#195 - Sunday, July 7, 2019 - With My Own Eyes

After a late-ish first night of imaging under the dark Atacama Desert sky, I managed to sleep in until about 10:45 AM, but woke up with a raging headache.  Likely a combination of altitude, mild dehydration, and a late night.  Luckily we were well-stocked in the drug department, so I took some altitude sickness medicine and some ibuprofen.  And coffee.  The cure-all!

One of my two travel companions, John, cooked us a yummy breakfast of breakfast burritos.  We couldn't find any sour cream at the grocery store, or cheddar cheese, so we had the Chilean favorite gouda and some salsa we did manage to find.  He also did the dishes.  We told him he'd be allowed to sleep inside, with a blanket, and if he served us alcohol later in the day, maybe he could have a pillow too ;D

The water pressure had dropped during breakfast, so I waited to take a shower.  Finally in the early afternoon, it seemed to have gone back up, at least partially.  It took several minutes to warm up, but that was fine.  But then, halfway through my shower, the pressure dipped again, and it got cold!  So I wrapped up fast and hopped out.  Boo!

We decided not to go anywhere that day -- we were tired, particularly from the altitude, and after all of the adventures we'd had so far, a break was much needed.  So I worked on backing up photos and getting things organized.

At sunset, I went and found the Atacama Lodge owner Alain, who had dug up another counterweight for me, flipped the telescope around on its dovetail so that I'd have more room to push it forward for balance, and installed a Pegasus electronic focuser.  That one was a surprise, so I quickly got the driver installed for it.  Ultimately, however, I wasn't able to get my computer to talk to it, so I had Alain come back and disengage it so I could focus the ol'-fashioned way.  He told me to just use FWHM instead of a Bahtinov mask since it led me astray the night before.

I got it focused and went to align the mount, but then the power cable fell out.  Alain had split the cable coming out of the power supply to share with the focuser, and I think the plug he had on it was a little loose.  I tried the one on my ZWO camera to see if it was just the power supply or something else, but although the hand controller turned on, the mount itself didn't, and the hand controller said it didn't have any communication with the motors.  After being unsuccessful at finding another cable, and with Alain busy with tour groups, I gave up on the mount and turned my attention to my own Sky-Watcher Star Adventurer with my DSLR.

I put my 35mm f/1.8 lens onto my Nikon D5300 and pointed it toward the southern Milky Way, centering it on the Coal Sack Nebula.  It also captured Alpha Centauri, Beta Centauri, and the Southern Cross.

Coal Sack Nebula, with my Nikon D5300, 35mm lens @ f/1.8, ISO-1600, 60s

With the DSLR off and running, I went back inside to process my solar eclipse images until the scopes freed up after the tour groups left.  I wanted to make my composite corona image and get it out there before too much time elapsed after the eclipse!  The processing went really well, and you can see the result here on AstroBin.  I wrote in my eclipse day blog post about capturing the image, and then after the 2017 solar eclipse in the US, I wrote up a post about how I created the composite for that eclipse, and I used the same method for this one.

One of the tour groups

Later on, Alain took a look at the powerless mount, but couldn't immediately figure out what was wrong.  He helped re-polar-align my Star Adventurer, which went on to provide great images the rest of the night.  I pointed the camera up high in a gorgeous part of the Milky Way and let that run.

*drools*

Back in the lodge, John melted some of the chocolate over warmed crossaints, which made for a delicious and warm midnight snack on a chilly night.

We wandered up to the scope field after that, since all of the tour groups were gone, and split some time on the scopes with parts of the French group.  Now, I sometimes pepper in visual observations in between fussing over my cameras, mounts, and computers when I'm at the club's observatory or at a star party, but since the mount wasn't running and the 35mm lens on the Star Adventurer hooked up to AC power required little attention, I spent most of the rest of the night witnessing the wonders of the southern sky with my own eyes.  I love astrophotography -- pulling signal out of the noise, getting this incredible image of an amazing object that is hard to believe really exists -- but there is a special kind of wonder with visual observing.  There's the challenge of finding the object, then observing deeper into it to see what can be seen, and on top of that, there's the knowledge that some photons that were emitted thousands or millions or lightyears away are finally coming to a rest in your eyes.

First, the French had the the Tarantula Nebula up in the 28-inch Dob, an enormous nebula in the Large Magellanic Cloud (like actually in it, meaning that it's something like 1000 lightyears across!), which under low power looked "dim and chunky, with three chunks" according to my hastily-typed notes.

At our request, we looked at the massive globular cluster 47 Tucanae, which is just off the edge of the Small Magellanic Cloud (but belongs to our galaxy).  It has something like ten thousand stars packed into 120 lightyears, and is second only to Omega Centauri in brilliance.  It was dazzling in the 28-inch Dob under dark, steady skies!  It seemed to spiral around in my eye.

Next,we looked at NGC 253, the Silver Dollar or Sculptor Galaxy.  It's nearly edge-on to us, but not quite.  It looked positively 3D in the telescope!  Very cool effect standing out against the background darkness.

Over in the nearby 24-inch Dob, another one of the French group had pulled up the Helix Nebula.  The other nebula filter was off somewhere, so it just looked like a formless smudge, unfortunately.

Back over on the 28-inch, a higher-power eyepiece had been inserted, and the Tarantula Nebula re-acquired.  I took a look, and HOLY COW it was incredible!  It had so much structure in light!  And it was in another galaxy!!  It showed a green-blue color, forked with dark nebula clouds spreading out from the middle.  There was so much detail to take in, you could just stare at it forever.  What an incredible thing to see!

By this time, it was about 4 AM, and I looked east, hoping to spot the zodiacal light.  And there it was!  A dim, but definitely noticeable, column of light that extended at least up to zenith.  Alain showed us the latest image pulled down from his all-sky camera, which is extremely sensitive, and it showed the arc going all the way across the sky, from horizon to horizon!  It was really cool.  Zodiacal light is caused by sunlight that is scattered by interplanetary dust in the plane of the solar system (aka, the plane of the ecliptic).  It's called zodiacal light because the the band it lights follows the Zodiac signs, since these are constellations that are along the plane of the ecliptic.  The small particles of dust range in size from 10-300 microns (ten-thousandths of an inch)!  It is best observed in the western sky in spring after twilight, or the eastern sky in the fall before sunrise, when the ecliptic is highest.  In northern Chile, being in the southern hemisphere, the ecliptic was almost directly overhead, so it made for excellent conditions.

  Not the best photo of it, since I didn't have a fast-enough, wide-enough lens to do it justice, but you can kind of see the zodiacal light right behind the Pleiades!  Taken at 4:32 AM.

The French located a galaxy cluster in Fornax that I didn't quite understand what they were saying the name was, but it was a gorgeous, tight grouping of 5 galaxies I think, of which I spotted 4.  I also enjoyed some binocular views of the Pleiades, the Lagoon Nebula (M8), and the Andromeda Galaxy with my 10x42 Meade sport binos.  I could see Andromeda naked eye as well as a dim smudge, low on the horizon.  

Back at the scopes, we looked at M17, the Swan Nebula, which was absolutely gorgeous.  I always think it looks like a fountain spring.  It showed lots of structure and detail, especially with the OIII filter.  I suggested we also look at M20, the Trifid Nebula, with the 24-inch while I was over there.  I could see the emission part of the nebula (which is red in pictures, but I just saw the blue-green component), and the dark nebula that criss-crosses it, but I couldn't quite eke out the reflection nebula portion.  Maybe if I'd spent more time with it.  It was also getting lower in the sky by this time of the morning.

After shutting down my gear, I finally crawled into bed at 5:45 AM.  What a night!

[ Update July 25, 2019 ] 

Now that I'm finally writing this post, I'll include a blurb on the Coalsack Nebula image that I mentioned above, only now it's processed!  I knocked that one out last Wednesday after work.

Date: 7 July 2019

Location: Atacama Lodge, San Pedro de Atacama, Chile

Object: Coalsack Nebula

Attempt: 1

Camera: Nikon D5300

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

Accessories: N/A

Mount: Sky-Watcher Star Adventurer

Guide scope: N/A

Guide camera: N/A

Subframes: 33x60s (33m)

Gain/ISO: ISO-1600

Acquisition program: Intervalometer

Stacking program: PixInsight 1.8.6

Post-Processing program: PixInsight 1.8.6

Darks: 56 (46F)

Biases: 20 (46F)

Flats: 0

Temperature: mid-40s

The Coalsack Nebula is a massive dark nebula just above the Southern Cross constellation.  It's relatively nearby, only 600 lightyears away, and spans about 70 lightyears.  Dark nebulae are clouds of molecular dust that absorb light, and the Coalsack appears as a "hole" in the Milky Way (although really is stands between us and the galaxy's core).  In some Australian Aboriginal cultures, the Coalsack was the head of a massive emu in the sky.  In others, it's the head and shoulders of the "law-man," watching the people to keep the traditional laws.  In Inca astronomy in South America, it was known as Yutu, which is a partridge-like southern bird, also known as a tinamou.  It's also featured in several sci-fi references, including the original Star Trek series, 2001: A Space Odyssey, and many more.

In PixInsight, I did:

- Created master bias with ImageIntegration

- Generated superbias from master bias

- Calibrated dark frames with superbias (Linear Fit clipping)

- Calibrated lights with darks and superbias

- SubframeSelector

- 23.07 arcsec/px

- 0.115 e/ADU

- Best frame: DSC_0234 (85.502)

- Debayered

- Registered with StarAlignment

- Stacked with ImageIntegration

- Linear Fit clipping

- Cropped with DynamicCrop

- Applied DynamicBackgroundExtraction

- Denoised with MultiscaleLinearTransform

- Color corrected with PhotometricColorCalibration

- Stretched with HistogramTransformation

- Tweaked with CurvesTransformation

- Used star mask and ColorSaturation to reduce pink color of stars

- Tweaked again with CurvesTransformation

This one had some purple-y stars that were difficult to reduce, but I was able to correct them somewhat.  It's an artifact of the lens.  

[ Update August 18, 2019 ] 

Getting closer to the bottom of the data pile!  I need to start working on making videos out of my timelapse data too...

Anyway, here are the Magellanic Clouds!

Date: 7 July 2019

Location: Atacama Lodge, San Pedro de Atacama, Chile

Object: Magellanic Clouds

Attempt: 1

Camera: Nikon D5300

Telescope: Nikon 35mm f/1.8G

Accessories: N/A

Mount: Sky-Watcher Star Adventurer

Guide scope: N/A

Guide camera: N/A

Subframes: 44x30s (22m)

Gain/ISO: ISO-1600

Acquisition method: Intervalometer

Stacking program: PixInsight 1.8.6

Post-Processing program: PixInsight 1.8.6

Darks: 30

Biases: 0

Flats: 0

Temperature: 31-36F (mostly 33)

For this dataset, I had accidentally left the camera set to 30s, but it worked out all right anyway, since the shorter exposure time that less periodic error could creep in, which gave me a crisper image.  The red glow on the right side is from being low on the horizon (I rotated the camera to squeeze them both in).  

As I was starting to process this one, it struck me that I have imagery of the Magellanic Clouds!  I'm so happy that I got to go image in the Southern hemisphere.  I knew I wanted to do it at some point, but I didn't think I'd get to do it this soon!  Super super thankful.  

Here's the PixInsight process:

- Integrated darks with ImageIntegration to make master dark

- Calibrated lights with master dark

- SubframeSelector:

- Scale: 23.07 arcsec/px

- Gain: 0.115 e/ADU

- Debayered

- Registered with StarAlignment

- Stacked with ImageIntegration

- Combination: Average

- Normalization: Additive

- Pixel rejection: Linear fit clipping

- Cropped with DynamicCrop

- Applied DynamicBackgroundExtraction

- Denoised with MultiscaleLinearTransform, with lum mask

- Color-corrected with PhotometricColorCalibration

- Applied Deconvolution, with range_mask-star_mask, DynamicPSF, 10 iterations

- Stretched with MaskedStretch

- masked_stretch_2: undid stretch, did another DBE but division to help with gradient, then

did MaskedStretch

- MaskedStretch pulled out some weird star gradients

- Undid MaskedStretch and stretched with HistogramTransformation instead

- Tweaked with CurvesTransformation

- Went back to un-stretched image, applied DBE again with more sample points in red area

of upper right hand corner to target the gradient

- Stretched with HistogramTransformation, adjusted with CurvesTransformation

There is usually some trial-and-error involved!

[ Update: October 13, 2019 ] 

I've gotten sidetracked on processing data from my backyard, and I forgot I had one more dataset from Chile: another Milky Way shot!  The one I showed the image of on my DSLR screen above.

I struggled with the pink-purple tone added to the stars from chromatic aberration of the lens, but got it down to acceptable levels I think.  Love the dusty detail here!

Date: 7 July 2019

Location: Atacama Lodge, San Pedro de Atacama, Chile

Object: Milky Way

Attempt: 10

Camera: Nikon D5300

Telescope: Nikon 35mm f/1.8G at f/2.2

Accessories: N/A

Mount: Sky-Watcher Star Adventurer

Guide scope: N/A

Guide camera: N/A

Subframes: 38x120s (1h16m)

Gain/ISO: ISO-1600

Acquisition method: Intervalometer

Stacking program: PixInsight 1.8.7

Post-Processing program: PixInsight 1.8.7

Darks: 23 (38F)

Biases: 0

Flats: 0

Temperature: 34-39F

This view is through my 35mm f/1.8 lens, and peers deep into the southern part of the Milky Way, but still up high near the core. Just off the right edge is a part of the Milky Way familiar to northern observers -- a little bit of the Pipe Bowl Nebula, the Butterfly Cluster (M6), and Ptolemy's Cluster (M7) above. To the left of that area you can see some of the pink fuzziness of the Cat's Paw Nebula. Near the center lie the beautiful open clusters of Collinder 316, Trumpler 24, and NGC 6231, with open cluster NGC 6124 nestled in the dust clouds below. The left portion of the image is within the southerly constellation Norma. The bright dot in the far lower right corner is interloper Jupiter.  You can check out the labeled image in AstroBin.

Sometimes my wide-field Milky Way images can come out with over-dominant stars, but this one did okay.  I did reduce the stars a bit using this tutorial from Light Vortex Astronomy that works reasonably well most of the time.

Here's the whole process:

- Stacked darks with ImageIntegration

- Calibrated lights with master dark using ImageCalibration

- SubframeSelector:

- Scale: 23.07 arcsec/px

- Gain: 0.115 e/ADU

- Highest-scoring subframe: DSC_0265 (85.351)

- Debayered

- Registered with StarAlignment

- Stacked with ImageIntegration

- Combination: Average

- Normalization: Additive

- Pixel rejection: Linear fit clipping

- Cropped with DynamicCrop

- Background removal with AutomaticBackgroundExtraction

- Denoised with MultiscaleLinearTransform, with luminance mask

- Corrected color with PhotometricColorCalibration

- Stretched with MaskedStretch

- Adjusted with CurvesTransformation

- Reduced pink tone in stars by making a star mask with StarMask, then desaturating with ColorSaturation

- Reduced star sizes use Light Vortex method

- Increased saturation with CurvesTransformation

- Used dilated star mask to reduce pink tone again, expanded ColorSaturation de-saturation into purple

- CurvesTranformation with the star mask helped some more

- Tweaked a bit more in Camera Raw in Photoshop

What a great trip!  I got so many amazing images!  Now to decorate my house with them.  😁  (You can too!)

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

Previous post: #194 - Saturday, July 6, 2019 - In the Atacama Desert

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#194 - Saturday, July 6, 2019 - In the Atacama Desert

After a few more days in La Serena following the solar eclipse, we started a three-day road trip up the coast and then inland to Calama, and then on to San Pedro de Atacama.  We stayed overnight in Chañaral and Antofagasta on the way up.  The desert landscape was like from another world!  There were many places where there was absolutely nothing but rock and sand.  And the occasional guanaco.  We got out at a guanaco observing spot near the Paranal Observatory, and sure enough, we saw one!  And then it made a funny noise and ran off.  Besides the crunching of our feet on the gravel, it was absolutely, perfectly silent.  We couldn't even hear the wind in this little valley we were in.  I had never heard such wide-open silence before; it was totally eerie and incredible.  A Girl Scout badge I led with a middle school group when I was in college talked about different kinds of pollution, including sound pollution, and it talked about the quietest square inch of space on Earth.  When a car wasn't passing by, this had to be it!

We were basically on Mars.  But with more oxygen.

What made it especially crazy was the fact that we were not at all far from the ocean.  In some places, we could see barren desert one one side of the road and crashing waves on the other!

The highway we were on took us past the Paranal site of the European Southern Observatory, and while we hadn't been able to get a tour there when we tried, we hoped there might be a cancellation, and at least we could see them from a distance if not.  We were out of luck, but the gate guard let us use the restroom there and re-fill out waterbottles, which was very nice.  We took plenty of pictures from the parking lot.  Yay for my long lens!

Paranal Observatory, from a distance

Posing with the sign

The altitude at the parking lot was around 7800 feet!  

In Antofagasta, our hotel was right on the beach, so we enjoyed watching the waves ceaselessly roll in, ever-changing, but ever the same.  It was hypnotizing.  

The Pacific Ocean -- the color of the water was beautiful!

On the third day of the road trip, Thursday, we drove for three hours from the coast up to the 7400 feet of the town of Calama.  We stopped at a large grocery store there called Jumbo (like Chilean Walmart, but a little nicer), since it was easier to get supplies there than in San Pedro de Atacama.  However, due to the sudden change in altitude, we were all lethargic, sick, and crabby.  So we tried our best to hold ourselves together while we shopped quickly, and then drove the next hour to San Pedro de Atacama, and the Atacama Lodge.

The Atacama Lodge is an amateur astronomer's dream land, owned by French ex-pat Alain Maury, himself an astronomer who grew tired of the light pollution and the politics of France and sought better skies.  It grew to be part robotic scope operation, part astro-tourism, a few kilometers south of the touristy village of San Pedro de Atacama in northern Chile, lying in the shadow of the volcanic Andes Mountains.  He hand-built a sunflower field of telescopes, with which he hosts nightly tours in three languages to showcase the wonders of the Southern skies.  

Less of a hotel and more of a nice set of adobe cabins, the accommodations were charming and fun.

My room

John & Beth's room

Gorgeous mosaic tile in the bathroom

Kitchen & dining area, complete with cookware and dishes.  And, very importantly -- a coffee maker!

Actual thatch roof!

Bonus, it had a heater, which none of our previous hotels had, which was a godsend.  The forecast showed that it would dip into the 30s every night!

Once Alain himself finally returned from a grocery run to Calama, he quickly got me set up on the Sky-Watcher AZEQ6 with a Takahashi FSQ-85ED before he had to zip off for that night's astro-tours.  The mount was located in a giant motor-driven rolloff shed that contained several robotic scopes owned by people from around the world, including one owned by none other than Guylain Rochon, the man behind the BackyardNikon and BackyardEOS camera-control software that I use.  Since the shed automatically opened and closed at sundown and sunup, I'd be able to leave everything connected, and it would be kept safe from the heat and the dust during the day.

Alain ran back to his house and got the key for the little half-door, but couldn't get it to unlock.  After much effort, including attempting to remove the lock from the door (he just jumped over the half-wall to get to the inside), we finally just set up a chair on the inside and outside to use to help climb over the wall!  I got pretty good at it by the end of the night in the dark.

The Takahashi didn't have a guide scope attached, but Alain said it wouldn't need it, and I hoped he was right.  I had prepped the software on my computer for plugging the hand controller in via serial-to-USB cable and running it using the SynScan driver and app, but he didn't have that cable -- instead, the AZEQ6 had a direct USB cable, like the Celestron CGX-L mount, which I had no idea it had.  This required EQMOD to run.  Before it got properly dark, I went back to the wifi in the lodge to install EQMOD, but I couldn't get the driver to show up in ASCOM when I tried to connect to it in Cartes du Ciel.  So instead, since I wasn't guiding, I just used the hand controller and didn't bother with trying to control it from my computer.  I just hoped the gotos would be good enough to not need a finderscope, which it also didn't have.  I got my ZWO ASI1600MM Pro and Starlight Xpress 2-inch filter wheel attached without issue.  Alain had a Takahashi-to-T-thread adapter handy (although I had brought mine just in case). 

My ZWO ASI1600MM Pro camera and Starlight Xpress filter wheel attached to Alain Maury's Takahashi FSQ-85ED on a Sky-Watcher AZEQ6 mount.

Sunset was gorgeous, especially the way the Andes changed colors.  I have a timelapse video that I'll put together (eventually), which I'm really excited about.

Once it got darker, I needed to get the camera focused.  I had it slew to a bright star, but since I wasn't sure how well polar aligned it was at the moment, that star did not end up in the field of view of the camera.  I cranked up the screen stretch on the histogram in SharpCap, but still couldn't even see any giant blobs.  So instead, I slewed it myself over toward some patch of the Milky Way, where I knew there would be stars in the field no matter where I pointed.  After over-stretching the histogram, I saw some giant blobs, and was able to get the scope roughly focused for alignment.  I would like to take a moment to point out something amazing -- this is a one-second exposure.  There were so many stars!  It was so dark that many more stars than usual could stand out.

Wowee!!

Next, I ran the polar alignment process in SharpCap, which it was capable of doing in the southern hemisphere the same way it does in the northern -- by way of plate solving.  

It was during this process than I ran into my next stumbling block -- Alain had showed me where the RA and dec clutch knobs were, but I couldn't remember where the RA one was.  So I tried various things for about 15 minutes before I finally figured it out!  But I finally got the darn thing polar aligned.  I also balanced it before polar aligning, although I wasn't able to balance it in dec because I ran out of dovetail to move it any more forward to compensate for my camera gear on the back.

Next was alignment, which I did with the hand controller in a very similar process to Celestron.  The stars landed in the FOV for every star, which was very exciting and helpful.  Finally, after focusing on a bright star with the Bahtinov mask I'd brought with me, it was time to line up my first target.  I chose something easy -- compact and relatively bright -- for my first target: Centaurus A.  It's a large, oddly-shaped galaxy, somewhere between 10-16 million lightyears away, also sometimes called the Hamburger Galaxy. Viewing it visually makes that moniker choice obvious -- it was a bright upper and lower hemisphere, split by a thick dark band of dust, making it look very much like an enormous hamburger in the sky.  You can see it from the southern United States -- from the 29 degrees north latitude of the Texas Star Party, it crests at 12 degrees off the horizon or so, just high enough to let it peak for an hour or two above the hills.  But here at 22 degrees south, it was quite high in the sky, with much less atmosphere between me and it.  Thanks to the dark skies, it was very easy to see with 1-second exposures in SharpCap, so I centered it by hand, switched over to SequenceGenerator Pro, keyed up the sequence I wanted, and let it run.  The plan I had developed several months ago for which targets I was going to image when called for starting with RGB that night before changing targets for the second half of the night -- with RGB, I'd have a complete dataset, in case something broke later in the week and I didn't get to finish.  Having a luminance channel is great, but not required.  

I took a few test frames first to see how long it would track for, and I got as far as 5 minutes with just the tracking, and my stars were still mostly round!  I set the exposure time to 3 minutes so I could get more frames, and because that was long enough for the ZWO in these dark skies with this brighter target.  

Single 180s red channel frame, screen-stretched & zoomed in

The RGB frames looked a little out of focus, so partway through the night, I slewed over to a nearby bright star and checked the focus with a Bahtinov mask.  I tweaked it slightly, but it was very close.  I cinched down the focus lock a little tighter, slewed back to Centaurus A, and carried on.

Single 180s blue channel frame

While the ZWO was running, I set up my Sky-Watcher Star Adventurer with my Nikon D5300 and 70-300mm lens attached again, which I found some space for in the shed as well. Polar aligning this one was going to be harder -- I had no SharpCap to help me.  (I am working on putting together a rig for one of my guidescopes that will attach to the second camera screw on the Star Adventurer, which I could use both for polar alignment and for auto-guiding.  Yes, the Star Adventurer has a ST-4 port!)  I used my cell phone to get it pointed due south and get the elevation close to correct, but I couldn't see the Octans trapezoid in the polar scope still.  So I pointed it to the eastern horizon and then to zenith to do some drift alignment, which helped a bit.  I pulled the zoom on the lens back to something around 135mm, focused it, and then turned it to the glorious Eta Carinae Nebula.  I was able to get about 90s exposure times with minimal streaking, so I set it there and let it run.

Later in the night, I had a brainwave -- the Takahashi clamshell ring had a 1/4-20 tripod screw on the top!  So I took one of my ball heads and attached it to the top, and grabbed my Nikon D3100 and my new 35mm f/1.8 Nikon lens and got everything attached.  I aimed it up somewhere in the middle of the Milky Way (yes, up, overhead!!), vaguely toward M8 & M20, and took a 30-second test exposure at f/2.  I went to check on my D5300, and caught a quick glimpse of the D3100 image once it had completed and flashed onto the screen, and I froze.  I stood there for a moment, dumbfounded.  Did I just see what I think I saw?  I fumbled for the Review button, and it re-appeared on the screen. Holy McShitNuggets (were the actual words that came out of my mouth), it was incredible!

30s exposure pointing up toward the Milky Way with my Nikon D3100 and 35mm f/1.8 lens at f/2.

So I just left the camera pointed there, set it to 60s exposures at ISO-800 and f/2, and let it roll!

After all this work, everything was clicking away happily, so I went back to the lodge to warm up, take a break, and have a snack.  After the break, John, Beth and I wandered over to a lone 24-inch Dob beside another one of the cabins, which was being used by part of a large French group that was also visiting the Atacama Lodge.  Between people, we snuck in to observe the massive globular cluster 47 Tucanae.  Located about 13,000 lightyears away, it has about 10,000 stars packed into a ball about 120 lightyears wide.  It's large and bright enough to be easily seen naked eye just off the edge of the Small Magellanic Cloud, and is second only to the Omega Centauri cluster.  47 Tuc may even have a black hole at its center.  It spans an area of the sky that is wider than the full Moon by almost twice!  It was so spectacular in the large telescope that it prompted me to shout "Holy mackerel!" (yes that is what I actually said), which garnered some chuckles from the French.  

We walked up to the main field to nab a scope up there to use for the night, but the French had commandeered all of them.  So I went back over to my cameras to check on things.  Eta Carinae had gotten too low to continue imaging, and it was time to change targets on the Takahashi as well, so I took the opportunity to swap lenses between the Nikon D3100 and D5300 so I could put the longer lens on the mount that was tracking more precisely.  However, this proved to be too heavy for the Sky-Watcher AZEQ6 mount, for which I already had the counterweight at the bottom of the rail, and gravity overcame the RA clutch knob and the scope slipped over!  I caught it, and it was not like it was totally loose or anything, but it did mean that I had to start over with alignment.  I tried to tighten down the RA axis some more, but I couldn't get it any tighter.  Alain had said he'd look for a second counterweight in the daylight.  So I took the camera off, re-aligned (gotos weren't as good this time, however), and pointed it to my second target for the night, a galaxy in the southern constellation Pavo called NGC 6744.  

I started with the L channel this time, but it looked out of focus.  So I checked focus again with a Bahtinov mask, but it was still perfect.  I thought that maybe it was evenly-sided periodic error or something.

180s luminance image of NGC 6744, zoomed in

I pressed on anyway, since I wasn't sure what else to do.  Then I went over to my Nikon D5300 and set it up on the Small Magellanic Cloud with the 35mm lens.

Around 3:30 AM, I was petering out.  The long day and high altitude were making me extra-tired.  So I shut down the power to everything like Alain had asked me to, and got into bed around 4:15 AM.

It was a great night!  I got my imaging rigs rolling, the sky was incredible, and the Milky Way was simply mind-blowing.  We couldn't quite see any color, but the transparency might not have been the clearest that night due to the earlier clouds.  There were also some clouds still down near the horizon.  But the Large and Small Magellanic Clouds that appeared later in the night were easy to spot, as well as a large number of deep sky objects with averted vision.  I couldn't wait for the rest of the week!  We had five full nights under these skies!

[ Update July 21, 2019 ] 

I processed this image last weekend, but now that I finally got this log entry written, here is the Eta Carinae Nebula!

Date: 6 July 2019

Location: Atacama Lodge, San Pedro de Atacama, Chile

Object: Eta Carinae Nebula

Attempt: 1

Camera: Nikon D5300

Telescope: Nikon 70-300mm lens @ 90mm, f/4.5

Accessories: N/A

Mount: Sky-Watcher Star Adventurer

Subframes: 54x90s (1h21m)

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: 33-36F

See on AstroBin

The stars came out a little bloated, and it turns out I was closer to 90mm than the 135mm-ish I thought I set it to, but isn't it a gorgeous region??  

Featured here is the Eta Carinae Nebula, which is a massive stellar nursery located in the constellation Carina, or "keel of the ship."  It's about 8,500 lightyears from us, and is 460 lightyears across!  From our perspective here on Earth, it's four times larger and is brighter than the famous Orion Nebula!  Unfortunately, however, you can only see it from southern skies.

It has a multitude of interesting stellar objects contained within.  One such object is the star Eta Carinae itself, which is an extremely luminous hypergiant star, weighing in at 100-150 times the mass of our Sun, and outputting four million times more light.  Due to its large mass, it is likely to go supernova in the near future ("near" in astronomical terms, of course). 

Immediately surrounding the star Eta Carinae is the Homunculus Nebula (probably the coolest nebula name ever, meaning "Little Man" in Latin, which sounds much less cool), which is the result of a huge outburst from Eta Carinae seen on Earth in 1841, which for a short time made it one of the brightest stars in the sky.  It's a very oddly-shaped nebula, and there are some very cool pictures out there of it!  

Also pictured here are the Southern Pleiades to the left, and the tighter open cluster NGC 3532 (also called the Pincushion Cluster, Football Cluster, or Wishing Well Cluster) to the upper right, as well as several other clusters.  

Here's how I processed it in PixInsight:

- Since I don't have any 90s dark frames at those temperatures, I skipped right to SubframeSelector

- Image scale: 8.97 arcsec/px

- Gain: 0.115 e/ADU

- Highest scoring frame: DSC_0050 (88.648)

- Debayered

- Registered with StarAlignment, with DSC_0050 as reference

- Stacked with ImageIntegration, using Linear Fit Clipping for rejection

- Cropped with DynamicCrop

- Applied DynamicBackgroundExtraction

- Color corrected with PhotometricColorCalibration

- Tried Deconvolution, but didn't like how it made the stars look

- Denoised with MultiscaleLinearTransform

- Stretched with HistogramTransformation

- Applied HDRMultiscaleTransform, 7 iterations, with lum mask

- Touched up with CurvesTransformation and HistogramTransformation

I'll probably go back and re-process this one and try to get the stars to not dominate the image as much.  We just discussed this on The Astro Imaging Channel last week, so I'll have to go back and re-watch it.

[ More update July 21, 2019 ] 

After I posted some of the screenshots of the Centaurus A galaxy, I realized the data didn't look as bad as I thought.  So I spent the later part of the afternoon processing that data.

I realized when I was filling in my documentation text file that somehow the gain got set to only 10 for this dataset, for which I have no dark frames.  I tried processing with gain 0 frames, but the calibrated light frames came out pretty much nuked of light.  So I went ahead and processed without calibration frames, but they turned out not to be that necessary, since I had my sensor cooled to -30C.  I didn't take any luminance data, although in a future re-do of this dataset, I might crop and re-scale this color data and add it to the luminance data I took of Centaurus A at the Texas Star Party.  It may or may not help, since Centaurus A was much lower in the sky -- and thus in the thicker, nastier part of the atmosphere -- but it might be worth a shot.

Anyway, here it is!

Date: 6 July 2019

Location: Atacama Lodge, San Pedro de Atacama, Chile

Object: Centaurus A

Attempt: 2

Camera: ZWO ASI1600MM Pro

Telescope: Takahashi FSQ-85ED

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

Mount: Sky-Watcher AZEQ6 (Alain Murray's)

Guide scope: N/A

Guide camera: N/A

Subframes: R: 28x180s

   G: 26x180s

   B: 10x180s

   Total: 64x180s (3h12m)

Gain/ISO: 10 (not sure how that happened)

Acquisition method: SequenceGenerator Pro

Stacking program: PixInsight 1.8.6

Post-Processing program: PixInsight 1.8.6

Darks: 0

Biases: 0

Flats: 0

Temperature: -30C (chip)

This might be only my 'official' second attempt, but I had tried to image it before but ran into other issues that led me to not keep that data.  So I'm happy to finally have an image of this cool galaxy!  It's not only cool to look at in its weirdness, but its weirdness has made it an interesting target of study.  Centaurus A is somewhere between 10-16 million lightyears away -- no one is quite sure.  It doesn't fit cleanly into any established galaxy category, and its odd shape is probably a result of a galaxy merger.  At the center of that galaxy is a 56-million-solar-mass black hole that is blasting out jets that move at half the speed of light and emit brightly in x-ray and radio.  They extend out to a million lightyears!  Very cool galaxy to look at.  It's also on the top-5 list of the brightest galaxies in the sky as seen from Earth, so it makes a good visual observing target.

[ Update August 8, 2019 ] 

Still plowing through Chile datasets -- here's the Magellanic Cloud!  It turned out to be just a hair out of focus, so the quality isn't that great, but here it is anyway.

Date: 6 July 2019

Location: Atacama Lodge, San Pedro de Atacama, Chile

Object: Small Magellanic Cloud

Attempt: 1

Camera: Nikon D5300

Telescope: Nikon 35mm f/1.8G @ f/2

Accessories: N/A

Mount: Sky-Watcher Star Adventurer

Guide scope: N/A

Guide camera: N/A

Subframes: 28x90s (42m)

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: 32-35F

I did try to apply some deconvolution to see what sharpening could be done on the SMC, and with a small number of iterations, it helped a tiny bit.  I did try MaskedStretch for stretching the image, but it blew out the small pink and blue halos around the stars, which I didn't like.  So I re-stretched it myself with HistogramTransformation instead.

Here's the whole process:

- No darks, calibrated lights with pre-made superbias using ImageCalibration

- SubframeSelector:

- Scale: 23.07 arcsec/px

- Gain: 0.115 e/ADU

- Highest-scoring frame: DSC_0162 (85.313)

- Debayered

- Registered with StarAlignment

- Stacked with ImageIntegration

- Combination: Average

- Normalization: Additive

- Pixel rejection: Linear Fit Clipping

- Cropped with DynamicCrop

- Applied DynamicBackgroundExtraction

- Denoised with MultiscaleLinearTransform

- Color corrected with PhotometricColorCalibration

- Applied Deconvolution using DynamicPSF, range_mask-star_mask, 10 iterations

- Tried MaskedStretch, but stars got pink and blue halos, so I stretched it myself

with HistogramTransformation

- Tweaked with CurvesTransformation

- Applied HDRMultiscaleTransform, 9 iterations

[ Update August 15, 2019 ] 

Still chugging through Chile data!  Being in the middle of a move makes finding time and energy to do this difficult!  But I finally had some chill time to work on it.  

I processed the stack of the Milky Way I took with the 35mm lens piggybacked on the Sky-Watcher AZEQ6 mount -- the "Holy McShitNuggets" dataset -- and the result was truly excellent!  There was also almost zero drift across the whole time of the stack, which was awesome and gave me nice round stars.

Date: 6 July 2019

Location: Atacama Lodge, San Pedro de Atacama, Chile

Object: Milky Way

Attempt: 9

Camera: Nikon D3100

Telescope: Nikon 35mm f/1.8G @ f/2

Accessories: N/A

Mount: Piggyback on Takahashi FSQ85ED, on Sky-Watcher AZEQ6

Guide scope: N/A

Guide camera: N/A

Subframes: 39x60s (39m total)

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: 31-35F

See on AstroBin

I just can't get enough of that Milky Way!!  There are several interesting things here.

- The super bright thing on the right is Jupiter
- In the lower right is the Rho Ophiuchi complex, which I've recently shared closer-up images of. The brighter yellow-orange star is Antares.
- The dark upside-down-U-shaped nebula to the left of Jupiter is the Pipe Bowl Nebula, a giant molecular cloud
- The two fuzzy red regions in the center of the image are two emission nebulae - NGC 6357 on top, and the Cat's Paw Nebula on bottom
- Up above NGC 6357 is open cluster M7, Ptolemy's Cluster
- In the lower left of the image, the other red nebula region is emission nebula IC 4628, surrounded by stars that are part of the Trumpler 24 open cluster

...and much more, of course!

This one was a pretty quick job.  Being one-shot color and not having issues or light pollution helped!

Here's the PixInsight processing:

- No darks or biases b/c I don't have a library for my D3100

- SubframeSelector:

- Scale: 25.9 arcsec/px

- Gain: 0.115 e/ADU (not actually measured, just borrowed from D5300)

- Debayered

- Registered with StarAlignment, using highest-scoring frame was reference

- Stacked with ImageIntegration

- Combination: Average

- Normalization: Additive

- Pixel rejection: Linear fit clipping

- Tried skipping DynamicBackgroundExtraction and did PhotometricColorCalibration instead, since there's pretty much no light pollution and most of the image is Milky Way anyway

- Denoised with MultiscaleLinearTransform, with luminance mask

- Stretched with MaskedStretch

- Tried with target background 0.15, interesting result, but not a huge fan

- Tried again with target background 0.10

- Tried again with 0.05, but too low, so did 0.08 - let me try some curves on that

- Adjusted with CurvesTransformation

- Applied the DarkStructureEnhance script

I wanted to have nice contrast between the bright and dark areas, and show just the insane number of stars in the bulge.  I also wanted the dark nebulae to stand out nicely.  But I didn't want it to look too hard or electronic either -- kind of softer, like how it might appear to our eyes if they were more sensitive.  As with many of my images, I'll probably mess around with it more in the future.  But I am quite pleased with this one!

Next post: #195 - Friday, July 7, 2019 - With My Own Eyes

Previous post: #193 - Tuesday, July 2, 2019 - Solar Eclipse in Chile

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#193 - Tuesday, July 2, 2019 - Solar Eclipse in Chile

The day finally arrived -- the solar eclipse over South America!  After a year of planning, the day was finally upon us.  I had packed my backpack and backpack camera case for my Sky-Watcher mount the night before, and I woke up at 5 AM to catch our 6:30 AM bus from a nearby hotel.  We decided to book our eclipse day with Ecoturismo, with whom we had a daytime boat tour of the islands off the coast of Chile a few days prior for spotting the Humboldt penguin, among other creatures.

We made a few stops along the way to the village of La Higuera, about 50 km north of La Serena, including a gas station that was packed with people also travelling for the eclipse.  But I successfully got my coffee, and everyone hit the bathroom and got some snacks, and we were on our way.

A large area had been set up just outside of the small village of La Higuera.  Many people just pulled their cars off the dirt road and set up chairs and BBQs.

Ecoturismo had a couple of tents set up with a bunch of chairs and a large BBQ for feeding us all day.

A mobile cell tower had been erected as well, although bandwidth was limited because there were so many people there.  Away from the area where most of us were was a series of white tents where several celebrities were said to be watching the eclipse.  

I took my time getting my gear set up after we selected a spot so I could make sure I had everything right.  It was only about 9:30 AM or something around there, and the partial eclipse didn't start until 3:22 PM.  I attached my Nikon D5300 equipped with my Nikon 70-300mm lens at 300mm to my Sky-Watcher Star Adventurer DSLR tracker mount.  To polar align it (roughly) in the daytime, I used my phone's compass and the tilt angle indicator of my phone using an app called GPS Status that I use all the time for astronomy.  I weighted down my tripod with an open sack thing I found on Amazon that velcros to tripod legs, and I filled it with some rocks that were lying around.  Then I plugged the mount into a cell phone battery and plugged my camera's USB into my tablet.  I had logged into BackyardNikon the night before and left it open, and I tested the capture speed (sometimes it will trigger pictures every 3.5 seconds instead of 2.5 seconds, depending on whether it thinks it's a USB connection or serial cable).  I put my Baader solar filter on the end of the camera lens -- it's a homemade one that was given to me with the Borg 76ED that I got from a fellow astronomy club member, and it was a little too big for my camera lens, so I lined it with bubble wrap before I left for Chile.  I aimed the camera at the sun and focused it, and then taped down the focuser.  Then I was all ready to go.

Then it was a long wait!  I walked around and took pictures, browsed Facebook, sat back and enjoyed the sunshine, and chatted with numerous passers-by who were curious and amazed with my rig.  Most of the other people in attendance didn't bring any cameras; they were just there to observe.  

Showing our tour guide Felipe the partially-eclipse sun through out solar binoculars.  It took some effort to convince people these were safe because of their special built-in filters, which means that they were well-educated on the risks!

Beside where my group was hanging out was a Chilean family, and a pre-teen boy was trying to figure out a way to capture the partial phases with his Canon DSLR after seeing the sun through our sun-oculars.  He cut up a pair of solar glasses and taped it to the aperture, but it wasn't big enough to cover the whole thing.  I helped him out (with my terrible Spanish), and we found some other cardboard pieces and tape to block the rest of the aperture. Then I helped him with the settings, and showed him how to chase the sun as it moved across the sky.  He was very grateful and excited!  I told him he could remove the filter during totality.

I checked my rig periodically and adjusted the camera as needed to keep the sun centered (my polar alignment wasn't perfect, obviously).  I did accidentally kick the tripod at one point, but it wasn't too hard to get it back where it needed to be.  Finally, we had first contact, and it was only a minute or so after that that we could see the moon just edging over the sun through our sun-oculars.  It was a few more minutes before you could see it without magnification through the solar glasses.

I went over to my tablet about a minute or so before the partial phase started and hit "go" on my partial phase script.  This took a few different settings of images every 5 minutes on repeat.  

As the moon covered more and more of the sun, the quality of the light started to degrade, and I started looking for the pinhole effect, where light shining through a hole would have the crescent shape instead of a fully-lit circle.  I was looking around for something with small-ish holes, since that's easier to see than criss-crossing your fingers, and I found it -- the chair on my traveling companion Chris' cane had holes in it that were perfect!  So I tilted the chair toward the sun, and sure enough, you could see half-moon-shaped shadows of the holes on the ground.  I looked up a couple words in Spanish to explain this to the people around me, and then went and showed a bunch of people the effect.  My friends called me the science ambassador!

At long last, totality drew near, and I went over to my laptop to prepare the script for totality, which I would start at one minute till.  I called out times in English and Spanish for the people around me, started the script, and took off the solar filter at 20 seconds.  I didn't need to call out the last 10 seconds because I great shout went up, and nobody could hear me anyway.  I watched the moon blot out the entire sun, and it was an utterly eerie and incredible sight.  The sky darkened suddenly, and the corona slowly brightened into view.  People were shouting and cheering, and I took a video on my other DSLR at the beginning of totality to capture the moment.  

My traveling companion Manning shoved a pair of binoculars into my hands saying he could see prominences, but I didn't see them.  I did admire the corona in the binoculars, something I missed during the 2017 solar eclipse in Wyoming.  Then I took some wide images of the eclipse with my other DSLR, and I looked around to see the 360 degree sunset.  It was mostly cut off for us by the mountains, but I could see it all along the west, where they were lower.  I also looked around for stars and planets, and saw quite a few!  Venus was shining very brightly below the sun, and I looked for Jupiter in the east, but I think it was too low behind the mountains.  I thought I saw Mars and Mercury, but I wasn't 100% sure it was them.  I saw several stars, including Sirius, possibly Rigel, Procyon, Canopus, Alpha Centauri, and Arcturus I think.  

Nikon D3100, 18mm, f/3.5, 1/50s, ISO-400

Because the sun was lower in the sky, it looked larger (much more so than the above image indicates), but the corona didn't appear to be as large as the one in 2017.  There were also no sunspots earlier, and there has been very little solar activity lately.  

Seeing the sun as a black hole surrounded by a shimmering halo is totally eerie.  Your brain doesn't quite know what to make of it.  It was beautiful, natural and alien at the same time.

Then, just like that, my phone solar eclipse app ("Solar Eclipse Timer" on Android at least) was announcing "glasses on!", and I watched the sun re-emerge, which was spectacular.  Then I put the filter back on my camera, and kind of stood there for a bit, unsure of what exactly to do.  It went by so fast, it felt like less than 10 seconds!  Finally I went to check on my images, and the last couple with the thin sliver through the solar filter looked a little out of focus.  My heart sank.  Were they all out of focus??  I scrolled through and checked -- they were, by just a hair.  I had taped down the focuser, but the zoom had slid back at some point, which put it a little out of focus.  However, I held out hope that they would still look good on a larger screen, as long as you didn't zoom in.  I got some cool shots!

Just before second contact

Nikon D5300, 300mm, f/5.6, ISO-200, 1/2500s

Inner corona

Nikon D5300, 300mm, f/5.6, ISO-200, 1/400s

Outer corona

Nikon D5300, 300mm, f/5.6, ISO-200, 1/8s

Diamond ring at third contact

Nikon D5300, 300mm, f/5.6, ISO-200, 1/800s

I didn't have the diffraction spikes in the 2017 images because I used a circular telescope aperture instead of the straight lines of the iris inside of a camera lens, but I think it's a cool effect.

I re-started the partial eclipse phase script, and we hung around as the moon moved away from the sun's disk.  We didn't get to see the sun completely re-emerge, however, since they sank behind the hills together, heading toward sunset.

Nikon D5300, 300mm, f/5.6, ISO-200, 1/2500s

Sunset was also a gorgeous moment to witness.

Finally, it was time to pack up and head back to La Serena.  Well, us, and 250,000 other people as it turned out!  It wound up taking us 4.5 hours to go the 50 km, and that was with our intrepid tour guide taking some American-style "shortcuts" around the other cars!  We finally got back to the hotel at 10 PM, and I stayed up for a little while longer to post a few images (after installing Lightroom so I could apply the watermarks).

It was a very long but incredible day!  It was an awesome experience sharing this solar eclipse with a few of my friends, strangers interested in astronomy, and many others who just wanted to witness this incredible spectacle.  

Does viewing two total solar eclipses in a row make me an eclipse chaser? :D

[ Update: July 7, 2019 ]

While I was waiting for the moon to set to go out and do some observing from the Atacama Lodge the second half of my trip to Chile, I processed some of my corona images together into a single composite image.  Cameras don't have as high of dynamic range as our eyes -- our eyes can see many levels of brightness at the same time, but the camera sees far fewer.  As you can see in my images above, shorter exposure times make the dimmer outer corona dark, while longer exposure times make the brighter inner corona too bright to see any detail.  There are many ways to process images to reveal multiple levels of brightness, such as people who make neat moon composites, the Milky Way behind brightly-lit foreground scenes (although this can sometimes also be done in a single shot with clever lighting), etc.  The method I used here is the same as the one I used for the 2017 eclipse, known as the Pellett method, described here by astrophotographer Jerry Lodriguss, and in more detail in the blog post made it about here.  

I won't put all the details here, since they are all in my blog post tutorial.  But here's the rundown.

First, I selected several images with different exposure times, ranging from 1/4000s to 1s, which turned out to be 10 for me.  Then, I radially blurred each one, and saved out those files as TIFFs.

Original (1/8s)

Blurred

Next, I subtracted the two images from each other with an offset of 128 to get a low-contrast difference image between the two that pretty much just contains the streamers themselves.

Difference image

Then, I added all of the difference images together.

Difference images added together

Here, you can see the streamers, some prominences, and the edges of the sun, since the input images weren't all taken at the same time, so the moon had translated across the sun's surface a bit.  Next, I multiplied this image by the longest-exposure input frame.

Since the edges of the moon are messy and it didn't really stick around during the subtractions anyway, I copied the moon from one of the longer input images and enlarged it a bit to cover up the movement.  Finally, I toyed with the exposure, contrast, saturation, and denoising settings, and covered up a few dust spots using clone stamp, and have this final product!

So awesome!  You can see lots of detail in the corona, and even one of the little prominences.  It's a little hazy because it was quite low in the sky, only 13 degrees above the horizon, which made it a bit hazy.  One thing that is really interesting about the corona this time is how symmetric it is.  This is likely due to the solar minimum we've been in for a while, which also means we haven't seen much in the way of sunspots for about the past year.  So here's hoping that the 2024 eclipse across the US has even more excitement!  

One last note I'll make here for anyone who's wondering - my images are rotated about 45 degrees from the sun's true orientation as observed visually from the same spot.

Science

Another really great thing about this eclipse in particular is that it crossed over so several professional observatories that exist in that area of Chile, including Cerro Tololo and La Silla, and a lot of research observations were taken at those locations.  Much is still unknown about the sun's corona, which is essentially the sun's outer atmosphere that extends billions of miles into space, encompassing the whole solar system.  It consists of charged particles of gas, and that gas has been superheated by some as-yet-unknown process to over one million degrees (that high, Kevlin, Fahrenheit, and Celcius are really all about the same), which is much hotter than the surface of the sun, which is about 5500 degrees C (10,000 F).  Even though it is so much hotter, it's dimmer because it's very tenuous and spread out.  

In addition to understanding the corona itself, the corona can tell us a lot about what happens on the sun's surface, as well as deeper inside, and can help us make future predictions for potentially electrical-grid-disrupting solar events.  In 1859, a massive solar storm known as the Carrington event disrupted telegraph communications, caused lines to spark and short, and even activated telegraph equipment that was disconnected from power.  Just imagine what something like that would do to today's electrical grids, computer systems, and satellites!

We have a few spacecraft that study the sun, including the corona, such as STEREO and SOHO.  SOHO has an obscuration disk that can be put into place to observe the sun's corona, but only as far out as three times the sun's radius, meaning we can't observe the inner corona at all -- except during a total solar eclipse.  

There are a variety of other interesting effects that are studied during total solar eclipses, such as the short-duration temperature changes, animal behavior, and how the temporary night-like conditions from a shadow that moves faster than the speed of sound across the surface of the Earth impact radio communications that bounce off the Earth's ionosphere at night.  Many of these projects involve citizen scientists who collect data to be processed by researchers.  There's a lot to do and see with eclipses!

Next post: #194 - Thursday, July 6, 2019 - In the Atacama Desert

Previous post: #192 - Sunday, June 30, 2019 - Southern Skies from Mamalluca Observatory

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