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??
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!
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.
[ 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
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.
