Saturday, August 17, 2019

#201 - Saturday, August 3, 2019 - Final Members Night

With the movers coming on Monday to pack up my house for my move to California to start my PhD at UC Berkeley, I attended my last member's night with my astronomy club.  There was a pretty good turnout of about 20 people, along with a few who were camping on that nice weekend in trailers.  The forecast was iffy on the cloud situation, meaning that there would probably be some high-altitude scuzzy stuff.  Sounded like a perfect night to test out a new camera!


At least the clouds were pretty!

I didn't feel like bringing all of my gear, especially for an iffy forecast, so I planned on using one of the club's telescopes: an 8-inch Celestron Schmidt-Cassegrain on a Celestron CG-5 mount.  The new camera was one that my astro-friend John had very generously given to me recently: a ZWO ASI294MC Pro. It's the successor to my ASI1600MM Pro, but the color version. I had planned on buying the color version of my monochrome camera at some point for outreach events, transient phenomena (comets, Jupiter shadow transits, etc), and short nights, but now I have one much sooner! It would be a good night to test it anyway since I didn't have a way to mount my guidescope on the C8, so I'd just do short exposures until the cloud situation became unfavorable.


After some potluck dinner (theme: "Pies & Pints," for which I brought an apple pie), the thin crescent moon was setting in the west, and I grabbed some video on it before it dipped below the trees.  As I was prepping to move to Jupiter, someone spotted a weather balloon, and I just caught a glimpse of it in our 16-inch Dob!  But it had dropped its payload, separated, and deflated before I got my telescope over in its direction.  Darn, so close!  (And a perfect application for a one-shot color camera!)


I also enjoyed some yummy cake that some of my astro-friends got for me!


Having missed the weather balloon, but it not being quite dark yet, I imaged Jupiter and Saturn.  The atmosphere wasn't that great, however, so I'll have to see how those come out.

I didn't end up doing any deep sky imaging, but I did observe a dim M22 globular cluster, as well as M13, through the Dob.  I hung around until 11:15 PM, and then packed up and bid farewell to many of my astro-buddies.  It was a bittersweet goodbye, but we will be sure to stay in touch on social media.  I will miss them all dearly!

It has seriously been one heck of a ride so far.  After going it on my own for about 6 months after I got my first telescope in July 2015, a friend in the local astronomy club convinced me to check it out, so I went to a members night with him in February 2016, and joined the club shortly thereafter.  It was at that members night that my uncle messaged me asking if I would be interested in his Celestron computerized German equatorial mount and 11-inch Schmidt-Cassegrain, which really upped my game in astrophotography, especially once I figured out how to guide.  I also got to use a lot of astronomy club equipment, in addition to the awesome observatory facility we have (and really under-use!).  Many of my favorite images were taken on club equipment! Many club members gave me advice, tips, and even equipment, and even more gave me encouragement and friendship.  I cannot thank enough the many people in that club who have helped me along the way! 

Clear skies, and I hope to catch you at the next star party!  (And don't worry, I've already found the astronomy club of the East Bay area!)


Friday, August 16, 2019

#200 - Friday, August 2, 2019 - Outdoor Outreach

For the last three years, I have averaged 50 nights of outreach per year.  I almost made the mark again in my fourth year -- hit my 200th astronomy night just two weeks after my fourth anniversary of amateur astronomy!  Still going strong :D  Of course, many clear nights at the Texas Star Party and in Chile helped.  We had a lot of clouds this past year in my Midwestern home location.

For my 200th astronomy night, I did an outreach event at a county park about a half hour from my house, where I've done a few other outreach events and talks.  The movers were coming on Monday to pack up my stuff for my move to California (I'm starting my PhD at UC Berkeley!), and they offered to come Friday, but I said come Monday and Tuesday instead! This let me still have the mount on my outreach telescope, my Celestron NexStar 8SE.  (My plan was to take the telescopes with me in my car, and let the movers take all my mounts).

I was really glad I had my outreach scope because there were a ton of people there!  It was largely an event for kids, and there were about 30 people or so there total.  We had two other astronomy club members present with telescopes as well, but we each still had lines to look through them.  Several other club members came out without telescopes to support.

First, I pointed my scope to the thin crescent moon that was sinking into the west, which was quite beautiful both with and without the telescope.  We got a little bit of earthshine on the darkened portion before it set.  I didn't have my DSLR, or else I would have grabbed some shots!  Next, I pointed it to Jupiter, which had the Great Red Spot for about twenty minutes before it slid around the  back of the planet, and then I moved over to the crowd-pleaser and personal favorite: Saturn.  It's always an absolute delight in my 8-inch, and despite some waviness from the primary mirror still cooling off, it did not disappoint!

At one point, a young girl (maybe about 9 or 10?) was over at my compatriot Phil's scope, and he was telling her about how the computer-driven mount worked.  She said she wanted to be an astronomer, which of course was very exciting.  When Phil gave a command for the scope to slew somewhere, her jaw positively dropped!  It was a lot of fun.  I let her control my scope later, and answered some questions about black holes and other space things.  I told her about the Event Horizon Telescope after I showed her the recent radio-wavelength image of the black hole at the center of galaxy M87, and about the incredible resolution of the effectively-Earth-sized telescope (achieved through advanced interferometric processing algorithms).  The resolution of this telescope collaboration would be equivalent to imaging an apple on the Moon, or reading a paper in New York from a cafe in Paris!


I missed the moment of maximum jaw droppage, but she was very impressed!

After the last few people left around 10:30 PM, I set up my ZWO ASI1600MM Pro with my electronic filter wheel onto my 8-inch, including the IR photometric filter I had recently added to the previously empty slot.  The seeing turned out better that night than expected, and I got some very nice results of Jupiter and Saturn!  I've only processed Saturn so far,  but I'll put up Jupiter when I get to it.

UTC: 3 August 2019, 03:51:09
Object: Saturn
Attempt: 20
Camera: ZWO ASI1600MM Pro
Telescope: Celestron C8
Accessories: Astronomik RGB Type 2c 2-inch filters, Schuler IR Johnson-Cousins photometric filter, 
Starlight Xpress filter wheel
Mount: Celestron NexStar SE
Frames: IR: 345/1000
R: 713/1001
G: 537/1000
B: 413/1000
Exposure: IR: 250 ms
R: 120 ms
G: 120 ms
B: 200 ms
ISO/Gain: 300
Stacking program: RegiStax 6
Processing program: PixInsight 1.8.6

It's quite small in the field-of-view of my camera, so this is cropped quite heavily, so I don't have great resolution (pixels) on it.  But when I eventually live somewhere where the seeing conditions are good enough to support using a Barlow or eyepiece projection, I definitely will do that!

I love outreach events!  They give me so much energy and joy :D






Thursday, August 15, 2019

#199 - Tuesday, July 23, 2019 - New Scope!

I checked the evening forecast when it was clear earlier in the day, and it looked promising, so I used some award days off I'd earned to go do some astronomy and process some Chile photos.  One of my friends from the astronomy club, Rikk, gave me a Vixen 8-inch f/4 Newtonian in June, which I was very excited to try out!  It was a little heavier than my 8-inch SCT or my Takahashi, so it would also be an experiment for how well my Celestron AVX could handle it.

I loaded up the car with the scope, mount, ZWO ASI1600MM Pro camera, my tackle box of astro accessories, table, chair, tablet computer, and eyepiece case, and got out to the observatory around 8:15 PM.  I got everything assembled and balanced in not too much time.  I left the scope rotated up with the camera on top because I hadn't installed a finerscope/guidescope dovetail on the other side yet.


It may look front-heavy with the camera, but the primary mirror is where all the weight is in this telescope, so it balances out pretty closely.  

I realized on the drive over that I had forgotten to grab a guidescope, so this would also be an experiment to see how long the mount could track for without guiding.  The focal length on this scope is 800mm, so not too long to catch every error, but not so short as to hide all of the error either.  

Rikk said it probably needed some collimation, so I pulled out my laser collimator and hit up the internet to see what I needed to look for.  I looked down the tube, and the secondary seemed pretty close to the center of the primary, but the primary didn't have a center dot, so I couldn't tell for sure.  Shining the laser light down the tube through the eyepiece, I couldn't see the return dot on the collimator, but it might have already been in the very center.  I decided not to mess with it and I'd wiggle things around in daylight to see exactly where that spot was at.  But it seemed close enough, unless the dot was all the way off of the collimator or something.  But I could see my eyeball in the secondary when I looked through the empty eyepiece tube, so I took that as a good sign.  

Another thing I realized I forgot was the power cable to my mount...things are still mixed up after the Texas Star Party.  Luckily, the club owns a couple of Celestron mounts, so I borrowed one of the power cables from those.  It was still pretty bright out by the time I finished putting everything together, but Jupiter was readily visible in the twilight, so I slewed over there to check whether I could achieve focus.  First, however, I needed to align the finderscope, so I pointed it at a distinctive treetop, got the image centered in the camera's view on my computer, and adjusted the finderscope to match.  Then I could find Jupiter.  Once there, I was able to achieve focus!  Better yet, the focuser was racked pretty far out, which meant that I had a good amount of backfocus to play with as far as adding additional accessories in the future, like an off-axis guider, better focuser, or rotator.  

I slewed back to the home position and started polar alignment using SharpCap, which went smoothly.  Alignment went pretty well as well, with each star plopping into the field-of-view on the first guess.  Always a great start to an evening!


It was still pretty light outside when I was done setting up, but Jupiter was shining bright in the twilight, so I slewed over there to get focused.  I realized that the finderscope wasn't even close to aligned, so I slewed over to a distinctive tree and looked at the camera image on my tablet to get the finderscope aligned.  Once that was done, it was easy to find Jupiter, and I was able to achieve focus!  Better yet, I had to rack the focuser pretty far out, which meant that I had a good amount of distance to be able to add other things in the future, like a better focuser (or an electronic one), an off-axis guider, or a rotator.

I slewed back to the home position to do the polar alignment, which went smoothly.  Then I went through the alignment routine, which placed all of the stars in the field-of-view of the camera, woot!  Makes my life easier, and it's a good sign that the mount is going to cooperate that night.

With alignment complete, it was time to choose a target.  I had a number of criteria to consider: it couldn't be too small, but I also didn't want one that would fill up a large amount of the FOV, since I saw that there was some vignetting, and I wasn't sure about the collimation.  (I did have a coma corrector on too, by the way).  I wanted something bright that I could expose for 30s or less, since I didn't have a guidescope, but I also didn't want something I already had a good image of already -- with a clear night, I wanted some new images!  There were a few galaxies westward that would make good targets, but that's right in the thick of the light pollution from the nearby city.  I thought about doing the Cocoon Nebula, since I haven't imaged it with my monochrome astro camera yet, but I knew I wouldn't get a whole lot of signal in the blue and green, and wanted to do longer exposure times for that one, especially to get a good view of the dark nebula.  I finally settled on the Iris Nebula, which was well-positioned, bright, and I didn't have a good image of it yet.  Bonus, the bright star in the middle would be really pretty with diffraction spikes :D  One of the things I'm really looking forward to with a Newtonian.

I took some test shots, and at 60s, the stars were nice and round!  My little AVX was still performing great.  This was really exciting.  On the left part of the image, the stars had a bit more of a donut-shape to them, so I figured this must be an effect of non-perfect collimation.  I tried for 120s, but the stars showed some stretching, so I dropped to 90s.  Some frames showed periodic error, but several were good, so I went ahead and pressed with that.

Single 90s luminance frame on the Iris Nebula

I set up my SequenceGenerator Pro sequence for 2.5 hours of LRGB imaging, and it was 10:30 PM by the time I started the script.  The sky was clear and had good transparency -- I could see quite a few stars.  There was so much light pollution though compared to Chile!  I missed it already!  The temperature was very nice, only requiring a light jacket, and there was no wind at all.  However, the humidity was really high!  Luckily, it takes quite a lot to dew up a Newtonian, and I didn't get any dew that night.

I hung out inside on my laptop, and then went back out at 1:15 to go pack up.  The moon was just rising in the east, still behind the trees.  Some clouds had rolled in though, including over my target!  So I'd have to see how many frames I'd get from the green and blue channels, which ran last.  I left the observatory around 1:45 AM, and enjoyed a gorgeous yellow-brown half-moon on the drive home.  A successful night!

[ Update August 15, 2019 ]

I actually got this image processed on July 25th, but I was still getting caught up on blog posts from Chile, and I haven't had time to finish this one during my move to California.  It came out fairly noisy due to low numbers of subframes, but otherwise surprisingly decent!

Date: 23 July 2019
Object: NGC 7023 Iris Nebula
Attempt: 4
Camera: ZWO ASI1600MM Pro
Telescope: Vixen MyStar G-R 200S f/4
Accessories: High Point Scientific coma corrector
Mount: Celestron AVX
Guide scope: N/A
Guide camera: N/A
Subframes: L: 29x90s
   R: 9x90s
   G: 10x90s
   B: 5x90s
   Total: 1h19m30s
Gain/ISO: 139
Acquisition method: SequenceGenerator Pro
Stacking program: PixInsight 1.8.6
Post-Processing program: PixInsight 1.8.6
Darks: 20
Biases: 0
Flats: 0
Temperature: -25C (chip)

The Iris Nebula, or NGC 7023, is a bright reflection nebula, where a star is surrounded by gas and dust, some of which reflects the light of the star.  The star in question is magnitude +7 star SAO 19158, which is actually a double star, whose companion is +13.4 magnitude and lies 2.3 arcseconds away, or 1,220 astronomical units (Earth-Sun distance), from the brighter star.  The nebula lies 1,300 lightyears from us in the constellation Cepheus, and spans 6 lightyears.

My PixInsight process:
- Created master bias and superbias with ImageIntegration and Superbias
- Calibrated darks with superbias with  ImageCalibration
- Created master dark with ImageIntegration
- Calibrated lights with master dark and superbias with ImageCalibration
- Still issue with bias frame (I think it's all the -25C biases), so calibrated light with just bias-cal'd dark frame, which looked fine
- SubframeSelector
- Scale: 0.98 arcsec/px
- Gain: 0.59 e/ADU
- Registered with StarAlignment, with highest-scoring L frame as referece
- Stacked with ImageIntegration
- L: Linear Fit clipping
- R,G,B: Winsorized Sigma clipping
- Cropped with DynamicCrop
- Applied DynamicBackgroundExtration to each channel
- Applied LinearFit to the RGB channels, with L as reference
- Combined RGB channels
- Denoised L & RGB with MutliscaleLinearTransform, with luminance mask
- Color corrected with PhotometricColorCalibration
- Stretched L and RGB with HistogramTransformation
- Had to adjust each color channel individually, since blue peak much wider than red and green
- Adjusted colors with CurvesTransformation
- Denoised with MultiscaleLinearTransform, with lum mask
- HDRMultiscaleTransform, 7 iterations
- More curves
- Denoise with ACDNR

Looking forward to more from this scope!



Thursday, August 8, 2019

#198 - Wednesday, July 10, 2019 - Last Dark Night of the Atacama

This morning, I was only able to sleep in until 10:30 -- it was too warm inside, and I became worried about whether the cameras I had left running on my Sky-Watcher Star Adventurer would have moved far enough to hit the mount or something.  So I got up and went to check -- all was well.  I shut off the power, put the batteries on their chargers, and grabbed my Nikon D5300 off of the mount for use later in the day on our adventures.

We tried again to visit the Valle de la Luna, this time arriving before 1 PM.  It was a beautiful park for not having a single living plant!



The moon over the Valley of the Moon!

One of the stops along the way was to a hiking trail that went up to the top of some part-sand dune, part-rock hilltops, as high as 8400 feet above sea level!  By the time we got to the top (after several stops to rest), it felt like I had just run a 5k!  But the view was incredible, and standing on a particularly tall rock made me feel like I was standing on top of the world.


We hit a few more stops along the way, including some old salt mines.


All of the white stuff in the rocks is salt.

At the end of the road was the Tres Marias rock monument, which was really cool looking.  I had to wonder how it was formed!


The miners would pray here for safety.

On the way back to the Atacama Lodge, we stopped for gas in San Pedro de Atacama, at their one Copec gas station that was in a really weird and rather hard-to-find spot.  It also had a long line.  We decided to wander around town for a bit and hit up some ice cream and pick up some gifts.  We also walked through a really old church that was built sometime before 1557!  The ceiling was made of dried cactus, which was really cool.


We drove back to the Atacama Lodge and watched the sun set. I set up my Nikon D3100 to do a day-to-night timelapse, and I got the cameras booted up on my Sky-Watcher Star Adventurer.  I pointed the Sony a7s with the Rokinon 135mm f/2 lens I was borrowing from the owner of the Atacama Lodge, Alain, over to the Rho Ophiuchi complex, which I've tried to image several times from various locations with varying levels of success.  I had to position the camera carefully so that I wouldn't pick up Jupiter's camera-saturating glow.  

Also attached to the Star Adveturer was my Nikon D5300 with my 70-300mm lens, and I was going to do M16 & M17 up in Sagittarius.  However, it was too close to where the Sony was pointed, and the cameras were hitting each other.  So I just picked a spot further south in the Milky Way and figured I'd see at least something interesting there.  

Once that was all set up, I went back to the cabin to have some dinner (leftovers we were trying to finish off), and I got my stuff most of the way packed up for departing Chile the next day.  :(  I went to bed at 9:45, and the plan was to sleep till 2, get up and do some observing, and hit the road by about 4:45 to drive to Calama to catch our flight out.

At 2 AM, I dragged myself out of bed, got dressed, and finished packing.  I went up to the rolloff shed and packed up my cameras and Star Adventurer as well, and then went and joined my travel companions John and Beth at the telescopes.  Alain was just putting the finishing touches on a behemoth 45-inch Dobsonian he'd spent the last few years building, and we were hoping to get first light through it!  We helped him collimate it, although we couldn't quite reach collimation -- he would need to move the focuser hole inward a bit toward the primary (a task he'd set about doing soon).  But it was close enough for first light.  We brought the tall ladder over, and with each of us taking turns holding up the scope since the counterweights weren't quite right yet, we turned it to the obvious choice of first-light targets: the incredible Tarantula Nebula, in the Large Magellanic Cloud.  The stars weren't quite pinpoint because of being not quite in collimation, but what a view!  


Now we can say that we got to experience first light on the largest telescope in South America for use by amateurs!  :D  We also took a look at 47 Tucanae, the giant globular cluster.  I wish we could have seen that with this thing collimated!  Oh well, next time :)

We got the car loaded up, bid farewell to Alain, and drove an hour up to Calama, where we would fly out to Santiago.  Then my flight back to the states was later that night, at 8 PM.  The plan was to run around Santiago for a few hours, and then I would head to the airport to catch my flight home.  Due to a miscommunication, John and Beth's flight was the next day, but I was glad to be leaving earlier.  I was ready to head home!

All in all, Chile was an incredible adventure, and I had a great time.  The solar eclipse and the incredible dark, clear skies at the Atacama Lodge were obviously the highlights of the trip!  I had 21 deep sky datasets to process when I got home, plus numerous timelapse videos and single-frame nightscapes.  Not to mention all of the awesome daytime photos of all of our other adventures!  I also got to do a ton of visual observing, which was really rewarding, especially because things weren't just dim fuzzies, but really exciting to look at under those skies!  

I'll definitely have to go back!

[ Update August 5, 2019 ] 

Rho Ophiuchi Complex

I got the Rho Ophiuchi image processed, and HOLY COW did it come out well!

Date: 10 July 2019
Location: Atacama Lodge, San Pedro de Atacama, Chile
Object: Rho Ophiuchi region
Attempt: 7
Camera: Sony a7s, astro-modified (Alain Maury's)
Telescope: Rokinon 135mm f/2.8
Accessories: N/A
Mount: Sky-Watcher Star Adventurer
Guide scope: N/A
Guide camera: N/A
Subframes: 1: 324x30s (2h42m)
2: 58x30s (29m)
Gain/ISO: ISO-1600
Acquisition method: Intervalometer
Stacking program: PixInsight 1.8.6
Post-Processing program: PixInsight 1.8.6
Darks: 0
Biases: 0
Flats: 0
Temperature: 35-45F

Yes, that is only a half-hour of data! :O This image was really exciting to process. I literally got tears in my eyes a bit when it emerged from DynamicBackgroundExtraction. Here's why...


I wasn't sure how much of the nebula was really there with those short exposures, but the Sony a7s is so dang sensitive that I couldn't go much longer without saturating. It turned out to be just right! And I finally got some of that brown color in the dark nebula that I've seen others get but hadn't been able to achieve myself.

The first version of this one didn't come out quite as nice.


The stars got fatter, and the nebula regions weren't as well-defined. The main reason for this was that the focus slipped on the lens not very far into the run, but I tried stacking them all anyway for the sake of SNR. With all of the frames, I had 324x30s, or 2h42m of data. But then I decided to see how it would look with the much smaller number of in-focus frames -- only 58. The result was much better, and the SNR didn't seem to suffer (the lack of light pollution helped, and the apparently low noise of the Sony camera).

Another thing I tried was a new PixInsight process for me -- MaskedStretch. I went looking through Warren Keller's book Inside PixInsight for a section on processing dark nebulae that someone mentioned to me was in there, but wasn't able to find it (at least, not with a couple of quick looks). So I just looked through the section on stretching, and decided to give it a try. It performs a series of stretches, and the end result has the peak of the histogram exactly between the black point and the gray point. Since none of the peak was pushed past these two points, the image was still somewhat dim, so I brought it into CurvesTransformation and brightened it up from there. Then I did a few more steps, and got an end result I was very pleased with!

Here's the steps for the shorter-stack, in-focus version:
- Started with SubframeSelector because no darks/biases:
     - Scale: 12.82 arcsec/px
     - Gain: 0.316 e/ADU
     - Highest-scoring frame: DSC00227 (92.349)
- Debayered
- Registered with StarAlignment
- Stacked with ImageIntegration
     - Combination: Average
     - Normalization: Additive
     - Rejection: Linear Fit clipping
- Cropped with DynamicCrop
- Applied DynamicBackgroundExtraction
- Corrected color with PhotometricColorCalibration
- Stretched with MaskedStretch
- Stretched the rest of the way with CurvesTransformation
- Adjusted curves some more
- Denoised with MultiscaleLinearTransform
- Applied DarkStructureEnhance
- Applied SCNR to help kill leftover green tint
- WoWeEEE

So happy with this one! And a great example of what powerful post-processing does for you.

Milky Way

My random positioning of my 70-300mm lens at 70mm pulled in a nice area of the Milky Way! Included in the scene are M8 Lagoon Nebula and M20 Trifid Nebula, M6 Butterfly Cluster, M7 Ptolemy's Cluster, the Pipe Bowl dark nebula, and more. Also, in one of the frames, I caught a nice meteor! So after processing the image the first time, I took the stacked image, added the single frame with the meteor to it using PixelMath (I'm sure there's a more elegant way to do this), and then applied the same processing steps (mostly). It came out nice! Even though there was a lot of moon in the background in the subframes.
Date: 10 July 2019 
Location: Atacama Lodge, San Pedro de Atacama, Chile 
Object: Milky Way 
Attempt: 12 
Camera: Nikon D5300 
Telescope: Nikon 70-300mm f/4-5.6G @ 70mm, f/4 
Accessories: N/A 
Mount: Sky-Watcher Star Adventurer 
Guide scope: N/A 
Guide camera: N/A 
Subframes: 54x120s 
Gain/ISO: ISO-1600 
Acquisition method: Intervalometer 
Stacking program: PixInsight 1.8.6 
Post-Processing program: PixInsight 1.8.6 
Darks: 58 (44F) 
Biases: 21 (44F) 
Flats: 0 
Temperature: 38-46F (mostly low-mid 40s) 

I tried MaskedStretch on this one too, but it blew out the blue halos around the stars from the slight chromatic aberration of the lens, so I did the stretch myself in HistogramTransformation instead. I still got some blue halos, but not as bad. Then I took it over into Photoshop and used one of Noel Carboni's Astronomy Tools for Photoshop to reduce the blue halos.

Here are all the steps I did:
- Created master bias with ImageIntegration, then Superbias
- Calibrated darks with superbias using ImageCalibration
- Created master dark with ImageIntegration
- Calibrated lights with master dark & superbias using ImageCalibration
- SubframeSelector:
     - Scale: 11.54 arcsec/px
     - Gain: 0.115 e/ADU
- Debayered
- Registered with StarAlignment
- Stacked with ImageIntegration
     - Combination: Average
     - Normalization: Additive
     - Pixel rejection: Linear Fit Clipping
- Added meteor frame to stacked image with PixelMath
     - Tried averaging the two, but it cut the meteor brightness in half (of course)
- Cropped with DynamicCrop
- Applied DynamicBackgroundExtraction
- Denoised with MultiscaleLinearTransform, with luminance mask
- Color corrected with PhotometricColorCalibration
- Tried MaskedStretch, but blue star halos got pretty bad
- Stretched with HistogramTransformation
- Tweaked with CurvesTransformation
- Sharpened with MultiscaleLinearTransform
- Adjusted some more with CurvesTransformation
- Reduce Blue Halos in Photoshop

Sunday, July 28, 2019

#197 - Tuesday, July 9, 2019 - Shooting with an Astro-DSLR

I managed once again to sleep in until 12:45 PM, and thank goodness!  I was starting to feel more adjusted to the altitude, and all three of us felt ready to go do some daytime exploring.  So I copied last night's data off of my memory cards, drank a hearty cup of coffee, and we left at 2:30 PM to go to dome sightseeing.

Our first stop was the Valle de la Luna, or "Valley of the Moon," but they only allow car entry between 8 AM and 1 PM, so we missed our chance.  Try again tomorrow...so instead we set our GPS for one of the sites in the salt flats, Salar de Atacama.  On the highway, we crossed the line of the Tropic of Capricorn!


Salar de Atacama was both the name of the general area, and supposedly a particular lagoon in the salt flats.  Unlike salt flats in other parts of the world, the one here in the Atacama Desert was not really that flat.  Well, the landscape was flat, but the salt formed stalagmites that stuck up out of the ground!  We pulled off to give it a closer look, and it was extremely hard stuff.  The salt chunks were also very sharp -- I was glad I had my hiking boots on with Vibram soles!  It also sounded hollow in places.  John used his Leatherman and some other tools he had in his pockets to bang on the crystalline structures, and with the different tones, he was making some music!  It was very cool and also very strange.


We wound up not finding a particular location or lagoon of Salar de Atacama, so we drove back northward to try Laguna Cejar.  But my phone's GPS said we wouldn't get there till 6:30 -- after sunset.  So we just drove back to the Atacama Lodge instead.  A day of bad luck!  But the drive was gorgeous, so there's that at least.  There were rocks strewn everywhere from volcanic eruptions, and there were some places where the road was washed out due to an earthquake re-routing a stream and launching all kinds of water down the mountain.  We also passed by the entrance to the radio telescope array ALMA, and we could see the workshop from the road.


Once we got back to the lodge, I went and found Alain to ask for help re-polar-aligning my Sky-Watcher Star Adventurer again once it got dark, and to get a status update on the Sky-Watcher AZEQ6 mount I was supposed to be borrowing, but it had quit working.  He said since he couldn't fix it right away, I could instead borrow an astro-modified Sony a7s with a Rokinon 135mm f/2.8 lens!  I was so all over that.  Astro-modified means that a standard DSLR camera has had its spectrum filter removed.  Consumer cameras has a special filter on the camera chip that passes the different wavelengths of visible light (the colors) at different amounts in a way that matches how the human eye responds to color.  This way, images come out looking mostly like how you saw them in real life.  However, the human eye is not particularly sensitive to red, which unfortunately is what a lot of the pretty stuff in the universe emits, especially nebulae.  With the spectrum filter removed, far more red can make it to the camera chip, which increases your signal-to-noise ratio at those wavelengths by quite a bit.  I've seen some amazing images from astro-modified DSLRs.  I've thought about doing it myself, but I think I'll save the money and get a color astro camera instead (such as the ZWO ASI1600MC, the color version of my ASI1600MM Pro) so that I can also have the cooling system.

We had a few issues at the start getting it rolling though.  It had one of those spare battery and memory card compartments attached to it, and for some reason it wasn't liking some of the batteries.  So we finally put just one battery in instead of two, and it seemed happier.  Then, when I was scrolling through the menu options (after having Alain help me change it from French to English), it kept seeming to push buttons on its own!  Finally I called Alain over to take a look, and he just gave me another astro-modified Sony a7s to use instead.  That one seemed to work.  

The Sony a7s is a mirrorless camera, meaning that much like point-and-shoot cameras and video cameras, the viewfinder is electronic.  In order to actually see anything, the image gets stretched quite a bit, so it was far easier to get the camera pointed at what I want, since I could see it on the screen so easily!  It also went up to stupidly high ISO values, like 64,000 (not 6400, 64,000!).  

Now, the Sky-Watcher Star Adventurer actually has two camera-connection screws: one on top of the declination adjustment plate, and one further down on the dovetail.  So what did I do?  Yes that's right.  I put both DSLRs on it - the Sony a7s, and my own Nikon D5300!  Actually, having the D5300 in the lower camera spot, which is toward the middle of the camera-counterweight balance point, helped balance it quite a bit, which was perfect.  The only issue I ran into was that I had to point the cameras carefully, since they would run into each other.  It meant I couldn't quite point both where I wanted to, but I got close enough.  I wound up swapping out the 300mm lens for the 35mm to avoid problems.

Simply glorious -- allllll the imaging!

It was a challenge to focus the Rokinon lens since the focus point was very tight!  But I finally got close, and then pointed the Sony toward Eta Carinae and the Running Chicken Nebula area.  I had to rotate it sideways to avoid seeing a refractor at the front of the shed.  I set the exposure time to 30s because at ISO-1600, one minute was overexposing the image!  The images looked very red due to the lack of spectrum filter, but that will all come out in processing.    Then I pointed the D5300 up to the Rho Ophiuchi region, which took a while to finesse into place so that I could get the most of the dust clouds, but not also get super-bright Jupiter in the scene.

Once that was all set and rolling, I wandered back over to the scopes to see what John and Beth were up to.  John had the 28-inch looking up at Jupiter, which was incredible in the eyepiece!  So bright, and so much detail.  It's so much higher down there than it is up in the US, plus the skies were very clear and steady.  It was breezy out, which made it feel much colder, and the moon was still up and brightening the sky, so we went inside to warm up and wait for it to set.  In the meantime, we worked through some wine we had bought and needed to finish before we left on Thursday.

I went back to the shed later to swap batteries and re-position cameras, including on my Nikon D3100, which I had set up on my mini-tripod to do star trails/timelapse facing south over the robotic scope domes.  

Then it was back to more visual observing -- M25 open cluster, Sculptor/Silver Dollar Galaxy again, NGC 1365, Stephan's Quintet, more Tarantula Nebula, and more 47 Tucanae.  NGC 1365 is a gorgeous barred spiral galaxy in the constellation Fornax, and I could see its shape!  Very very cool.  It's about 60 million lightyears away.  I also tried to find the Bug Nebula, but was unsuccessful.  At some point, I went back over to the shed and changed the Sony to imaging the Large Magellanic Cloud, and the D5300 over to both clouds with its 35mm lens.

Large Magellanic Cloud single frame at f/2, ISO-1600, 30s
Don't worry, the red will process out...

Single frame at f/2.2, ISO-1600, 60s
Caught a meteor in one of the frames!

After over an hour of imaging at those spots, I discovered that I had accidentally left the D5300 set on 10s instead of Bulb from when I was centering the Magellanic Clouds!  It had been imaging for quite a while at that point, but I switched it back to Bulb anyway for the 60s images I had set on the intervalometer.  At 5 AM, I was tired and ready for bed, but since it was still dark until about 6 AM, I left the cameras running this time.  I had started the Sky-Watcher far enough east that I was pretty sure it wouldn't hit the mount before I woke up to shut off the power, and the shed would close at sunrise to protect from the sun (I was pointing south anyway, away from the sun).  Plus, the batteries would die at some point.  So I left it running and went to bed.  

Another fabulous night (and day)!


[ Update July 27, 2019 ] 

Large Magellanic Cloud

Still plowing through datasets...so many left to go!  But each one is a joy!

Here's the Large Magellanic Cloud, from the astro-modified Sony a7s with the Rokinon 135mm f/2 lens, both borrowed from the Atacama Lodge owner, Alain Maury.

Date: 9 July 2019
Location: Atacama Lodge, San Pedro de Atacama, Chile
Object: Large Magellanic Cloud
Attempt: 1
Camera: Sony a7s (Alain Maury's)
Telescope: Rokinon 135mm f/2 lens at f/2
Accessories: N/A
Mount: Sky-Watcher Star Adventurer
Guide scope: N/A
Guide camera: N/A
Subframes: 259x30s (2h9m30s)
Gain/ISO: ISO-1600
Acquisition method: Intervalometer
Stacking program: PixInsight 1.8.6
Post-Processing program: PixInsight 1.8.6
Darks: 0
Biases: 0
Flats: 0
Temperature: 30-32F

😁😁😁😁😁😁😁😁😁😁😁😁
Wowee!  So much detail!  So cool!!
The Large Magellanic Cloud is a dwarf galaxy that is very close to our own -- only 160,000 lightyears away.  It was previously thought to be orbiting the Milky Way galaxy, but we now know from velocity measurements that it's actually just passing through, although it's expected to collide with us in about 2.4 billion years.  It's a disrupted barred spiral galaxy, with the disruption being due to the gravitational interaction between the LMC and the Milky Way.  It's easily visible naked-eye from relatively dark places, and from the darkness of the Atacama Lodge, I could make out structure, especially with averted vision.  It's home to the massive and incredible Tarantula Nebula as well.

Using an astro-modified Sony a7s was fun!  The images were very low-noise -- I didn't have to do any denoising at all while processing these, and I don't even have dark or bias frames for calibration!  The stars were also nice and small, and the detail was just awesome, largely due to the lack of noise I think.  When can I get one of these??

My PixInsight process was as follows:
- Since no darks/biases, started with SubframeSelector
- Scale: 12.82 arcsec/px
- Gain: 0.316 e/ADU (est.)
- Highest-score frame: DSC00136 (86.020)
- Debayered
- Registered with StarAlignment
- Stacked with ImageIntegration
- Combination: Average
- Normalization: Additive
- Pixel rejection: Linear Fit
- Cropped with DynamicCrop
- Applied DynamicBackgroundExtraction
- Color correction with PhotometricColorCalibration
- Applied deconvolution with Deconvolution, with a PSF generated from the image with DynamicPSF, 30 iterations, range_mask - star_mask masking
-  Adjusted curves with CurvesTransformation and ColorSaturation
- Enhanced contrast with HDRMultiscaleTransform

Large and Small Magellanic Clouds together

This one was with my own Nikon D5300!  Like I mentioned, I accidentally took a ton of 10s photos before I realized it and switch to 60s, but together I got about an hour and 45 minutes out of it.  And it came out quite well!

Date: 9 July 2019
Location: Atacama Lodge, San Pedro de Atacama, Chile
Object: Magellanic Clouds
Attempt: 2
Camera: Nikon D5300
Telescope: Nikon 35mm f/1.8G @ f/2.2
Accessories: N/A
Mount: Sky-Watcher Star Adventurer
Guide scope: N/A
Guide camera: N/A
Subframes: 48x60s
   355x10s
   Total: 1h47m10s
Gain/ISO: ISO-1600
Acquisition method: Intervalometer
Stacking program: PixInsight 1.8.6
Post-Processing program: PixInsight 1.8.6
Darks: 72 (30F)
Biases: 20 (28F)
Flats: 0
Temperature: 29-30F

Not much is visible of the Tarantula here, but the globular cluster 47 Tucanae shines bright just beside the SMC.  The stars in my 35mm lens often come out with a pink-magenta-ish tinge, so I had to use a star mask that I enlarged a bit in order to reduce the pink-purple saturation just for the stars.

My PixInsight process:
- Generated master bias & superbias
- Calibrated darks with superbias, integrated with ImageIntegration
- Showed a weird pattern down at the bottom of the frame - calibrated with master bias instead and stacked, looked much better
- Calibrated 10s frames with master bias, and 60s frames with master bias and master dark
- SubframeSelector:
- Scale: 23.07 arcsec/px
- Gain: 0.115 e/ADU
- Highest-scoring 60s frame: DSC_0735 (89.446)
- Debayered
- Registered with StarAlignment
- Stacked with ImageIntegration
- Linear Fit clipping
- Combination: Average
- Normalization: Additive
- Cropped with DynamicCrop
- DynamicBackgroundExtraction
- Denoise with MultiscaleLinearTransform, with lum mask
- Color corrected with PhotometricColorCalibration
- Tried Deconvolution with generated PSF and range_mask-star_mask, but wasn't doing much
- Stretched with HistogramTransformation
- Reduced pink tinge in stars with ColorSaturation and star mask
- Applied HDRMultiscaleTransform, 9 iterations
- Dilated star mask, tried reducing magenta star tone with ColorSaturation again
- Cropped again to cut out telescope shadow and some coma
- Applied ACDNR for some additional noise reduction in brighter areas

Eta Carinae & Friends

This was one of the first datasets I processed after I got home because I was so excited about capturing hydrogen regions with the Sony a7s.  And I was not disappointed!!

Date: 9 July 2019
Location: Atacama Lodge, San Pedro de Atacama, Chile
Object: Eta Carinae Nebula and Running Chicken Nebula
Attempt: 3
Camera: Sony A7s (borrowed)
Telescope: Rokinon 135mm f/2 (borrowed)
Accessories: N/A
Mount: Sky-Watcher Star Adventurer
Guide scope: N/A
Guide camera: N/A
Subframes: 43x30s
Gain/ISO: ISO-800
Acquisition method: Intervalometer
Stacking program: PixInsight 1.8.6
Post-Processing program: PixInsight 1.8.6
Darks: 0
Biases: 0
Flats: 0
Temperature: mid-40s

Just look at all of those stars!!  And they look nice and tight, with tons of detail on the nebulae!  And loads of dark nebula streaks.  I am super excited about this one.

Here's my PixInsight process:
- No darks or biases, so went straight to SubframeSelection:
- Scale: 12.82 arcsec/px
- Gain: 0.158 e/ADU (est.)
- Highest-scoring frame: DSC09400 (94.882)
- Debayered
- Registered with StarAlignment
- Stacked with ImageIntegration
- Combination: Average
- Norm: Average
- Pixel rejection: Linear fit clipping
- Applied DynamicBackgroundExtraction
- Literal tears in my eyes!
- Denoised with MultiscaleLinearTransform
- Didn't necessarily need it, but softened the image a bit in a good way
- Color correction with PhotometricColorCalibration
- Deconvolution with generated PSF from DynamicPSF, range_mask-star_mask, 30 iterations
- Stretched with HistogramTransformation
- Fine-tuned with CurvesTransformation
- Ran DarkStructureEnhance script

Yes, when I ran the DynamicBackgroundExtraction process after carefully adjusting every sample point so as not to be over a star or nebulosity, by jaw hit the floor.  It was so beautiful!


DynamicBackgroundExtraction forever!!

I will write a blog post on my new workflow and provide a step-by-step.  I haven't had time -- it takes a ton of time to do that!  But I will, I promise!

[ Update August 17, 2019 ] 

Still working through my Chile data...very excited about this image of the Milky Way with the Sony a7s and Rokinon 135mm lens!  Got some nice detail in the twisting dust clouds, and some nice color.

Date: 9 July 2019
Location: Atacama Lodge, San Pedro de Atacama, Chile
Object: Milky Way (Sagittarius)
Attempt: 10
Camera: Sony a7s (ILCE-7S) (astro-modified)
Telescope: Rokinon 135mm f/2 @ f/2
Accessories: N/A
Mount: Sky-Watcher Star Adventurer
Guide scope: N/A
Guide camera: N/A
Subframes: 236x30s  (1h58m)
Gain/ISO: ISO-1600
Acquisition method: Intervalometer
Stacking program: PixInsight 1.8.6
Post-Processing program: PixInsight 1.8.6
Darks: 0
Biases: 0
Flats: 0
Temperature: 40-45F ish

Here, we are looking at several nebulae, star clusters, and a ton of dark molecular dust in the core of the Milky Way. The big pinkish nebula right of center is M8, the Lagoon Nebula, with M20, the Trifid Nebula, lying just below and to the right. Just to the right of M20 is open cluster M21. The large open cluster in the lower right of the image is M23, which contains about 150 stars in an area 20 lightyears wide. Close inspection of the image reveals a lot of intricate detail in the twisting dust clouds above and below the main dark band of the galactic center.

PixInsight process:
- No darks/biases, so started with SubframeSelector:
- Scale: 12.82 arcsec/px
- Gain: 0.316 e/ADU (est.)
- Highest-scoring frame: DSC09658 (85.816)
- Debayered
- Registered with StarAlignment
- Stacked with ImageIntegration
- Combination: Average
- Normalization: Additive
- Pixel rejection: Linear Fit clipping
- Tried denoising with MultiscaleLinearTransform, but didn't really need it, and killed the 
dimmer stars
- Color corrected with PhotometricColorCalibration
- Same as 1, but I did Deconvolution with range-star mask, PSF from DynamicPSF, 15 iterations
- Stretched with MaskedStretch
- Adjusted with CurvesTransformation
- Cropped to center portion that I liked more
- More CurvesTransformation
- DarkStructureEnhance

So much fun :D




Friday, July 26, 2019

#196 - Monday, July 8, 2019 - High-Tech Star Hopping

After hitting the sack at 5:45 AM, I managed to sleep until 12:45 PM, thanks to my sleeping mask!  It was so bright though that I could see light through it still :/  My travel companions John & Beth saved the shower for me this time, so I had some hot water and water pressure, which made for a much more enjoyable experience than the day before!

We just hung around the lodge again all afternoon, and I worked on organizing data.  We then decided to drive over to this beautiful lookout spot that overlooked a jagged, rocky miniature canyon only a few miles from us, where people gathered every night to watch the sun set over the rocks and the Andes mountains in the background.


I took a bunch of images to make a timelapse, which I haven't made yet, but I'll add it here once I do!  It was beautiful to watch; the shadow of the mountains on the other side slowly creeped across the landscape, the sky above the Andes was orange, and the mountains themselves a peach-pink.  A dark band appeared above the mountains later on, and then the sky faded to dark blue.  

After sunset, we drove back to the lodge, made hamburgers on the stove for dinner, and then around 7:45 PM, I went to set up my Nikon D5300 on my Sky-Watcher Star Adventurer mount with my 70-300mm lens.  Since Alain, the Atacama Lodge owner, had helped me polar align it the night before, and I had weighted down the tripod with some heavy stuff I found on the floor of the roll-off shed (a counterweight and a few other random items), it should track pretty well even at 300mm!  I pointed it at the Eta Carinae Nebula and took some test shots, which showed that I could go as long as 90s without streaking.  Not bad for 300mm unguided!  My next project for the Star Adventurer is to get a guidescope attached to it.  I have some CCTV lenses and a C-mount to T-thread converter; now I just need to figure out a way to attach it to the mount.  Anyway, I got a good amount of detail to show up at 90s -- can't wait to stack it!

Eta Carinae Nebula, single 90s frame, Nikon D5300, 300mm, f/5.6, ISO-1600

It was nice and warm out that evening -- my digital thermometer in the roll-off shed said 46F, which is downright balmy after the 32F the previous two nights!  So I went over to the 20-inch-ish Dob near our lodge and looked for a bunch of stuff with John and Beth.  The large French were having some big fancy dinner in one of the other lodges, so we had it to ourselves.

First, we viewed the Eta Carinae Nebula with the OIII filter, which Beth had been absorbing all evening.  There is so much to see!  It is seriously impressive at the eyepiece.  As was massive globular cluster Omega Centauri of course, sporting hundreds if not thousands of resolvable stars under the dark, steady skies.  It's thought to contain as many as 10 million stars, making it the king of globular clusters in the Milky Way galaxy.  Many of its stars are 12 billion years old!  These millions of stars are packed into an area only 150 lightyears across, which from Earth appears nearly as large as the full Moon on the sky.  It's estimated that the average distance between stars is only one-tenth of a lightyear!  Now imagine living on a planet with that many bright stars in the sky.

I wanted to see Centaurus A next.  It's a big enough Dob that I couldn't quite figure out how to star-hop, especially since many of the stars were unfamiliar, and I couldn't tell which was which between my phone app map and the eyepiece.  So instead, I brought a little technology to the task!  I looked up Centaurus A's current altitude and azimuth in my SkySafari app (there's a free version known as SkyPortal, FYI).  I then used my phone's compass to point the scope in the right direction, and a level indicator in an app I use all the time called GPS Status to get the elevation set close.  Then I fished around for a bit, looking for star patterns that matched up with SkySafari, and boom, there it was!  It wasn't terribly bright, but you could definitely make out the hamburger shape.  It's quite large on the sky, so it's rather diffuse in the eyepiece.  I found an object in a Dob all by myself, woo hoo!

We swung by the nearby Southern Pleiades, a gorgeous open cluster that you basically trip over anytime you're looking from something around Eta Carinae, and then hopped over to Saturn.  It was incredibly sharp in the high-altitude, steady desert air, making the Cassini division very easy to see, in addition to several cloud bands.  And it was so dark that I saw more moons than I had ever seen before!  I checked their positions in SkySafari.  Previously, I'd only seen Titan and I think Tethys once or twice, but clear as day, there were Rhea, Dione, Enceladus, and Tethys!  Titan was pretty far outside the view in the eyepiece.  So cool!

We checked out the open cluster in the Coalsack Nebula, and then I went hunting for the Running Chicken Nebula, but could only see the open cluster Lambda Centauri and no nebulsoity.  Darn!

Photo by John - light is from the moon

Throughout the night, I ran around taking pictures of stuff with the sky in the background using my 35mm lens on my other DSLR, my Nikon D3100.


After a snack back in the lodge, I went back over to my Star Adventurer to change my D5300 over to somewhere in the vicinity of M8 & M20, the Lagoon and Trifid Nebulae.  They were up at zenith, which would make for some very clear shots!  It also made it hard to aim the camera.  While I was adjusting my headlamp out of the way, it snapped off, and the pieces went flying.  So I fumbled around for a few minutes until I found all the batteries and plastic, snapped it back together, and went back to finding M8 & M20.  I finally found it, but then I worked on getting it centered, which took another several minutes!  Finally got it where I wanted it.  Mostly.  Or I just gave up.  I really wanted to get the cloud below M8, which I have tried to capture before but haven't succeeded.  I can just barely see it in the subframes, so here's hoping it comes out in stacking!  It probably will, stacking is magic.

M8 & M20, Single raw 90s frame, Nikon D5300, 300mm, f/5.6, ISO-1600

After another snack around 11:30 PM (staying up all night is a lot of work!), I went over to the big telescopes, since the tour groups had cleared out.  I tried my hand again at finding stuff, and found quite a few things in the 28-inch and 24-inch Dobs!  A few from the French group were there, and they pulled up the Lagoon Nebula through the 24-inch, and helped me find the Dumbbell Nebula (way harder than it should have been!).  Then I spent quite a bit of time hunting down the Veil Nebula up in Cygnus, and I did finally find the Western Veil.  The OIII filter had disappeared somewhere, so I didn't get to see it with that (which would have been awesome), but it was really cool to see this giant, gray whispy thing there in the eyepiece!  I went looking for the nearby Eastern Veil as well, but didn't quite find it.  I did see some other nebulosity though, potentially some of the Pickering region.  I got to see that through a 16-inch Dob at the Green Bank Star Quest in 2017 when it was way up at zenith, which was quite amazing to see, especially with an OIII filter.  

One really cool object that I am super proud that I found (with my high-tech technique!) is the Skull Nebula, NGC 246.  It's a planetary nebula in Cetus, and lies about 1600 lightyears away.  It's about twice the size of the Ring Nebula on the sky, making it somewhat diffuse and difficult to spot at higher magnifications.  It really popped out against the dark sky though as a fuzzy gray circle.  With an OIII filter, it really changed character -- I could see structure in it!  Like it had large lumps.  It doesn't climb very high in the northern sky, unfortunately.  It was super cool to see!  And I found it by myself!

While I was doing that, some of the French folks found a cluster of galaxies that I didn't quite catch the name of.  It was a really pretty grouping.  One thing that was interesting is that under the murky skies at home, adding more magnification to something usually fuzzes it out.  But the seeing was so good here that adding more magnification actually made it sharper!  My brain was too fuzzed out to remember what constellation we were looking in though, so darn.

Finally, the Large Magellanic Cloud was up high enough to image at about 3:30 AM, so I moved my D5300 over to that.  But I must have moved the tripod or mount or something a little because I was getting streaky stars!  So I gave up on that and went back to the telescopes.  Since the LMC was up, that meant it was Tarantula Time!  We got the 28-inch Dob pointed at it, and gasped in amazement.  It was beyond belief!  So much detail and blue-green color.  Truly breathtaking!  We kept taking turns looking at it.

Beth looking at the Tarantula Nebula in the 28-inch.

Since the Milky Way was now much lower in the sky, it was a great opportunity to take some epic-level images with scopes and stuff in the foreground.
Proooooobably the most epic selfie I've ever taken.  Just sayin'.
Nikon D3100, 35mm, f/1.8, 10s, ISO-3200

3-panel mosaic of the 28-inch Dob
Nikon D3100, 35mm, f/1.8, 10s, ISO-3200

I took one last look at the Tarantula Nebula, and then shut everything down and went to bed at about 5:30 AM.  Another truly, truly excellent night!

[ Update July 29, 2019 ] 

Processing the Eta Carinae Nebula

So 90 seconds proved to be a little too long at 300mm, unfortunately.  Either that, or the polar alignment got knocked out earlier than I thought.  In either case, I had to dump a lot of frames, and the frames I kept were barely marginal in the star shape.  But I processed it anyway, and it's not too bad of a result.  Dark skies buy you a lot.

Date: 8 July 2019
Location: Atacama Lodge, San Pedro de Atacama, Chile
Object: Eta Carinae
Attempt: 2
Camera: Nikon D5300
Telescope: Nikon 70-300mm f/4-5.6 G at 300mm, f/5.6
Accessories: N/A
Mount: Sky-Watcher Star Adventurer
Guide scope: N/A
Guide camera: N/A
Subframes: 48x90s (1h12m)
Gain/ISO: ISO-1600
Acquisition program: Intervalometer
Stacking program: PixInsight 1.8.6
Post-Processing program: PixInsight 1.8.6
Darks: 0
Biases: 20
Flats: 0
Temperature: 38-41F

This one wound up with an unusually green background somehow (airglow?) even after I ran the color correction, so I just tweaked the histogram at the end of stretching to kill the green background a bit more.  It worked nicely, and I was able to adjust the red and the blue as well so that the colors looked more natural.  I wound up with some blue halos from this lens, which I was able to reduce using Noel Carboni's Astronomy Tools for Photoshop when de-saturating blue with a star mask in PixInsight didn't really do anything.  Of course, the algorithm also killed the blue in the nebula a bit, which I had to add back using the Curves tool in Photoshop, which added back some of the blue halos.  Oh well!

Here's the PixInsight process:
- Created master bias with ImageIntegration
- Generated superbias from master bias
- Calibrated lights with superbias
- SubframeSelector:
- Scale: 2.69 arcsec/px
- Gain: 0.115 e/ADU
- Highest-scoring frame: DSC_0010 (90.716)
- Debayered
- Registered with StarAlignment
- Stacked with ImageIntegration
- Combination: Average
- Normalization: Additive
- Pixel rejection: Linear Fit Clipping
- Cropped with DynamicCrop
- Applied DynamicBackgroundExtraction
- Denoised with MultiscaleLinearTransform
- Corrected color with PhotometricColorCalibration
- Tried Deconvolution, but didn't work very well
- Stretched with HistogramTransformation
- Eroded stars with MorphologicalTransformation
- Morphological Selection, 0.30
- Undid the erosion; caused some weirdness
- Adjusted with CurvesTransformation
- Reduced blue halos in Photoshop

It's a gorgeous nebula nonetheless!  Still have several more datasets to process.  Should I be packing for my upcoming move?  Yes...Am I? No...processing astrophotography is more fun than organizing my office!