#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

So cool! :D

Next post: #199 - Tuesday, July 23, 2019 - New Scope!

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

Table of Contents

#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

See on AstroBin

😁😁😁😁😁😁😁😁😁😁😁😁

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

See on AstroBin

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

[ Update August 31, 2019 ] 

Almost through all of my Chile data!  Tons of great widefield Milky Way shots.  Here's another one!

Date: 9 July 2019

Location: Atacama Lodge, San Pedro de Atacama, Chile

Object: Milky Way

Attempt: 11

Camera: Nikon D5300

Telescope: Nikon 35mm f/1.8G @ f/1.8

Accessories: N/A

Mount: Sky-Watcher Star Adventurer

Guide scope: N/A

Guide camera: N/A

Subframes: 171x60s (2h51m)

Gain/ISO: ISO-1600

Acquisition method: Intervalometer

Stacking program: PixInsight 1.8.6

Post-Processing program: PixInsight 1.8.6

Darks: 46F: 56

   40F: 40

   34F: 20

Biases: 46F: 20

40F: 20 (actually 42F)

34F: 0

Flats: 0

Temperature: 35-47F

I learned something interesting in processing this dataset.  The first half of the night had a pretty bright moon (hence the large temperature difference through the dataset), so I stacked the image twice: once with all of the images (that made it through quality check), and once with just the ones without moonlight.  There was actually not much difference at the end of the day between the two datasets!  I had to do some extra gradient removal on the moonlit one, but it wasn't too hard, and I actually liked the result better.  Here's the one without any moonlit frames (which amounted to be 70x60s):

The blue gradient is still there (I didn't try to remove it in this one), and I prefer the look of the first image.  (The main reason the two look different is just slightly different processing -- I didn't save out every process to exactly repeat all of the steps).  So that is a really interesting result -- I can do just about as well with moonlight as without!  For bright objects like the Milky Way, at least.  Processing can do a lot for you if done well.

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

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

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#185 - Tuesday, April 30, 2019 - A Stellar All-Nigher: Texas Star Party Night #3

After getting to bed around 2:30 AM on Monday night, I slept in till 10 AM again, showered, and scarfed down a lunch of pasta, meatballs, and veggies.  We had an important date to make: a trip to the McDonald Observatory!  This would be my third visit, and even though it was a technical tour sure to go over my parent's heads, it's fun for anyone to stand underneath a big scientific instrument.

It was Science Fiction day, so my dad chose an appropriate T-shirt.

He is indeed 6'5", in case you were wondering.

My mom and aunt had gotten NASA t-shirts, so I wore mine too, wanting to match.  We took a group photo in front of the building housing the 82", the first scope built there.

The view from up top was awesome.

We got tours of the 107" Harlan J. Smith telescope and the 300" Hobby-Eberly telescope.  My family was quite impressed!

The sky was clear all day, and the forecast looked very promising.  After dinner, it was time to rock and roll.

I trotted down to the lower field after dinner and pulled the covers off my scopes, woke them up from hibernation, connected the computers, and began cooling the cameras.  While I waited, I ran up to the upper field to set up my Nikon D3100 on my other tripod to do what I have been wanting to do for a while now: an all-night, sunset-to-sunrise timelapse.  I set it up at the top of the upper field, set the exposure time to 15s, focused, and let it roll.  I had it connected to AC power, so I wouldn't have to come back and touch it all night.

As darkness fell, I checked focus on the Takahashi on my own Celestron AVX mount (with my uncle's SBIG STF-8300M camera), pointed it at M101, and let it roll on collecting LRGB frames.  Once that was rolling, I moved my attention over to my Borg 76ED on the borrowed Celestron AVX from Derek to try polar aligning it and aligning it again.  That went well this time.  Then I realized I had a problem: I wasn't going to be able to guide it.  The guide scope I normally use, my Orion 50mm, was over on the Tak happily guiding away, and my other Orion 50mm had a different kind of T-shaped adapter that I bought accidentally a while back.  So I was going to have to choose a target that I could do with short exposures.  I settled on M63, the Sunflower Galaxy, and after getting it centered, I set up the sequence for LRGB frames, and let it roll.

While those images were rolling, I walked my family through the "Rising Star" Texas Star Party observing list, which included identifying constellations such as Leo and Corvus, finding the North Star, and seeing globular clusters Omega Centauri and M13.  The whole list is designed to be done naked-eye, but I showed them some of the objects in the telescope as well when I set up my 8-inch SCT later in the night.  We got a good ways through the list.  While facing east looking at Hercules after midnight for M13, my aunt asked what the backwards-C-shaped grouping of stars above Hercules was.  I told her congrats, you've discovered Corona Borealis, Crown of the North!  I was really excited that they were taking such interest in the sky.

After the Milky Way was up, I decided to go ahead and change targets on the Tak to something in that vicinity.  I have attempted the Elephant Trunk Nebula, IC 1396, a few times before, but it's very large and I could never get quite enough signal on it.  I decided to try it in narrowband.  Now, if you punch IC 1396 into the Celestron hand controller, it won't quite have the elephant trunk part of that larger nebula centered, so instead I flipped over to Cartes du Ciel on my tablet and downloaded the DSS (Digital Sky Survey) image for the area, and used that image to choose the centering point.  Then I used CdC to slew the telescope to that spot.  Then in Sequence Generator Pro, I put it on the Frame & Focus mode taking 1-second exposures, lined up where the stars were with relation to the nebula according to the SkySafari app, and centered where I thought the nebula was as best I could.  I flipped over to the Ha filter, and saw that it was out of focus!  I thought that Astronomik filters were supposed to be parfocal with each other, but apparently this wasn't quite the case.  So I slewed over to a nearby bright star, threw on the Bahtinov mask, and got it focused.  To see how that compared to the L channel, I changed to that filter, and it still looked in focus!  So I think that they are close to each other, but a small offset in focus in the L channel can show up as a bigger offset in focus in the Ha channel or something.  I would have to remember to focus in Ha and not L if I was planning on doing narrowband.

Anyway, I got back onto the Elephant Trunk, took a 5-minute test exposure, and...nothing!

Guess I need a longer exposure?  Or maybe I wasn't quite as on target as I thought.  I checked using astrometry.net, and I was indeed pretty close:

On the Results page on astrometry.net, there's a link for seeing your image aligned in Worldwide Telescope.  I reduced the image opacity on my overlaid image to see the imagery underneath.  You can see the Elephant Trunk portion on the right half of the image.

Instead, I moved over to M16 Eagle Nebula to see how that would fare.  Quite well, as it turned out!  And with a 10-minute subframe, my stars were still round!  I couldn't believe it!

It looks like my fix of moving the gears closer together in both axes on my AVX was working beautifully to virtually eliminate backlash.  I wanted to try 15 minute subs, but still wanted to get enough subframes for good signal-to-noise ratio, so I decided to push that experiment off to another night when we have the Milky Way for longer.  I got about seven subframes that night.  After looking at the forecast, I decided I didn't want to take my changes on not getting some complete datasets, so I went ahead and went back over to M101 to get the blue frames that I didn't get previously.

Back over on Derek's AVX with my Borg and ZWO ASI1600MM Pro, the periodic tracking error was pretty bad.  Even at 20s, my stars looked pretty wonky.

But I decided to press anyway, and took a bunch of 30s frames in LRGB.  It's so nice having an electronic filter wheel now, I can just set the sequence in Sequence Generator Pro and it will chug along, changing filters for me.

Once the Milky Way was appreciably high, I switched over to the Dumbbell Nebula, and ran 30s LRGB on that.

I also set up my Nikon D5300 on my Sky-Watcher Star Adventurer.  I had to traverse quite a ways from where my rig was to find another power outlet -- the ranch set up a new power pedestal this year down in the lower field, but were still using the extra-long power cables with outlet boxes every so many feet, which were originally made to run from the RV area onto the field.  This meant that the first box was quite a ways down the cable from the power pedestal, so I had to travel about halfway down the field to find an open one!  Luckily, I've gotten pretty good at finding my way around in the dark out there.  It is so dark I think nearly all of the ambient light comes from the stars.  There is some light pollution in the north, however, from the oil fields.  Anyway, I put the 35mm f/1.8 lens I was borrowing from fellow club member Paul on my Nikon D5300 and took more Rho Ophiuchi region frames.

Single 3-minute subframe, ISO-1600.  The high background is a result of airglow.

Sometime during all of this, I set up my 8-inch Schmidt-Cassegrain on its NexStar SE mount that I brought for visual observing.  After my family went to bed around 2 AM, I needed something to do, so I worked on the "Smoke and Mirrors" Texas Star Party 2019 regular observing list.  It was made up of dark nebulae and galaxy pairs.  Some of the galaxies I couldn't quite snag, but one extremely cool thing I saw was Barnard 86, "Herschel's Hole in the Heavens."  It's a very dark blotch inside of dense open cluster NGC 6520 in Sagittarius, set against the thick background of Milky Way disk stars.  It really does look like a hole in the sky!  It was extremely cool.  I added it to my imaging list for next year's TSP.

After an overall pretty successful night, I shut everything down and covered the scopes as pre-dawn light began to fill the sky.  An extremely slender crescent moon rose above the break in the hills to the east.  As I made my way up to the upper field to grab my Nikon D3100 I had set up there for the all-night timelapse, I saw Venus crest the hills, chasing the moon.  I climbed into bed at 6:30 AM, before the sun rose, but with a nearly fully-lit sky.  An excellent night!

Here's the timelapse video:

I accidentally set the ISO to 1600 instead of something higher like 6400, since I normally image at 1600 on my DSLRs.  So the Milky Way doesn't really come through, unfortunately.  It's still a fun video though.  Some of the bright flashes you see in the video are the now-dimmer Iridium flares, airplanes, and other satellites.  I did catch the edges of two meteors, though!

[ Update May 11, 2019 ] 

Got the Dumbbell Nebula image processed today!

Date: 30 April 2019

Location: Texas Star Party, Fort Davis, TX

Object: M27 Dumbbell Nebula

Attempt: 12

Camera: ZWO ASI1600MM Pro

Telescope: Borg 76ED

Accessories: Starlight Xpress filter wheel, Astronomik LRGB Type 2c 2-inch filters

Mount: Celestron AVX (club member Derek's)

Guide scope: N/A

Guide camera: N/A

Subframes: L: 76x30s

   R: 78x30s

   G: 34x30s

   B: 34x30s

   Total: 1h51m30s

Gain/ISO: 139

Stacking program: PixInsight 1.8.6

Post-Processing program: PixInsight 1.8.6

Darks: 20

Biases: 0

Flats: 0

Temperature: -20C

Not bad considering the lack of ability to guide!  I really love my ZWO camera.  It's so sensitive.  I got some nice structure on the nebula, despite my messy stars.  Deconvolution helped bring that out a bit.

Here are the processing steps:
- Stacked biases and created superbias
- Calibrated darks with superbias
- Calibrated lights with darks and superbias
- So yeah there is definitely something wrong with the biases - calibrating with just darks
- Calibrated lights with just darks
- SubframeSelector
- 1.567 arcsec/px
- 0.059 e/ADU
- L frame 34-4 has the highest score (93.8)
- Registered to L frame 34-4 using StarAlignment
- Stacked with ImageIntegration, Linear Fit Clipping for all
- Applied DynamicBackgroundExtraction to each LRGB channel
- Applied LinearFit to RGB channels with L as reference
- Combined RGB channels with ChannelCombination
- Applied MultiscaleLinearTransform to RGB image for denoising, without mask
- Applied MultiscaleLinearTransform to L image for denoising, with mask (zero-clipped)
- Created model PSF (point spread function) using DynamicPSF for deconvolution process
- Created range mask from stretched L image
- Created star mask from unstretched L image
- Applied Deconvolution to L image
- Stretched L and RGB using HistogramTransformation
- Combined L and RGB channels using LRGBCombination
- Applied PhotometricColorCalibration
- Adjusted curves with CurvesTransformation
- Tried to kill greenish background with ColorSaturation
- Brought in Photoshop for blue halo removal using Noel Carboni tools
- Brought back into PI for one more DBE to flatten remaining gradients

[Update May 24, 2019]

All righty, here is the completed Rho Ophiuchi complex image!

Date: 28 April 2019 & 30 April 2019

Location: Texas Star Party, Fort Davis, TX

Object: Rho Ophiuchi region

Attempt: 6

Camera: Nikon D5300

Telescope: Nikon Nikkor AF-S 35mm f/1.8 lens at f/2 (borrowed)

Accessories: N/A

Mount: Sky-Watcher Star Adventurer

Guide scope: N/A

Guide camera: N/A

Subframes: 1: 86x180s (4h18m)

   2: 95x180s (4h45m)

Gain/ISO: ISO-1600

Stacking program: 1: PixInsight 1.8.6

2: DeepSkyStacker 3.3.2

Post-Processing program: PixInsight 1.8.6 and Photoshop CC 2019 

Darks: 56 @ 40F, 22 @ 52F

Biases: 29 @ 40F, 20 @ 50F

Flats: N/A

Temperature: 28 Apr:  52-53F

30 Apr: 38-46F

So I tried processing it just in PixInsight first, but it didn't come out quite the way I wanted.  Back when I was using DeepSkyStacker, if I stacked this kind of wide-field Milky Way image using settings like I would for a deep sky object, it always came out looking overdone or something like that.  Like too much was brought out.

Processed with PixInsight alone -- not super happy

So I brushed the dust off of DeepSkyStacker and stacked these images there using the Auto-Adaptive Weighted Average stacking algorithm that seems to work quite well on these widefields.  I saved the 32-bit TIFF out of DSS and brought it into PixInsight to process, and was much happier with the result.  I ended up having to use the method in Light Vortex Astronomy's tutorial on using the Hubble palette on narrowband images to remove the pink tinge from the stars, but it worked pretty well!

So here's the process:

- Stacked in DeepSkyStacker 3.3.2, Auto-adaptive weighted average

- Didn't apply changes, saved as 32-bit TIFF, brought into PI

- Crop

- Applied DynamicBackgroundExtraction

- Applied PhotometricColorCalibration for color calibration

- Denoised with MultiscaleLinearTransform, with stretched luminance mask

- Stretched with HistogramTransformation

- Created magenta star mask with ColorMask utility, dilated stars in mask with MorphologicalTransform, then desaturated magenta in ColorSaturation

- Adjusted curves with CurvesTransformation

- Created regular star mask and desaturated red - still not quite killing it

- Applied HDRMultiscaleTransform to increase contrast

- Another round of DynamicBackgroundExtraction

- DarkStructureEnhance script

It turned out quite nice!

If you're interested, I put this image on a bunch of products on Zazzle, from canvas prints to phone cases to throw pillows!  Click here for all of them.  Most items are customizable -- you can change the size (and thus cost) of prints, or change which phone the phone case is for, etc.  Also Zazzle has "faux canvas prints" now that are way cheaper than the real canvas prints!

[ Update June 9, 2019 ] 

While it didn't turn out quite as awesome as I'd hoped, I still got better detail than my first attempt with my DSLR back at the 2017 Texas Star Party.  

Date: 30 April 2019

Location: Texas Star Party, Fort Davis, TX

Object: M63 Sunflower Galaxy

Attempt: 2

Camera: ZWO ASI1600MM Pro

Telescope: Borg 76ED

Accessories: Starlight Xpress filter wheel, Astronomik LRGB Type 2c 2-inch filters

Mount: Celestron AVX (friend Derek's)

Guide scope: N/A

Guide camera: N/A

Subframes: L: 47x30s

   R: 40x30s

   G: 39x30s

   B: 42x30s 

   Total: 1h24m

Gain/ISO: 139

Stacking program: PixInsight 1.8.6

Post-Processing program: PixInsight 1.8.6, Photoshop CC 2019

Darks: 20

Biases: 0

Flats: 0

Temperature: -20C

Date: 22 May 2017

Location: Prude Ranch, TX - Texas Star Party

Object: M63 Sunflower Galaxy

Camera: Nikon D5300

Telescope: Celestron C11

Accessories: f/6.3 focal reducer

Mount: Celestron CGE Pro

Guide scope: Orion ST-80

Guide camera: QHY5

Subframes: 18x300s (1h30m)

Gain/ISO: ISO-1600

Stacking program: DeepSkyStacker 3.3.2

Darks: 24

Biases: 20

Flats: 20

Temperature: 47-59 F

Well, then again, maybe the detail isn't that much better! 😂 

This dataset had some difficulty, mainly in the fact that my stars weren't very round at all, which was a result of two factors.  One was the fact that I wasn't able to guide that night since I didn't have another copy of the right kind of attachment for my other 50mm guide scope.  The other was a result of my field flattener being a little off-kilter from my scope, which made the stars a little more seagull-shaped.

While I was processing, I got some really weird effects after I registered my frames.  I forgot to save a screenshot, but basically I was getting a bright cross-hatch pattern over top of each frame when I auto-stretched, but only the color data, not the luminance.  Now, the reference frame for registration was luminance, but StarAlignment  is just aligning the frames, not applying any effects.  At first, I thought maybe my histogram peak was so low that I was dipping well into the sensor noise, so I went ahead and stacked the frames and combined, but it was bad.  

So I went back a step and aligned the frames from before I applied the score from SubframeSelection in case that was doing something, but it was the same.  So I went back one more step and registered and stacked the light frames without calibrating them with darks and biases -- and that worked.  So this image ended up a little noisy in the color because I couldn't calibrate them for some reason.  Mind you, the luminance frames were just fine, and they used the same calibration!

After that, everything went pretty swimmingly.  I did have to bring it over into Photoshop to use Noel Carboni's Astronomy Tools to kill the little blue halos -- my Borg is supposed to be apochromatic, but it's not quite there.  (The blue halos don't show with my DSLR, but my ZWO is very sensitive and they do show a bit!)

So here's the whole process.

- Created master dark with ImageIntegration

- Skipped bias because still haven't taken new -20C biases (causing problems in previous images)

- Calibrated lights with dark using ImageCalibration

- SubframeSelector on all frames to produce weights

- Scale: 1.567 arcsec/px

- Gain: 0.059 e/ADU, 12-bit

- Noted highest-scoring frame

- Registered frames with StarAlignment to highest-scoring L frame

- Auto-stretch showed weird checkerboard pattern on RGB, not L though

- Stacked with ImageIntegration

- Cropped with DynamicCrop

- Applied DynamicBackgroundExtraction to each channel

- Applied LinearFit to RGB channels with L as reference

- Combined RGB channels with ChannelCombination

- Yeah the hatching is bad

- Tried registering calibrated (but not approved) frames - still bad

- Tried registering non-calibrated lights - hatching gone, so something wrong with darks (

(but only with RGB??)

- Deleting previously-registered frames and replacing with non-calibrated RGB frames

- Stacked non-calibrated frames - didn't want to re-run SubframeSelector, so used NoiseEvaluation instead as the Weight

- Cropped, DBE, LinearFit, combined RGB channels

- Applied MultiscaleLinearTransform to RGB and L, with extracted luminance mask

- Color corrected RGB with PhotometricColorCalibration

- Created sampled PSF (point spread function) from L frame for deconvolution

- Applied Deconvolution to L, 20 iterations, with range_mask-star_mask for mask

- Stretched L and RGB with HistogramTransformation

- Denoised RGB with MultiscaleLinearTransform, with extracted luminance mask

- Combined L and RGB images with LRGBCombination

- Applied another round of DynamicBackgroundExtraction

- Applied HDRMultiscaleTransform, with range mask

- Denoised with MultiscaleLinearTransform again, with extracted luminance mask

- Adjusted with CurvesTransformation

- Imported into Photoshop, ran Carboni's reduce small blue/violet halos routine

- Cropped with DynamicCrop

- Adjusted histogram to reduce background a bit with HistogramTransformation

And there you have it!

Next post: #186 - Wednesday, May 1, 2019 - The Long Night: Texas Star Party Night #4

Previous post: #184 - Monday, April 29, 2019 - At Last, Some Success: Texas Star Party Night #2

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