After getting mostly unpacked and having several clear days that had cloudy nights, I finally set my telescope up this afternoon. My backyard faces south, which is great, since there are more deep sky objects (and planets!) southward. I have about a 100-degree-wide swath of open sky between my neighbor's large evergreen tree and my lemon tree, which only goes down to 60 degree of altitude over their backyard, but goes as low as 37 degrees above my back fence. If I am patient and image over many nights, I should still be able to do some good imaging! I've seen some phenomenal images from light-polluted skies, and I'm at Bortle 7. Many of those images are narrowband, which takes a thin slice of the spectrum where there is little light pollution, but some of them are wideband using light pollution filters, or multi-bandpass filters like the Optolong-L. It's certainly not an ideal setup, but I can still do some good with it, and best of all -- I can set it up, and go to sleep! No one can see into my backyard unless they walk all the way up my neighbor's driveway and peak over the locked fence.
Mount: Celestron Advanced VX
Telescope: Takahashi FSQ-106N
Camera: ZWO ASI294MC
Filter wheel: Starlight Xpress, with 2-inch Astronomik LRGB Type 2c filters
Guide scope: Orion 50mm
Guide camera: QHY5
The rest of the afternoon, I processed photos and double-checked software on my tablet. I saw a Celestron ad in Sky & Telescope that said that their new Planewave application for controlling Celestron mounts now included several serial-based models, and not just their USB-controlled mounts! Any mount with a NexStar+ hand controller can now be controlled by their PWI software. This is really exciting because I can save alignment models and re-load them instead of relying on hibernation to work and hoping there's not a power cut from me doing something stupid. It also includes some more intelligence than the hand controller alone; for example, after you do the polar alignment, it automatically updates the star alignments you already made, so you don't have to re-align after a polar alignment!
Once twilight began, I went outside to get my tablet hooked up and get everything checked. I decided to attach my Astronomik CLS filter, which is a light pollution filter that cuts out the waveband where high-pressure sodium lies. I forgot that 2-inch filters are M48 and not M42/T-thread, however, so I couldn't attach it directly to the camera. So I ran inside and got my filter wheel, swapped the luminance filter for the CLS filter, and put the filter wheel on. I've been meaning to try using the CLS filter for luminance on my monochrome ZWO ASI1600MM Pro anyway, and now I can swap them in and out without even having to change focus. Luckily, my Starlight Xpress filter wheel is super easy to swap filters in and out of -- it has five thumbscrews on the front, and then the filter wheel carousel just slides right out, no tools needed.
A couple of brighter stars had appeared, so I slewed to Deneb to focus so that I could do a star alignment. (The PWI software lets you do a "quick align," where you just say you're at the home index position and it bases your alignment model on that). After auto-stretching the histogram in SharpCap and changing the exposure time to 1s, I could see a defocused Deneb in the frame (after I put the star in my red dot sight). However, I ran into an immediate problem: the manual controls for my Robofocus weren't working, even though the pilot light was on. I tried connecting it to my computer via serial-to-USB, but the Robofocus app wasn't detecting it. Finally, I powered down the Robofocuser and just focused manually (the Robofocuser disengages a magnetic lock when it's shut off so that you can do this without breaking your focuser). I'll have to keep investigating that.
I got focused using my Bahtinov mask, and then did an alignment with just some eastern stars, since my western view is largely blocked by my lemon tree, except up near the meridian. After two stars and Saturn, the PWI software prompted me to do an All-Star Polar Alignment, which gave me a few options for stars near the horizon & meridian, and I chose Nunki, which was easily visible. The mount slewed to where Nunki should be if I was perfectly polar aligned, and then I moved the mount there, and hit Done. Easy! The only hard part was using the mount controls via keyboard in the PWI app while also seeing my camera's live feed. The slew controls have to be on top, but unfortunately the window their in is not separate from the main PWI window -- when I select that window, the whole PWI app comes back up on the screen, blocking SharpCap. So I had to make each app half-screen in order to see my camera feed and have the PWI app open so I could actually slew the mount. Very annoying! Anyway, I'm glad Celestron has that All-Star Polar Alignment feature, since the roof over my porch, my neighbor's garage, and my plum tree block the north star.
With that complete, it was time to do some testing. I wanted to see if the auto-meridian flip would work (and make sure cables wouldn't get snagged). So I found a star that was about to cross the meridian, got the settings set, and gave it a try. Plate solving was being really slow, however. By the time I changed some settings, the star would have already crossed, so when I told the mount to slew to that target so I could test the flip, it would already flip just on the slew. This happened about three times before I gave up and decided just to have it stop imaging about a half hour after the target transitted (my mount can go 20 degrees past the meridian). After I calibrated guiding, my original target for the evening, M27 Dumbbell Nebula, was only about an hour away from going behind the tree, so I decided to pick a different target and settled on the Eastern Veil Nebula. Slewing to it put it mostly where I wanted it inside the frame, so I next started testing what exposure time I could get that night. 30s had nice round stars, then 60s, then 120s. With the CLS filter, the histogram peak was still pretty far toward the left, and since this was an experiment night anyway, I went ahead and just left it at 120s. I'll see how far I can push it with guiding on future nights. Guiding wasn't looking all that great, but a 530mm focal length on the telescope is pretty forgiving.
I ticked the box in Equipment Profile to park the mount upon sequence completion, set the number of frames to take, and went inside to get ready for bed. I was worried that the park command wouldn't work, but it at least should stop the mount from tracking. I also took comfort in knowing that even if the mount kept tracking, there was a safety stop in RA that would stop the gears if it was hit. After I got ready for bed, I went out and checked it one more time -- everything looked good.
While I was working outside, my neighbors behind me were on the other side of the fence sitting around a fire pit and singing. One person played guitar, and another played cello. It was a family choir; they even harmonized together. It was lovely being serenaded while I worked! I wanted to grab my cello and join! They sang songs like Space Oddity, The Boxer, and even the Foo Fighter's "Stranger Things Have Happened," along with some tunes with which I was unfamiliar. I did sing along to a few songs quietly, which was fun. (I also hoped that the smoke wouldn't fuzz out my images too much!)
I slept in and got up around 8 AM the next morning, and went outside to go check it. Sure enough, it was all the way over on one side -- the park command hadn't worked. And the gears were still spinning! I was very worried about this. I cut the power to the mount and logged back into my tablet to see what had happened. It was still trying to park it -- I think it didn't give PHD a command to stop guiding, and that was interfering with the ability for it to park. When I manually brought the mount back to home position, the dec axis column slid down a bit -- I had forgotten that when I was troubleshooting the issue with the frozen dec axis, some extra space had been created, and the dec column wasn't quite tightened down all the way (which would have re-frozen it), so when it was tipped past the meridian, it slides out a tiny bit. As it turns out, it's enough for the gears to disengage, which is why they were spinning freely when I got out there this morning. This meant they weren't actually turning against a load, so I most likely didn't actually break anything. Phew! I will just have to set SequenceGenerator Pro to do the meridian flip shortly past the meridian so that the column doesn't slip.
Still in my pajamas, I went ahead and started troubleshooting the parking issue. As it turns out, I didn't have a park location set, so I set that in the PWI app, which is what SGP commands to park. I tested it, and it worked! Then I created a dummy sequence to make sure it would work in a sequence and not just with me hitting the "park" button. I added two targets to the target list -- two stars in Ursa Major to save me some time in slewing. I set them just to slew and not also center since it was daytime anyway. I also disabled guiding so that it wouldn't wait for PHD to be ready. After some fiddling with settings, a beautiful thing occurred -- it slewed to the first star, took some 1-second exposures until I stop time that I set, then slewed to the second star, took a set number of exposures, and then parked itself in the home position! It continued tracking, however, so I'll have to work on getting it to stop tracking too. (If you tick the "park at end of sequence" button, you cannot also tick the "stop tracking at the end of sequence" button.) I might be able to get around this by having it disconnect equipment at the end of the sequence.
Things are starting to come together! Can't wait to start getting bunches of data to process.
Eastern Veil Nebula, single 120s frame
(click here for the final result!)
(click here for the final result!)
Next post: #203 - Sunday, September 1, 2019 - Handywoman Skills
Previous post: #201 - Saturday, August 3, 2019 - Final Members Night
Previous post: #201 - Saturday, August 3, 2019 - Final Members Night
Post a Comment