Friday, April 19, 2019

#182 - Monday, April 15, 2019 - Pre-Texas Star Party Checkout

That magical time of the year is fast, not Christmas...the Texas Star Party!  A solid week out in the middle-of-nowhere southwest Texas, near the small town of Fort Davis.  This will be my third year!  Each year, I pull out my gear to make sure I have all the parts and pieces I think I do and see what the state of everything is.

It's been nearly a year since I last pulled out my 11-inch Schmidt-Cassegrain and its Celestron CGE Pro mount.  I describe some of the issue in my series of posts last year about the Texas Star Party (starting with night 3's post), but I'll give you the rundown. 

It all started at the 2017 Hidden Hollow Star Party, in late September of that year.  Just a few months prior, I had roaring success with the CGE Pro at the Green Bank Star Party in mid-July, accomplishing 8 minutes of guiding at least, which for some isn't much, but for me is a lot!  (And by that I mean, I could take an 8-minute image and not get any star streaks from tracking/guiding errors).  At Hidden Hollow, however, I started having issues with guiding -- my guide plots were all over the place, and I couldn't take images longer than like 30 seconds of so without streaking.  This was terrible!  I finally figured out that the declination axis had some kind of jitter -- when I slewed slowly, I could literally see the stars bouncing back and forth.  The right ascension axis was still buttery smooth.  Fellow club member Jim and I popped open the casing and took a look, but nothing looked out of place.  I could, however, rock the dec axis back and forth by hand, which was not a good sign.  But it started getting cold as soon as I got home, so the mount stayed indoors all winter.

It didn't warm up enough that spring before the Texas Star Party for me to pull it out and tinker, so I brought it as it was down to TSP.  I figured out how to remove the cover while keeping the telescope loaded, and observed that the worm gear had some somewhat separated from the main dec axis cog wheel, which was causing all of the slop.  I tightened up the bolt that pushes the worm into the cog, but finding the exact right position for it was tough -- I didn't want to cause binding as well.  Some folks around me offered ideas, and I even talked to the Celestron people who were there, but unfortunately they didn't have any of their engineers in attendance.  They were flabbergasted to hear that the CGE Pro was having this problem, especially after it had been Hypertuned!

And finally here we are, a year later.  Time to see where things were at.

I got home somewhat late from work, and was halfway through the first episode of the last season of Game of Thrones when I looked at my watch and saw that it was already 8:20 PM!  So I paused the show and started pulling my gear together to take downstairs to the front yard to set up.  I just needed to see some stars so I could guide.  It was pretty clear that night, although chilly in the mid-40s.  But looking at the forecast, it would be my only opportunity before TSP most likely.

Once I put the cats away in the den so I could leave the door open, I picked up my CGE Pro mount head in its box -- I forgot just how much that thing weighed!  It's about 60 lbs!  And I have been slacking on the gym-going over the winter.  As I started to descend the stairs inside my apartment, my legs began to wobble, so I had to change tactics.  I put the box on the stair a few stairs above me, and then braced it on my legs to move it down one step at a time.  It was slow going, but much safer and easier.  (I almost fell down the stairs with it once).  All of my the rest of my gear felt light by comparison!  All told, I moved about 250 lbs of gear or so down the stairs.

"The Beast" loadout: box with the equatorial section, pier, cables, nuts, and bolts; C11 telescope; 80mm guidescope; mount head box; three counterweights; tripod; computer table; tackle box; cameras; battery; filter wheel; and some warm clothes.

It took me about an hour to set it up, which went pretty smoothly for not having done it in a while.  They only thing I couldn't find was the SCT-2-inch connector, which I ended up finding in my ZWO camera bag, where I had strategically left it previously to use with my C8 for planetary imaging.  I went ahead and moved it to the tackle box, which is where I expected it to be.  The tackle box is like my favorite thing; it's enormous and probably weighs about 30 lbs fully loaded at the moment, but it was everything I need: batteries, cables, adapters, extension tubes, parfocal rings, nuts, bolts, hex wrenches, screwdrivers, scissors, velcro, vice grip, pliers, cable ties, and more. 

After attaching the camera and filter wheel, I got it balanced, and realized I needed that third counterweight!  I could hear the tripod creaking as I moved things around.  I tightened the leg leveling bolts and the stabilizer a bit more.

"The Beast"

I haven't turned it on since last May :(

I was going to look visually through it first to see if the jitter was still there, but since the camera was already attached, I decided to go ahead and polar align it, align it, and see how the guiding would do in its current state.  I firmed up the worm gear pretty decently last year, but the data I took after that were relatively low in altitude, so the guiding may have been affected by the atmosphere.

One annoying thing about this mount is that you have to re-position the altitude adjustment screw for latitudes above 40 degrees and latitudes below 40 degrees.  When you get close to 40, however, you're really running out of screw at least a few degrees before that.  Plus, one of the bolts you need to remove to do the switch is stripped!  So I can't actually do it.  Fortunately, one of my friends at the Green Bank Star Quest in 2017 came up with a simple and ingenious fix -- give the screw a little extra length with a giant nut!

So simple!  And works so well!

I set the altitude marker near my latitude, checked that it was pointing mostly north, and then fired up SharpCap to do a proper polar alignment.  The Pro version of SharpCap has an excellent polar alignment tool, in addition to others, and it's only $15/year.  I got everything connected, and after finding focus, I started the procedure.  I could see numerous stars easily, but it was unable to plate solve the image!  I messed with gain, noise, and exposure settings, but was getting nothing.  Then I wondered if I was just so far off the pole that it was outside the plate-solving database area it had.  I looked through the Telrad - and yeah I was way off in altitude!  But I had set the altitude using the marker, hmm...oh wait, the nut adds like five extra degrees of height *smacks face*.  So I adjusted both axes until Polaris was near the center of the Telrad, and then tried SharpCap again.  Plate solve no problem!

Now, if you've been following my blog or have spoken to me before, you have heard me say how terrible the altitude adjustment system is on the CGE Pro (Celestron have a much better one on the CGX-L, I will note).  Basically, the gist of the problem is that when you turn the altitude knob, you are pushing against the entire weight of both the mount head and whatever telescope, counterweights, and other gear you have loaded.  For me, this means I'm trying to turn a knob against over 160 lbs!  Turning by hand is impossible, and I borrowed a belt wrench at last year's TSP, but that was also pretty difficult.  But, last year, I noticed that the hand knob had holes in the side all around it.  So after I got back, I went to Lowe's and bought two long rods that fit the holes perfectly.  Now I can get all kinds of torque, and it turns no problem!  I do have to take them out every quarter turn to shift to the next set of holes, but it's not too bad.

While I was polar aligning, I noticed that the stars seemed less in focus near the edges than the center.  This suggested I needed to collimate.  I decided to try what I've been meaning to try -- collimating with my camera!  I slewed over to Capella, defocused the star, messed with the exposure time to get a nice image, and then saw that my donut was, indeed, a little asymmetrical.

One of the cool things about collimating a Schmidt-Cassegrain is that you can literally point to one of the three adjustment screws and see which one you are pointing at in the image.  This makes it very easy to know which one to turn!  So I made the adjustments, and got it probably fairly close.

After that was all done, I aligned, which went pretty smoothly -- after polar aligning, now each star landed in the field-of-view of my camera, and then I just had to center it in the camera view.  I did two western stars and two eastern.  I did notice, however, that the alignment didn't seem to get better - even after the fourth star, they weren't landing much closer to the middle of the image.  Weird.

Next, I needed a quick imaging target -- I could have just dropped it anywhere to check on guiding, but I figured I may as well grab a few images while I was at it.  So I popped over to M13, but I stopped by nearby Alphecca first so I could focus the guide scope.  I had to add an extension tube to get my QHY5L-II to focus into my Celestron 80mm, but once that was added, Alphecca first appeared as an enormous circle on the bottom of the image, so I just had to jog the scope up a bit so that it would be centered in the guide scope for focusing.

Finally, with all that done, it was time to calibrate PHD for autoguiding.  I got it connected, and was just about to hit go tablet shut down!  Running both my ZWO ASI1600MM Pro and my QHY5L-II off of it were just too much for the battery while plugged into the 1.5A USB power on my Celestron Power Tank.  I really need to be on 2.4A to run cameras, but an even better option is to just power the USB hub.  (The ZWO's cooler runs on 12V power, but the camera itself can run on 5V USB power alone, which is handy for planetary imaging when sensor temperature matters less).  So I ran upstairs and grabbed my 2.4A smartphone battery and a micro USB cable to power the USB hub that everything was plugged into, got everything hooked up, rebooted the tablet, and was rolling again not too much later.

I calibrated PHD...and got a non-orthogonality warning!  It did look a little non-orthogonal, and there were a few bad points.

I accepted it anyway so I could see what it really did to the images.  I flipped over to Sequence Generator Pro and finally took my first image of the night, around 11:15 PM, of M13.  I took a 3-minute image to start, but I could already see some pretty bad streaks.

Cropped view of a streaky M13.

I tried re-calibrating, but it looked even worse.

And guiding looked bad.

So I finally took off the camera and filter wheel and threw an eyepiece on, which I should've just done in the first place to save me a bunch of time.  Sure enough, the problem I started seeing in 2017 was back, with a vengeance!  Slewing in dec at slow-ish speeds made the stars jiggle back and forth as they slewed, making little streaking lines to my eye.  I could hear it happening too -- it almost sounds like something is sticking or dragging.  It was worse pointing west than east, but it was still present looking east.  It's bad enough that I can probably work on it during the day and not need to see how the stars are affected because the sound is so obvious.  Maybe I'd be able to see the jitter looking at trees or something too from inside my living room.  I'm hoping to get a chance to take a look inside and tighten things up during the daytime before I have to leave.  

I tore down shortly after that, around midnight.  My fingers started to freeze because so many tasks require having ungloved fingers, like attaching cable ties, loosening thumbscrews, etc.  I hauled everything up the stairs as quietly as I could so as not to disturb my downstairs neighbor, but I'm pretty sure she hates me, haha.  For the mount head, I did the same thing going up as coming down: I used my legs to brace it and push it up one step at a time.  My knee had started to hurt from accidentally turning it out a bit when I lifted, so I ended up having to do bad-form lifts using more back than legs.  My back was sore for three days!  Whoops...

Can't wait for the Texas Star Party!  Hopefully I can get things to work!  I think I've got a solution for the dec axis sticking/freezing on my Celestron AVX as well, but haven't had a chance to finish implementing it yet.  I'll write a post on that whole process when it's done.

Wednesday, April 10, 2019

#181 - Tuesday, April 2, 2019 - Fuzzy Colors

Lucky me, another night out this week!  Looking at the forecast the other night, I didn't think it was going to happen, so I put my gear away, but then the weather cleared up for tonight!  The atmosphere wasn't promised to be great, but I don't need great seeing for the color data I need to take on M82, the Cigar Galaxy.  Then I'll just need one more night to get the hydrogen alpha so I can make a killer image, hopefully!  On top of this being a clear night, it's downright balmy at 44 degrees F!

I got out to the observatory around 8:20 PM, turned on the heat in the warm room, and got the dome set up.  Got my guide camera and main imaging camera plugged in, attached my super-awesome cable bundle, connected the cables to my computer and main power, and booted everything up.  It was still dusk, so I decided to see where the mount was at with polar alignment.

It was off by about an arcminute, which is fine but could be better, especially since this is a permanently-mounted system.  So I polar aligned using SharpCap, and since it was still too bright out to start imaging, I decided to give PHD's drift alignment a try.

Post-polar alignment

It wasn't very difficult.  First, it has you slew to a spot near the celestial equator and the meridian.  You don't even need to find a nearby star in your mount's star catalog -- PHD conveniently fills in the coordinates for you, and sends a command to the mount to go there.  Easy peasy!  Then you just watch the dec trendline for long enough to have enough points to see the trend (and not the atmosphere), adjust the azimuth a little one way and see where the line goes, and try to get it flat.  It even has a little space to put notes so you can remember which knob makes the trendline move which way.  I was getting close on azimuth when the guide star started getting lost in the noise -- there was a bank of clouds!!  So rude!  So I waited about 10 minutes, and luckily it passed, and I got back to it.

I couldn't get it perfectly flat, but it was close, and the adjustments I was making were tiny.  So I switched then to the altitude adjustment, which has you slew to a spot near the celestial equator and either the eastern or western horizon.  It had coordinates programmed in for the western horizon, but the main observatory building blocks the way, so I flipped it to east (switched the meridian offset degrees from -65 to 65) and then started the drift process.  It immediately shot up!  That was weird, I thought I was very close to polar aligned.  I made a small adjustment on the altitude knob to see which way I needed to go, and it came back down immediately.  Through some trial and error, I figured out that this was a very touchy adjustment, and I only needed to make very small adjustments on the knob, no matter how bad the guide graph looked.  I eventually got the line pretty level.  The whole thing probably took about 10 minutes if you don't count the clouds rolling in.

Once that was done, I slewed to Dubhe to see if my alignment model was still any good after the adjustments -- and it was quite close to center!

Good enough for me...

Next, I slewed southish to some random star I clicked on in the Celestron PWI app so I could calibrate PHD for autoguiding.  PHD says that calibrations are best done at declinations lower than 20 degrees.  That went swimmingly, and then I slewed to M82, and took a 10s exposure to check its position (faster than doing a plate solve for something as bright as M82).  It was slightly off-center, but close enough for me!

So I flipped over to Sequence Generator Pro from SharpCap and configured the sequence.  Another cloud bank had rolled through, so it was 9:45.  I didn't want to be out later than midnight, so I divvied up the red, green, and blue exposures to fill that time.  I was going to do 5-minute exposures, which would mean I could do 9 subframes per channel, but with the cloudlets floating through, I decided to drop to 3 minutes in case I needed to toss any out.  I had enough time for 15 per channel, but then remembered how abysmally slow SGP is at downloading frames, so I dropped to 14 per channel.  I was about to hit the "go" button when PHD started yelling at me -- the one and only cloud in the sky was right over M82!  Jerk!  So I waited a couple minutes for it to move along, and then hit "go."  The filter wheel rotated to the red filter (a very gleeful moment), I checked the slit position on the dome, and then waited a few minutes for the image to come in.  Guiding looked okay, but not great.

I changed integration times to 6 seconds per frame since the atmosphere was kind of mushy.  But the stars looked fairly close to circular, so I called it good and went inside to hang out.  It wasn't particularly cold outside, although I did have on my Cuddl Dud pants, jeans, under armor shirt, sherpa-fleece-lined sweater, winter coat, and knit hat, but I didn't need my gloves or my fleece-lined hat.

At 11 PM, I went back out to do the meridian flip, and it ended up a little high in the frame, so I decided to use AstroTortilla to plate solve and move the scope.  It was successful in solving the image, but it say on "Re-centering..." for like two minutes, and I didn't hear the scope move.  It was definitely talking to the scope though since it was showing current coordinates in comparison to the image-based coordinates.  So I gave up and slewed it myself.  I was about to continue acquiring frames when I went and checked the last few frames, and it looked out of focus a little bit!  Then I remembered that I forgot to check I slewed to a nearby brightish star, put the Bahtinov mask on, and checked, and sure enough, it was a little out of focus!  There goes half the night...darn.  So I focused, centered the star and added it to the point model to correct it a bit, and then slewed back to M82, which was still a bit off-center but close enough.  Turned guiding back on, hit Go, and went back inside to warm up.  I didn't have my thermometer running, but it felt like it was dipping into the 30s.  That little exercise wasted about 15 minutes.

The transparency was not excellent, and this was further evidenced by a low-ish-flying airplane that passed by on my way back into the warm room -- I could see the light path of its headlights for several degrees in front of it!  And my images do look a bit blurred.  But again, color data is quite relaxed in its requirements.  So we shall see!  Glad I'm not doing hydrogen alpha tonight.

I went out at midnight to check on things, and things were still rolling, but the last blue frame I looked at looked kind of terrible.  Fuzzed out and bloated!  And since it was midnight, it was time to pack it in.  I'll process the data anyway and see how things look, since my luminance frames should be good, although I'll only have half the blue frames I had planned thanks to the delay.  We'll see how it goes!

Here's a single 3-minute subframe in the red channel!  It looks ugly now, but soon it will be a beautiful butterfly...

Monday, April 1, 2019

#180 - Sunday, March 31, 2019 - In like a lion, out like a lamb

The sky was thick with clouds and the breeze was strong, but the forecasts said it would clear between 9 and 10 PM -- and I'm a believer!  So I packed up my gear in the car and drove out to the observatory.  I had a few new toys to try out -- a new electronic filter wheel (Starlight Xpress 5-position 2-inch, USB-controlled), and some cable management!

Just after installing the filters.
The blue-looking one is the red filter, the pink one is the green, and the yellow one is the blue.  (They're rejection filters).  Clear one is luminance (blocks UV and IR)

I spent Sunday afternoon taking the advice of the good folks on The Astro Imaging Channel and wrapping my cables in some of the 50 feet of flexible cable sock I bought.  I had previously put off doing this because I change configurations so often -- this camera on that telescope, with or without dew heaters, multiple rigs at once while at star parties, etc -- but cables are cheap, so I just bought a bunch of duplicates.  The cable sock I bought is self-closing, so instead of feeding a cable through, I wrap the sock around the cables, so it's pretty easy to add or remove cables, and it's easy to have them pop out before the end of the sock if I need to run cables farther along.  The cable configuration I built for my astro club's memorial scope includes: a USB 3.0 cable for my ZWO camera, a USB 2.0 cable for my new filter wheel, and the power cable (with a couple of extensions) for my ZWO camera.  My guide camera gets plugged into my ZWO camera (which has two USB ports on it), and since I have my USB hub attached to the pier, I just have the Celestron mount connection USB cable separate from the bundle.  My USB 3.0 hub is velcro'd to the pier, and then a USB 3.0 cable runs to my tablet.  Now I only have one thing hanging off the scope!  I suppose I could also plug the filter wheel into the camera, since it only draws 100 mA max (part of the reason I picked that particular filter wheel -- no external power, and very low consumption!).

I also made cable configurations for using my DSLR (DSLR USB cable, DSLR power, guide camera, and Celestron serial cable), and then one for either of my Celestron configurations with my ZWO (USB 3.0 cable, Celestron serial cable, filter wheel USB 2.0 cable, and two dew heater straps), and then one specifically for the Texas Star Party, where I'll be using a SBIG ST-8300M I'm borrowing with my manual filter wheel on my 11-inch Schmidt-Cassegrain (USB 2.0 cable for SBIG, SBIG power cable, guide camera cable, my other two dew heaters, and the Celestron serial cable).  Yeah cable management!  No more snagging on stuff by accident, and fewer things to move around and mess up guiding.

So I got out to the observatory around 8:20 PM, and the clouds were still thick, but I went ahead and set up.  First I set up a timelapse, since watching the clouds dissipate is pretty cool.  (Sorry I haven't posted last week's timelapse video yet -- I'm having some file naming issues, I think I'm just going to write my own script to do it!).  Then I opened up the dome, plugged in my cameras, and connected everything to my cable bundle.  It's beautiful!

Still got a bit of a power cable mess, but that part doesn't move, so I'm less concerned...

Buuuuuut the clouds were thick.  So I decided to take some flats. I slewed the scope down to a level I could reach, attached a white t-shirt using a stretchy headband to the objective, set my Celestron PowerTank on the slit window ledge thing, and turned on the large white light.  I then remembered that I probably wasn't quite in focus with the new filter wheel, but I figured I'd take them anyway.  Once that was done, it was still super cloudy, but there were a couple of tiny suckerholes through which I could see Castor and Pollux.  So I slewed up there, threw on the Bahtinov mask, and focused as best I could with a fuzzy diffraction pattern image (see more about that here).

Spikes are still centered!  Bahtinov masks are great.

While slewing, it sounded like the motors were having a bit of a hard time, so I decided to go ahead and change the balance on the mount, since I'm the main person using it (and anyone using it with just an eyepiece won't miss being balanced as much as I will!).  It was pretty decently out of balance in both RA and dec, so I adjusted that, and then went and sat inside to wait for the clouds to clear.  I decided I'd wait till 11 PM.

The Astro Imaging Channel broadcast started a little before I came back inside, so I hopped on from my cell phone since the cell signal is better than our wifi here.  I haven't gotten that to work in the past, so that was fun!  I stayed on after to chat with the another panelists, from whom I always get great info.

Around 10:30, I poked my head out, and it had cleared out pretty significantly!  And the stars looked steady, plus I could see a lot of them, so the seeing and transparency were probably pretty decent.

Worry not, I turned off the lights before starting to image.

So I scooted out to the dome to get rolling.  I loaded my previous alignment model that I'd saved to the computer, slewed to Arcturus to check focus, and it was nearly in the crosshairs!  Goto on the Celestron CGX-L we have out in the memorial dome is pretty excellent.  I calibrated guiding there, and then slewed to M82, the Cigar Galaxy, which was my chosen target.  I thought about taking more hydrogen alpha imagery, but I wanted to use my new filter wheel!  I tested a 3-minute luminance frame and the stars looked solid, and then I tested a 5-minute frame and it still looked good!  And the guide plot looked great.  Now, imaging that close to the north celestial pole makes an easy job of guiding because the RA axis is moving very little, but maybe my balancing also helped.  I'll have to see when I image somewhere farther from the pole.

Flipping across the meridian, which is usually a scary process because of all my cables, was quite painless this time around.  M82 ended up a tad high in the frame though, and Sequence Generator Pro is soooooooo slow at downloading even the frame & focus frames that it's hard to get something re-centered.  But I didn't want to swap back over to the faster SharpCap because I didn't want to wait for it to re-cool, and getting AstroTortilla to grab the image when it's connected to SGP is dicey, and I haven't figured out how to plate solve and center in SGP yet, so I just did it myself.

All too soon, midnight rolled around, and I did have to work in the morning, so I packed up and headed home.  I got through 17x300s subframes on the luminance channel (so didn't really use the automation on the filter wheel, boo), so I'll have to collect the RGB and H-alpha next time I'm out.  Here's a single screen-stretched luminance frame:

Single subframe (300s)
Date: 31 March 2019
Object: M82 Cigar Galaxy
Attempt: 3
Camera: ZWO ASI1600MM Pro
Telescope: Meade 127mm ED apo f/9 (club's)
Accessories: Starlight Xpress 2-inch filter wheel, Astronomik Type 2c LRGB 2-inch filters
Mount: Celestron CGX-L
Guide scope: Celestron 102mm
Guide camera: QHY5

A successful night!  And somewhat representative of the month of March as well -- in like a lion, out like a lamb.

Here's the timelapse video: