Thursday, March 28, 2019

#179 - Tuesday, March 26, 2019 - Finally, a little success!

After some growing pains with my astronomy club's new Celestron CGX-L, I finally saw a glimmer of hope!  I am successfully acquiring images.  Short images, but images nonetheless!

I arrived out at the observatory about 20 minutes after sunset and immediately started setting up a timelapse.  It's fun to watch the dome move as the sky darkens and the stars slide across the sky.  Next, I got the memorial dome opened up, my cameras attached, computer hooked up, and covers off.  I turned on the mount, and the hand controller gave me the same error as last time after I input the time and date -- it said no stars were available above the filter (I checked, it's set for 20-90 degrees in altitude).  So I did an audacious thing to do with a Celestron telescope -- I unplugged the hand controller!  Tonight was going to be a computer-controlled night only.

Goodbye hand controller!

Hello USB!

I got the new Celestron PWI app booted up (it only works for their two USB-enabled mounts, the CGX and CGX-L, at the moment) and connected directly to the mount via the built-in USB-B port (woo hoo Celestron is now in the 20th century!  No more telephone serial ports!)

Then closed out of the alignment routine and opened the Slew dialog so I could rotate the mount 90 degrees for accomplishing polar alignment with SharpCap.  Polar alignment was a little over one arcminute off from last time, which isn't terrible, but isn't perfect either, so I adjusted it a bit. 



Once that was done, I flipped back over to the Celestron app and had it split-screen with SharpCap for alignment.  While slewing around, the hilariously short power cable that came with my ZWO ASI1600MM Pro almost broke off of my camera, and it prevented the mount from slewing twice as I furiously tried to get it unhooked from the mount.  There is no good place on the mount to place the power converter box where it can actually reach at all angles!  I'm going to buy an extension cable. It uses the standard 2.1mm barrel connector, so it shouldn't be too hard to find.  To be safe, I re-homed the mount, powered off and on, and re-started alignment.

The camera is a loooong way from the mount.

Once I had about five stars added, I hit the "view alignment" button, but it froze the app!  I waited for several minutes, but it was still frozen.  So I begrudgingly force-quit the app, restarted it, and then had to perform the whole alignment again because I didn't save the first one before trying to click that button.  Lesson learned!  I saved it as soon as it was complete the second time.  That is one nice thing about using the app instead of the hand controller -- as long as no one else touches the polar alignment, I can plug in any one of my computers and re-load the last alignment model.  This will be really helpful for when other people use the telescope and don't hibernate it when they're done!  Should save me some time.

With alignment complete, I had a choice to make.  I wanted to image with my new hydrogen alpha filter, and I really wanted to image the Horsehead Nebula.  It's getting pretty far in the west now, however, and I would only be able to get two hours on it, at best. Another option was the Rosette Nebula, which is a good bit higher, but it's too large for the 0.6x0.9 degree field of view of my ZWO camera on the Meade 127mm ED apo f/9 that's in the memorial dome.  It has a focal length of 1143mm (which, as a refractor, as part of the reason my camera is so far from the mount -- and the fact that it has so much backfocus, the focuser is nearly all the way extended!).  To the east, it's Galaxy Season, mostly the itty bitty ones.  Some of those would love a hydrogen alpha channel, but I don't want something like that for my first Ha target.  So I decided to image it anyway and get what I could, and then maybe find another target at 11 PM.

I slewed over to the Horsehead, but I don't see a Precise Goto option in the Celestron app, so I opened up Sequence Generator Pro to give it a try.  I couldn't figure out how to make that plate solve, though, so I will need to do some further reading.  I also had AstroTortilla handy, however, so I swapped over to that.  As it turned out, it was quite close - only off by about 2 minutes of declination, and some fraction of a second in RA.

I turned on guiding, then took a 3-minute image.  And there it was!

Next, I took a 5-minute image.  It looked great!  Until I zoomed in on the stars...

I checked guiding, and it wasn't absolutely awful, but it wasn't great either, especially with that long focal length.

I took a second 5-minute frame just to check, and it was equally bad.  So I set the exposure time back to 3 minutes, which hurt to do with a hydrogen alpha filter, but hopefully I'll still get some good signal-to-noise ratio once I stack.

I went and checked on it after about a half hour, and the frames still looked good.  I rotated the dome and went back inside -- my thermometer read 35F!  But no breeze, so that was good.  I took a moment to admire the sky.  Earlier in the day, I kept an eye on the distant buildings on the horizon, which I use as a gauge of atmospheric condition for imaging.  It was unusually clear today, which was very promising.  The sky was a rich, clear blue all day, and the Clear Sky forecast predicted 3/4 seeing and 4/5 transparency, and zero clouds, at least until about 1 or 2 AM.  This all meant that the light pollution haze in the west wasn't as bad as usual, and there were quite a few stars and star clusters visible.

While I was warming up in the warm room, I scrolled through available targets in SkySafari.  I came up with two options: M82 (Cigar Galaxy), or the Cone Nebula.  I have been dying to image the Cone Nebula, but didn't get out much this winter to do it.  I did try earlier this winter, but had some issues getting on target.  It is getting lower in the sky was well, but it's higher than than Orion's Belt, where the Horsehead Nebula is.  On the other hand, M82 would just be crossing the meridian, and it has two massive jets that glow brightly in hydrogen alpha light that I have been unable to capture on my DSLR or even my ZWO camera.  I do have a pretty robust dataset on the ZWO camera of LRGB data that I could add the Ha to...but, it's on the Vixen telescope that used to be there, which had a shorter focal length (800mm) and a larger field of view, so I would have to like crop the image right around M82 or something and process with that...more complication than I have time for.  Cone Nebula it is!

The hard part is slewing to it.  It's actually a dark nebula structure right next door to NGC 2264, the Christmas Tree Cluster, and the whole Cone Nebula area is known as NGC 2264.  It's much larger than the FOV of my current setup, so slewing to that would not have the actual cone part of the Cone Nebula within my FOV.  I couldn't get SkySafari to select one of the stars near it either to get coordinates to enter into the Celestron app to slew to.  Then I remembered that I had just installed Cartes du Ciel over the weekend, an observing planning application that can also control your telescope.  So I searched for NGC 2264, zoomed in on that area, downloaded the DSS (Digitized Sky Survey) image for that area, and saw where the Cone itself was.  I right-clicked, told it to center that object on the screen, connected the telescope to the app (really the Celestron PWI app, which is also an ASCOM driver for the mount -- very handy!), and then told it to slew to that spot.  And off it went!  Right to that spot!  I took a test image, and there it was!

Pretty dim, but hopefully it will come out in stacking.  Unfortunately, for some reason, when I had Cartes du Ciel open, it turned off my camera's cooler, and once I closed the app, the cooler started again.  I didn't think CdC talked to the camera, and SGP was still able to trigger it and download images, so I'm not sure what's up there.  As soon as I closed CdC, the cooler kicked back on (I could see the temperature dropping in SGP and hear the fans).  Weird.

I wrapped up at midnight since I needed to be at work the next morning!  It was too bad, since the sky was gorgeous, and the moon wouldn't cross the horizon until after 1 AM.  Unfortunately the weekend is looking rainy, but there may be a night or two next week that clears.

[March 28, 2019]


Horsehead Nebula

I did a quick-process on the Horsehead Nebula data last night since it was getting late and I needed sleep, but boy did it come out awesome!  

Date: 26 March 2019
Object: Horsehead Nebula
Attempt: 2
Camera: ZWO ASI1600MM Pro
Telescope: Meade 127mm ED APO f/9 (club's)
Accessories: Astronomik Hydrogen Alpha CCD T2 12nm filter
Mount: Celestron CGX-L (club's)
Guide scope: Celestron 102mm
Guide camera: QHY5
Subframes: 17x180s (51m)
Gain/ISO: 139
Stacking program: PixInsight 1.8.6
Stacking method (lights): 
Post-Processing program: PixInsight 1.8.6
Darks: 20
Biases: 0
Flats: 0
Temperature: -30C (chip), 27-35F (ambient)

When this came out of stacking, my jaw hit the floor!  It was so exciting to see a group of dim, noisy images become a thing of striking beauty. I got such better signal on the glowing backdrop of the Horsehead than I have before!  Here are a few previous attempts, in wideband:

Date: 4 November 2016
Object: Horsehead Nebula
Camera: Nikon D5300
Telescope: Celestron C11
Accessories: Orion SkyGlow filter, f/6.3 focal reducer
Mount: Celestron CGE
Guide scope: Orion ST-80
Guide camera: QHY5
Subframes: 17x300s (1h25m)
ISO/Gain: ISO-3200
Stacking program: DeepSkyStacker
Stacking method (lights): 
Darks: 8
Biases: 20
Flats: 20
Temperature: 37F

Date: 17 February 2017
Object: Flame & Horsehead Nebulae
Camera: Nikon D5300
Telescope: Vixen na140ssf
Accessories: Astronomik CLS filter
Mount: Losmandy Gemini II
Guide scope: Celestron 102mm
Guide camera: QHY5
Subframes: 25x180s (1h15m)
ISO/Gain: ISO-1600
Stacking program: DeepSkyStacker
Stacking method (lights): 
Darks: 30
Biases: 20
Flats: 20

I also got much sharper detail this time.  This is all despite the fact that it was well inside the light pollution area of the sky in the west that I don't usually image in, and it was getting low on the horizon!  

The Horsehead Nebula is part of the much larger Orion Molecular Cloud Complex.  The head-shaped structure itself is a dark nebula -- a cloud of molecular gas that absorbs light.  Molecular clouds include both organic and inorganic molecules, and lots of interesting low-pressure chemistry happens there that can't happen on Earth.  It lies about 1,500 lightyears away.  Behind the Horsehead is a cloud of hydrogen gas that emits on the hydrogen alpha wavelength my filter was built for.  The shape of that glowing nebula (also known as IC 434) is due to the stellar winds of stars in that vicinity that sculpt it.

Here are the steps I did in PixInsight:
- SubframeSelector to cut less-than-ideal frames
- BatchPreprocessor
- Bias: Average, linear fit clipping
- Darks: Average, linear fit clipping
- Reference frame: frame5
- Calibrated, registered
- ImageIntegration
- Combination: average
- Normalization: additive
- Weights: SSWEIGHT keyword
- Rejection: Winsorized Sigma Clipping
- Discovered image files out of BatchPreprocessor had lost all data but stars...master dark and bias look fine. Registered and calibrated images look weird
- ImageCalibration for calibration, with master dark & bias from BatchPreprocess
- Frames came out dark again.  Okay, hand-making master dark and master bias
- ImageIntegration for biases
- Average combination
- No Normalization
- Don't care for weights
- Linear fit rejection algorithm
- Saved bias and created superbias
- Calibrated darks with master superbias
- Integrated darks into master dark with ImageIntegration
- Calibrated lights with master dark & superbias with ImageCalibration
- Still weirdly dark!!
- Calibrated with just bias - still dark
- Calibrated with just dark - looks fine.  Something's wrong with the bias
- Pressing on
- Registered with StarAlignment
- ImageIntegration for registered, calibrated lights
- Same settings as above
- Cropped with DynamicCrop
- DynamicBackgroundExtraction
- Denoising with MultiscaleLinearTransform, with stretched lum mask
- Stretched with HistogramTransformation
- Cropped again (vignetting)
- Denoised with ACDNR
- CloneStamp for dust spot
- Done...for now

Cone Nebula

The raw frames for this one looked even dimmer -- I had to crank up the auto-stretch in order to even see it!  But I believe in the magic of stacking...let's see what it can deliver!

All right, so here's a single, raw, screen-stretched frame.  (Screen stretch means there's an estimated stretch that is applied to the image, but it's not actually stretched - the view of the image is stretched so I can see what I'm doing).

Single raw 3-minute subframe of the Cone Nebula

I used just the master dark for calibration again because there is something up with my bias frames.  I'll have to re-take them next time I'm out (even though they look fine).
Calibrated and registered single frame

Next came stacking -- and the air went out of my lungs!
Integrated image (15 frames)

Wow!  It just came right out!  So exciting!!

Then I did the rest of my processing:
- SubframeSelector: didn't eliminate any, but calculated weights
- frame3 has highest weight
- BatchPreprocessor for calibration and registration
- frame3 for registration reference
        - Only used master dark, since something wrong with bias
- ImageIntegration for stacking
- Combination: average
- Normalization: additive
- Weights: SSWEIGHT keyword
- Rejection: Winsorized Sigma Clipping
- Cropped with DynamicCrop
- Denoising with MultiscaleLinearTransform, with stretched mask
- DynamicBackgroundExtraction
- DynamicPSF generation for Deconvolution
- Deconvolution
- Made range mask on stretched copy
- Made star mask on linear image
- PixelMath for range_mask-star_mask to target bright areas of the image
- Used PSF and deringing
- Stretched with HistogramTransformation
- Denoised with ACDNR
- CloneStamp to remove dust spot
- Another round of denoising with MultiscaleLinearTransform
- CurvesTransformation touch-up
- One more round of MultiscaleLinearTransform denoising...with a mask with clipped shadows

Date: 26 March 2019
Object: Cone Nebula
Attempt: 3
Camera: ZWO ASI1600MM Pro
Telescope: Meade 127mm ED APO f/9 (club's)
Accessories: Astronomik Hydrogen Alpha CCD T2 12nm filter
Mount: Celestron CGX-L (club's)
Guide scope: Celestron 102mm
Guide camera: QHY5
Subframes: 15x180s (45m)
Gain/ISO: 139
Stacking program: PixInsight 1.8.6
Stacking method (lights): Average, winsorized sigma clipping
Post-Processing program: PixInsight 1.8.6
Darks: 20
Biases: 0
Flats: 0
Temperature: -30C (chip), 27-30F (ambient)

So awesome!  The noise is a bit high in this image, but only three minutes with a narrowband filter is less than ideal.  I will need to figure out how to improve the guiding on that mount!

More to come!

Sunday, March 24, 2019

#178 - Saturday, March 23, 2019 - If it's not one thing, it's another

Since I haven't gotten out much in the last couple months due to being away from home, I'm itching for some starlight!  The forecast was mixed across all my weather apps, with some showing clouds rolling in around 9, while others held off till midnight.  I figured it would probably be a bunch of that thin high hazy stuff, and besides, the moon was just a few days past full.  So I decided that it would be a good night for experimentation, since if things didn't go well, at least I hadn't wasted a good night.  I invited fellow astronomy club member Kevin out again, who is interested in learning astrophotography, and brought my Nikon D5300 and Vixen Polarie for him to play with while I worked on some stuff with the club's memorial telescope.  Fellow club member Rich was also out there, who was planning on doing some binocular observing.

I had three personal goals for the evening:
- Check to see if the polar alignment on the memorial scope held after I tightened all the bolts last time
- Measure how long it will guide for
- Acquire some images with my new Astronomik 12nm Hydrogen Alpha filter my uncle gave me :D:D

I opened up and plugged in the memorial dome, and booted up the mount, which unfortunately did not offer to un-hibernate itself -- it would appear that someone used it and didn't fill in the logbook (probably someone came out to qualify on it after last weekend's public stargaze), and didn't hibernate it.  So I would have to re-align, darn!  But first, I needed to check the polar alignment. Last time I was out, I polar aligned the memorial scope's Celestron CGX-L mount and tightened down all the bolts.  It appears to have helped -- I only had about an arcminute of error this time instead of over a degree, which isn't great, but was better.  I used the pro version of SharpCap to do the polar alignment, which is super handy and easy and just requires that you have a camera plugged into the scope, which of course I already have.  Luckily, whoever used it last weekend didn't adjust the focuser, so my camera as already in focus.  I tuned the polar alignment, and then set about doing the alignment.  However, after entering the time and date, the hand controller told me that there were no stars above the filter limits!  So I double-checked the time, date, time zone, and GPS coordinates, and all were accurate.  I re-booted the scope, but this was tricky because the hand controller has a backup battery so that you don't lose alignment during a brief power outage -- a handy feature at star parties, but at the moment, the bane of my existence in trying to do a hard reboot.  Unplugging the hand controller from the mount didn't help.  I finally got it to reboot, but still got the same warning.  Finally after a couple of tries, I got it to show me some stars, although it only showed like five.  One of them was Caph, which was indeed up, but very low in the north.  I also tried Castor, but it pointed the scope somewhere east that was definitely not anywhere near Gemini.

I went inside to flip through the manual on my cell phone and think about what to do, and the idea occurred to me to try running it through my computer, like what I used to have to do on the Losmandy Gemini mount we had in that dome previously because the hand controller's buttons stopped working.  So I went to Celestron's website and downloaded the PWI application to my phone, and then Bluetoothed it to my tablet (I couldn't get good enough cell phone reception in the area of the memorial dome to be close enough to tether my tablet to my phone, and the observatory's wifi was down).  Finally, I installed the program, plugged the mount directly into my computer via USB (the CGX-L has a dedicated USB port, meaning you can skip the hand controller entirely).  At last, a stroke of luck -- it connected immediately!  I went through the alignment procedure in the app, which unfortunately had far fewer stars to choose from than the hand controller.  It got a bit tricky though because I had to have the slew buttons window active in order to press the keyboard arrow keys to move the mount, but you couldn't minimize the main application and just have the slew buttons up, and I needed to also be able to see the camera image.  My tablet has a high-resolution screen, but it's still only 10 inches diagonally, and the Celestron app wouldn't properly half-screen; it still took up like two-thirds of the screen.  But the SharpCap window went half-screen well, so I was able to have both windows open at once and get the star in the crosshairs.  I added two western stars and one eastern, and called it good.  (Sorry I forgot to take screenshots!)

Okay, finally aligned.  Leaving my filter wheel attached because without it I can't get far enough away from the scope to focus (it has a looooong backfocus, which is very handy for astrophotography), I screwed on my new hydrogen alpha (Ha) filter to the end of the barrel, and checked that the filter wheel was on Luminance.  (In hindsight, I forgot that I had an empty slot that I could have used instead).  I slewed over to Betelgeuse to focus both my imaging and guide cameras.  My imaging camera on the main scope was not only in focus, but perfect focus already with the Bahtinov mask!  Even with the added filter (which didn't add any length since it went inside the tube, but a filter's index of refraction can sometimes change the focal point ever so slightly).  You know, I always say I want more people to use the memorial scope, but secretly I don't because I like not having to re-focus and re-align every time I go out there ;)  I checked the guide camera focus, and it was good enough.  Then in the Celestron app, I wanted to slew to the Horsehead, but it's not in the Celestron catalog, nor are any Barnard catalog numbers, so I just went to the Flame instead to test (which it doesn't know by name, but the Flame Nebula does have an NGC number, NGC 2024).  I saw that Alnitak, the leftmost Orion's Belt star, which is right next to the Flame, was a bit up and to the right, so I slewed the scope using my keyboard again down a bit to get it where I wanted based on looking at the orientation in SkySafari.  After calibrating the autoguiding app PHD (which also went smoothly, thankfully -- the Celestron PWI app showed up as a driver!), I acquired a 3-minute test image.  And there it was!  Unfortunately, since I was in SharpCap, it didn't save :( But it looked quite nice.

I wanted to image the Horsehead Nebula though, so I pulled up the celestial coordinates in SkySafari, slewed there, and then flipped over to Sequence Generator Lite to start imaging.  (I like the way it names files, the stuff it puts in the FITS header, and other features that are easier to access than in SharpCap.)  PHD's guide graph was not looking good (again, forgot a screenshot, but my total RMS was like 2 arcseconds).  Then, Sequence Generator kept crashing when it tried to connect to the camera.  So I went back to SharpCap, and it wouldn't connect either!  I unplugged and replugged the USB cable for the camera, but no dice.  So I quit PHD and the Celestron app and unplugged the USB hub, then plugged back in.  Camera was back, woot!  I opened it in Sequence Generator, set the settings, re-started PHD (it saves the last calibration by default now, which is super handy), and also restarted the Celestron app (it needs to be running for PHD to talk to it).  But when I went back over to the Celestron app, it did not save the alignment!  And I couldn't even find any buttons that would have let me.  I decided to experiment with going through the hand controller USB instead of directly to the mount so I could test whether it would save alignment if I went that way, and I was able to connect.  By the time I added a couple of alignment stars and got back on the Horsehead Nebula, it was dropping down below the main observatory building, and there was a bunch of cloud cover.  So much for that.

But I was back up and running, and wanted to image something.  I flipped through the SkySafari "tonight's best" list to see what glowed in hydrogen alpha that was up, which in the springtime isn't much because it's galaxy season.  (I am really excited to use my Ha filter to get the gorgeous red star forming regions in other galaxies, but since this was a test night, I wanted a big easy target like a nebula).  M82, the Cigar Galaxy, was on the list, and it has giant hydrogen jets coming out of it that I have been dying to capture.  So I slewed over to there, started acquiring, aaaand I swear I heard the scope slew or something, and then guiding was just totally borked, even after I acquired a new guide star.  Finally I threw in the towel -- it was almost midnight, the clouds were getting thicker, and the moon was rising, so I a) wouldn't be able to do a proper guiding test because the bad atmosphere would mess with the results, and b) I wouldn't be able to get any good hydrogen alpha images.

One thing I did achieve for the evening was setting up a timelapse on the memorial dome.  I only got about 26 seconds of video out of it, and it's not terribly exciting, so I'll hold onto the clip for an observatory compilation video I'm planning on making this summer.  But timelapse video can be dual-purposed as a star trail image too, so here's that!

In addition, Kevin got some practice focusing the 55-200mm lens on my Nikon D5300, although he ended up not imaging because he was watching the live entertainment show of me struggle-bussing with the Celestron CGX-L instead.  😂 Rich also joined the show and didn't even pull out binoculars!  It was indeed an instructive evening.  I got to try out the new Celestron mount control software and see all the features it lacked that I needed (where's Precise Goto?  Goto home position?  Save alignment?  Load last alignment?  There was a "configuration" button that had some stuff in it, but not even half of what you can access from the hand controller!), and I got to try out my hydrogen alpha filter.  Hopefully next time I can get some good results!  And I'll come prepared with either having this software figured out, or having some other piece of software to control it.

Friday, March 22, 2019

#177 - Monday, March 11, 2019 - Sharing the Love

I know it's been a minute since I last posted!  I was doing a thing for work for six weeks out of town, and obviously I didn't want the whole internet to know that my apartment was empty.  I took the lunar eclipse images there, having brought my camera gear for that exact purpose.  Then I was out for a week touring the graduate schools I got into before I had a chance to write a log entry for this night or work on processing the data.

It was exciting to be back out at the observatory!  It was a chilly night, below freezing, but it was clear and the moon was only a crescent, so it was worth it.  The ground was very squishy after all the rain we had gotten earlier in the week.  I brought out my ZWO ASI1600MM Pro and QHY5 guide camera to use my astronomy club's memorial dome setup (Celestron CGX-L with a Meade 127mm ED apo refractor, f/9), both of my DSLRs (Nikon D5300 and D3100), and my new Sky-Watcher Star Adventurer.

The forecast was pretty promising, and the moon was a small crescent, so imaging wouldn't be too hindered by it.  One of my fellow astronomy club members, Kevin, asked me to show him the ropes on astrophotography, so I invited him out as well.

I got out there a little after sunset, and upon signing into the log, noticed that no one had been out to the observatory in nearly a month!  There had been quite a bit of weather in the prior month, so a few things weren't working; I had to hit the reset button on the GFI outlet that the memorial dome plugs into, and the central building heater didn't kick on, so I used the two room heaters in the warm room instead, which got it up into the 60s in there at least.  The ground was very squishy from recent rain.

While I waited for Kevin to join me, I started polar aligning the Star Adventurer.  I had practiced in my hotel room on my work trip before the lunar eclipse, but hadn't actually had a chance to polar align it outside yet, so I referred back to the manual.  First, I needed to make sure it was calibrated, which is done by rotating the RA axis and seeing if the crosshairs in the polar scope moved against the background.  They did, which requires you to use a tiny hex wrench to adjust the position of the etched pattern plate inside the polar scope.  After some adjustment, however, it ended up coming loose, so I took it inside to get it back into position after unscrewing the eyepiece-thing.  While I was tightening the screws back up, I realized a screw was missing!  So I wouldn't be able to calibrate it.  I also couldn't get it positioned quite correctly with the eyepiece thing, so it's out of focus.  (At first, I had it in upside down!  But I fixed that, and it's still not quite at the focal point.)  So I abandoned trying to actually polar align it, and just did a rough alignment using a compass, the altitude indicator, and a polar alignment app on my phone showing where Polaris should be on a polar alignment circle for your location and time.  I hoped it would be close enough.

Kevin came, and I set up my Vixen Polarie for him to use while I played with the Star Adventurer, and I attached my Nikon D3100 to it with my 50-200mm lens at 95mm, f/5.  I got the Polarie connected to one of my external cell phone batteries for power, and showed him how I find the target and focus the lens.  I went for an easy one: the lower half of Orion, to include M42, the Flame Nebula, and the Horsehead Nebula.  I had a hard time finding focus though - the stars would pixelize in my 5s exposure, which usually means I'm in focus, but they looked a little fat still.  I always have a hard time finding infinity focus on that lens -- it's a really small spot!  I checked around that point, and couldn't get any closer, so I decided just to roll with it, mainly because it was cold.  I did a couple of test exposures to find how long I could expose for with my rough polar alignment, and I got up to 90s before it started to show star streaks, so I just rolled with that.  Orion was getting closer to the western part of the sky, where there's a fair bit of light pollution, so I hoped it wouldn't be too hard to process.

We went inside to warm up, and I kept fussing with the Star Adventurer, but couldn't get the pattern plate situated right still, so I gave up for the night.  After we were warm, I brought Kevin out to the memorial dome to show him how I polar align it with SharpCap.  I got to within a few arcseconds of perfect, and then I tightened down all of the bolts on it.  I've been having trouble with it "slipping;" every time I go out there, the polar alignment error is back up to like 40 arcminutes or more.  So we'll see if it holds this time.  I know it's not the pier because the Losmandy Gemini we had on there previously, while I never checked the polar alignment, was so spot-on and rock-solid that I could guide for at least 25 minutes (I checked one hazy summer night).  Once that was done, Kevin had to head out.  After he left, I re-aligned it, and by the last two calibration stars of the four I entered, it was hitting pretty close to perfect on the gotos.  After that, I decided to call it a night as well -- it was 11:30 PM, and I had to work the next day.

On my drive home, I saw something big and orange out of the corner of my eye -- it was the setting crescent moon, lying on its back!  It was enormous, and was just kissing the horizon.  Time for it to light up someone else's night.

Processed Image

I finally got to process the data on Orion on March 19th.  It turned out to be a difficult dataset for a couple reasons:
1) The stars were a little bit stretched from tracking
2) I couldn't quite achieve perfect focus
3) It was getting near the light pollution to the west
4) I only wound up with about 31 frames after ditching some to tracking error and cutting some during subframe selection

So I didn't spend a ton of time massaging it, but hey, it's still a decent picture of outer space!

Date: 11 March 2019
Object: Orion Widefield
Attempt: 4
Camera: Nikon D5300
Telescope: Nikon 50-200mm lens @ 95mm, f/5
Accessories: N/A
Mount: Vixen Polarie
Guide scope: N/A
Guide camera: N/A
Subframes: 31x90s
Gain/ISO: ISO-1600
Stacking program: PixInsight 1.8.6
Stacking method (lights): Average, linear fit rejection
Post-Processing program: PixInsight 1.8.6
Darks: 40
Biases: 30
Flats: 0
Temperature: 25F?

I processed it all in PixInsight, including calibration & stacking.  Here's the quick rundown of the steps I did:
- SubframeSelector; weights calculated, used for image integration
- Used BatchPrepcrocessor to create master dark, master bias, calibrate, debayer, and register the lights
- ImageIntegration with Additive in Normalization, Average in Combination, FITS keyword SSWEIGHT, and linear fit clipping for rejection
- Cropped with DynamicCrop
- DynamicBackgroundExtraction for background removal, initial color correction, gradient reduction
- PhotometricColorCalibration
- Denoising with MultiscaleLinearTransform (forgot luminance mask...)
- Dust spot removal with CloneStamp
- Deconvolution with DynamicPSF, 30 iterations, range_mask-star_mask protection, deringing
- Stretched with HistogramTransformation
- CurvesTransformation
- Tried HDRMultiscaleTransform, didn't like result
- Denoising with MultiscaleLinearTransform, with luminance mask

And now Kevin has a decent dataset to practice and learn how to process in something like DeepSkyStacker.  Best of luck!