an old OAG instead). Finally, since the camera I would be using, my “backup” body, an old Canon 400D, needed a Shoestring shutter interface box to do longer exposures, I had to hunt that up and hook it to the PC.
Standing there ogling Bertha after I finished, I had to admit she looked mighty fine sitting in the fading late summer light. Of course, looks mean nothing when it comes to scopes. We’d see how this new incarnation of my old friend performed.
Once dark, which is finally beginning to arrive a little earlier, came, I got to work, which was smooth sailing at first. I executed a 2+4 goto alignment, fired up the PC and started TheSky. That’s when my problems began. TheSky 6 Professional resolutely refused to talk to the CGEM, “There doesn’t appear to be a Celestron telescope connected.” I was flabbergasted. TheSky has simply never failed me. Never. I tried everything. Moved the serial-USB adapter to another USB port on the hub. Restarted TheSky multiple times. Rebooted the PC multiple times. Checked Device Manager in the PC’s Control Panel, which claimed I had a perfectly good Com Port 3. Nothing worked.
Astronomical twilight had now well and truly arrived. I was wasting time, so I reluctantly decided I’d forget TheSky for now; I’d figure it out by the light of day. I sent the scope to M13 via the hand control, fired up Nebulosity 3, and connected to the Canon. Or tried to. Nebulosity said there was no Canon camera that it could find.
What the heck was going on? Puzzled, I idly looked over at the USB hub. Something was different there. Its red LED was not illuminated. Could that be it? Could the freaking USB hub have gone bad? That didn’t seem likely. I’ve never heard of one failing…but there are active electronics in one, and it was years old so… I unplugged it from the USB port and plugged it into another one. Still no red light.
I ran inside, grabbed another hub, and connected it to a USB port. Its LED illuminated immediately. Plugged the USB-serial cable into it and tried TheSky. Still no dice. Went into control panel and reset the driver for the USB-serial adapter and suddenly everything was fine. Whew! Plugged up the Canon to the new hub and Nebulosity detected it immediately. My problems were over. That’s what I thought, anyway.
OK…I put Nebulosity 3 in frame and focus mode and got the cluster looking as sharp as I could by eye, twitching the C11’s now blessedly smooth focus knob. I then picked out a non-saturated field star, clicked on it, and switched to fine focus mode, which zooms in on the star and allows you to dial in focus precisely. I began focusing and was almost there when the star drifted out of the small box it was situated in. What the—? That was new. That had never happened before. I went back to frame and focus mode, clicked on the star again, Nebulosity zoomed in on it again, and away it drifted once again before I could finish focusing. What now? Was the CGEM down for the count?
I checked everything. RA and declination locks were firmly locked. Mount was definitely in normal sidereal tracking mode. Everything seemed OK. So why wasn’t it tracking? I didn’t know what else to do, so I reset the hand controller to factory values, reentered my site/date/time data and did a new goto alignment. Got M13 back in the field using TheSky—at least that was working now. Started Nebulosity, went back to fine focus mode, and watched that darned star slowly drift off into never-never land.
I was well and truly stumped, but luckily, maybe, this wasn’t exactly the first time I've been at a loss under the stars. At least I had the sense to STOP now, not do anything else, and just THINK. What causes stars to drift other than problems with the mount? Well, poor polar alignment. But I had done an Allstar polar alignment with the hand control, just like I always do and… Wait one freaking minute. What AllStar polar alignment? I hadn’t done a polar alignment following the goto alignment and that was why the star kept drifting no matter what I did. All I’d done was sight Polaris through the CGEM’s hollow polar bore. Hardly good enough when you are imaging at nearly 1800mm.
Again, so many things can go wrong when you're doing astrophotography—computers, computer programs, cables, hand controls, batteries, cameras—that it’s a wonder something doesn’t go wrong every blasted time. You just have to accept the fact that you are going to have occasional disastrous nights no matter how experienced you are. Yeah, I had egg on my face, but I hoped that meant that I was due some good nights over the coming months.
When I finally sent Murphy and his pal Finagle packing, I began grabbing images of M13. This was special, since this was—get this—the first time I’d taken prime focus (non-video) deep sky images with the C11 I had owned for over a dozen years. In her former incarnation, it just wasn’t practical. The alt-az fork was fine for video exposures but not for DSLRing or CCDing. Yes, I had a good wedge for the scope, but mounting Bertha on it was a two-person job, easy, so I rarely did that.
So, what turned out to be the deal with the C11 and CGEM once the images started hitting my monitor? Nearly 1800mm (with the f/6.3 reducer corrector on Bertha’s rear port) is a lot of focal length to deal with in my book, and the CGEM is hardly a top of the line mount. I like it just fine, but there’s no use pretending it’s a Bisque or an A-P. Nevertheless, I was pleased with what I was seeing on the laptop, especially considering the fact that I had to go unguided.
I don’t have a guide scope mount for Bertha, and the guide camera I have, an old Orion StarShoot, is not sensitive enough to use with an off-axis guider. That didn’t mean I couldn’t take pictures, though. I found I could go 30-seconds without guiding and keep a respectable number of frames. Backing off to 15 – 20 seconds meant almost all were perfect, and, frankly, all could have been used in a stack if I weren’t being picky. 15 – 20 seconds is perfectly fine for me at the moment given my interest in short-sub imaging, but I might think about a better guide cam or at least a guide scope mount for Bertha eventually.
Frankly, I was rather impressed by the images the C11 delivered as compared to a C8. More aperture will not give you brighter nebulae or galaxies. Extended objects just get bigger in larger aperture scopes (assuming the focal ratio stays the same) not brighter. Stars are another matter. The C11 pulls in more, and combining that with the larger image scale of its longer focal length made M13 look nice indeed. Star colors were good and the core looked real sweet.
The next morning, I found it easier, I thought, to process the cluster without burning out the core than it is with a C8's images. Since star clusters, open and globular, are prime targets for my backyard imaging, I think the C11 will be preferable for that. Might make it easier to tease some detail out of planetary nebulae, too. Of course, there is the fly in that ointment: I have to convince myself to set the big thing up.
I didn’t stop with M13. I’d sweated too much blood on this night to leave it at that despite the now rather late (for me) hour. From M13, I went to M92, M15, M56, NGC 6888, and a few others. All were easy enough to capture, and all were easy enough to process. The old 400D acquitted itself well. While I would have been tempted to go to an ISO higher than the camera’s maximum of 1600 if that had been available, in truth it would have been a mistake in the light pollution and with a Moon in the sky. As it was, processing wasn’t a pain, but I still had to deal with some gradients.
How about the mount? I have nothing whatsoever to complain about. While it is an “inexpensive” GEM, it did bring home the bacon. I will be interested to see how easy it is to guide. I don’t expect perfection, of course. The C11 is a heavy enough and even reduced has enough focal length that it really cries out for a mount two or three steps above a CGEM. A Losmandy Titan or a Bisque MyT or an A-P Mach 1. The chance of me acquiring any of those fine machines seems slim, however, and why should I worry about it if the CGEM can do what I want it to do? For me that is casual imaging of the sort I did on this evening and deep cruising with the Mallincams, and it’s already obvious the CGEM is more than capable of both things.
There is one area where the CGEM bows to no mount: goto accuracy. Do a good 2+4 alignment, and the CGEM will put anything from one side of the sky to the other in an eyepiece at 150x – 200x. You might get your high-priced-spread of a GEM mount to do better, but not without doing a 100 point T-point run, and you can do T-point with the CGEM too. Frankly, I am satisfied; as I hoped, the CGEM is an improvement in both portability and performance over the fork (except for goto accuracy; the fork was outstanding there, too).
What’s next? When the Moon is New again, I will be at a star party, the Peach State Star Gaze, with Bertha. I may actually try to get out sooner than that for some more short-subbing once Luna begins to wane, though. That is assuming the weather gods and my moods allow, which is always a tossup, natch. Stay tuned.
Wow,the main thing that seems to always be in your favor is you are a man who knows when to stop and regroup.To solve many problems I have come across on my job (no astrophotography here)the answer is take a break ,walk away and get back with a clearer head....Good reading as always on a Sunday morning,thanks.
Totally reflects my last dark sky imaging session when firstly the DSI II suddenly stopped working. Unplugged replugged and restarted the comp. Worked for a bit then Envisage started behaving eratically...exposure countdown was jumping all over the place. Rebooted the comp and just when I though everything was peachy, the comp decides to do an update while I was imaging. That was when I 'pulled the accursed switch' and swith to visual.....Post a Comment