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!
[ Update August 30, 2019 ]
I actually processed this one a month ago, but forgot to write it up in here! Despite the subframes not being terribly exciting, this one came our rather nice.
Date: 8 July 2019
Location: Atacama Lodge, San Pedro de Atacama, Chile
Object: M8 Lagoon Nebula & M20 Trifid Nebula
Attempt: 3
Camera: Nikon D5300
Telescope: Nikon 70-300mm f/4-5.6G @ 300mm, f/5.6
Accessories: N/A
Mount: Sky-Watcvher Star Adventurer
Guide scope: N/A
Guide camera: N/A
Subframes: 9x90s (13m30s)
Gain/ISO: ISO-1600
Acquisition method: Intervalometer
Stacking program: PixInsight 1.8.6
Post-Processing program: PixInsight 1.8.6
Darks: 0
Biases: 20 (28F)
Flats: 0
Temperature: 29-36F
That 70-300mm lens does have a bit of chromatic aberration, which causes the blue halos around the stars. I have a Photoshop tool from the Noel Carboni Astronomy Tools for Photoshop kit that is great at removing those, but when they're in the middle of a big bright nebula (as is the case with M8), then holes are left where the halos once were, and the effect is worse. I also tried to kill them in PixInsight using a star mask and desaturating blue, but it didn't help much, unfortunately.
Here's the whole process:
- Calibrated lights with previously-made superbias
- SubframeSelector
- Scale: 2.69 arcsec/px
- Gain: 0.115 e/ADU
- Highest-scoring frame: DSC_0225 (95.216)
- Debayered
- Stacked with ImageIntegration
- Combination: Average
- Normalization: Additive
- Pixel rejection: Winsorized Sigma Clipping
- Cropped with DynamicCrop
- Applied DynamicBackgroundExtraction
- Denoised with MultiscaleLinearTransform
- Color corrected with PhotometricColorCalibration
- Tried Deconvolution with DynamicPSF and range_mask-star_mask, but at a number of iterations low enough to not cause weirdness, effect is negligible
- Applied MaskedStretch, but stars got super blue; undid
- Stretched with HistogramTransformation instead
- Applied CurvesTransformation
- Tried to kill halos in PixInsight and Photoshop, but didn't help or caused problems
- Applied HDRMultiscaleTransform
- Tweaked with CurvesTransformation
- Denoised with ACDNR
- Sharpened with MultiscaleLinearTransform
- Applied DarkStructureEnhance
- Increased saturation of nebulae using range_mask and Saturation in CurvesTransformation
M8, the Lagoon Nebula, is the one at the center, and M20, the Trifid Nebula, is toward the upper left. Also making an appearance is open cluster M21, beside M20. There's a sort of bumpy nebula below M8 that I have tried to capture with M8 before unsuccessfully that I finally got some of this time! M8 & M20 are near the heart of the Milky Way, so there's a lot of glowing stars and gas, along with dark dust, sharing the field as well. I had to ditch most of the images in this dataset because of polar alignment issues, but the nine I got to keep made a decent image despite that (thank you dark skies!)
The Lagoon Nebula is a large star-forming region somewhere between 4000-6000 lightyears from Earth. It's enormous, spanning 110 lighyears on the long axis. It also contains a number of Bok globules, which are dense clouds of dust that are in the process of collapsing into a star.
The Trifid Nebula contains three types of nebulae in one: emission, reflection, and dark. Emission nebulae are clouds of gas that are energized by a star and re-emit light, usually a red hydrogen glow. Reflection nebulae are clouds of gas that reflect starlight. Dark nebulae are clouds of molecular dust that absorb starlight. I got to see both of these in big telescopes at the Atacama Lodge as well, and they were awesome! No red color (our night vision has poor color), but some blue and the dark nebulae too.
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