Lunar eclipse 2022

The last lunar eclipse I had clear skies for came back in 2014. I did a bit of astrophotography for that one, and managed to put together a crude animation of the event. It didn't turn out great, because I had no plan going in, but was a neat proof of concept. For the 2022 eclipse, which May 15, I planned to do better.

Except that I forgot about it completely, until Lisa stuck her head into my office and asked if I was interested in watching the eclipse, which had already begun. Argh! There wasn't time to set up my telescope (762mm focal length!) and calibrate its equitorial tracking, which meant I would not be repeating the animation trick this time around. So instead I settled for using my Canon FD 500mm f/8 reflex lens (converted to EOS mount by yours truly) on my tripod-mounted 7D. The results of this setup were... okay. Adjusting the camera on the tripod was a real pain. You forget just how convenient an equatorial mount is for making tiny observational adjustments until you don't have it. The 500mm lens I used is, in fact, a small telescope. Emphasis on small. Still, it performed as well as can be expected and respectably documented the event. Next time, though, I'm going to plan better...

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Chicken Ranch Central

Lunar eclipse!

The morning of Tuesday, April 15 saw the first of four lunar eclipses slated to occur over the next two years. That's celestial mechanics for you--like a Venusian transit of the sun, these things come in groupings. Unlike Venus passing in front of the sun (which happens at century-long intervals), lunar eclipses are comparatively common. But not that common. The last lunar eclipse visible from North America, in 2010, didn't turn out so well for me. Because of the chance of clouds at any time, I was determined to take advantage of the opportunity this time around.

Several things are different now than they were back in 2010. For one, I have a different mirror in my telescope, which I'm still sad about. The second is that I've figured out why there was so much diffusion in my 2010 photographs--the plossl eyepieces I use for visual observing introduce field curvature, which causes the edges of the image to be out of focus. If I'm ever to get serious about eyepiece projection astrophotography, I'll need to invest in flat-field orthoscopic eyepieces. I've also got a better camera--the Canon 7D--and have learned I can use a telextender to double the telescope's focal length, thus making the moon fill the frame of my camera. Finally, I've got a rock-steady Orion Atlas equatorial mount for my telescope, a significant upgrade from the 1970s era pier GEM mount that came with the scope.

Unfortunately, I wasn't feeling all that well, and wasn't up to doing much preparation. And I'm still not entirely familiar with the Atlas mount, so wasn't able to get it to track the moon very accurately (although the electronic controls worked very nicely and allowed me to position the image precisely). I moved the mirror up in the tube so I could shoot at prime focus with the camera. Ideally, when I did this, I should've collimated the scope to make sure the mirrors were in good alignment to ensure the best possible image. But I was tired and sickish so I didn't.

As for the weather, this time around I was not plagued by clouds. The sky was crystal clear, in fact, and it got pretty darn cold for Texas in April--down to the lower 40s. Brr. Which should've meant great views, but it didn't. There was a good bit of wind on the ground, and a lot of turbulence up high in the atmosphere, making the moon's edges waver and forcing me to adjust focus regularly simply because the "boiling" effect of the atmosphere made it impossible to be certain I ever nailed focus. None of my photos turned out as sharp as I'd have liked because of that, but overall it wasn't a bad effort. The 6" Meade 645 f/5 Newtonian has a focal length of 762mm, and for most of the night I used a Vivitar 2x telextender, which essentially turned the scope into a 1524mm f/10.6 lens. I had to remove the telextender during total eclipse, though, because the moon was too dim to shoot without those two extra stops of light--and even then I cranked the ISO up to 3200 (which introduced significant noise to the image). The good news is that I'm progressing with my competence in astrophotography. The bad news is that I clearly have a long way to go. I combined 30-something images into the animated gif above. You can see a progression of the original still images below. Hopefully, by the time the next lunar eclipse comes around, I'll have mastered the Atlas' tracking and be able to shoot totality using much lower ISO and longer shutter speeds.

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The eclipse that wasn't

So yesterday I checked the weather reports and read the tea leaves, at which point all indications were pointing toward perfect observing conditions for the 2010 lunar solstice eclipse. Neat-o! Lunar eclipses aren't all that uncommon, but I was jazzed to attempt some astrophotography of the event. I dimly recall attempting something similar 20+ years ago with a film camera, but like all my astrophotography efforts back then, classifying the results as "failure" is being generous.

I set up my Meade 645 6" f/5 telescope in the back yard, and spend maybe half an hour leveling it and getting it into polar alignment, more or less. Then I adjusted the finder scope and collimated the mirrors, so as to get the best possible images. After the sun went down and the full moon came up, I attached The Wife's Canon 50D camera to the telescope via a T-mount camera adapter, with a 25mm eyepiece in the adapter barrel. Using the camera's Live View feature to get accurate focus, I shot some test images, and was disturbed by the following:



Yes, the center is certainly sharp, but what's with that halation around the edges of the moon? I tried different size eyepieces. No difference--the center remained sharp, but the further out from center the fuzzier the image got. After about an hour of failed troubleshooting, I tried one last gambit. My telescope is designed to act as a lens for the camera, with no eyepiece in between. This is called "prime" photography. The downside is that I'm stuck at one focal length--that of the telescope--and can't swap out the magnification as with eyepiece projection. Also, the primary mirror of the 'scope has to be moved forward in the barrel several inches to make up for the focal difference between the human eye and camera, which means that in this configuration, it is useless for eyeball astronomy. It simply won't focus for human viewing. Still, I thought it worth the hassle if I could get some sharp eclipse images--and if the halation was still present, I'd know the fault lies with the mirrors of my telescope, or perhaps my crummy collimation. Here's my first test shot using the telescope as a prime lens:



Wow! Quite a difference, eh? I don't think I've ever taken an astrophotograph that sharp before. I was happy. Yes, the moon would be smaller this way without the eyepieces to magnify, but I could tolerate that in exchange for, you know, decent images. I was ready for the eclipse!

Then the high fog rolled in. Low clouds, whatever. Streaming up from the south, the misty stuff was like sheer curtains billowing across the moon, obscuring it one moment before clearing out for half a second of almost-clear viewing. The forecast had called for generally clear skies, with maybe partial clouds later in the evening. Nobody had said anything about this. I vowed to wait it out. Surely it would clear out, right? Around 12:30 a.m., just as the moon was entering the umbra of the Earth's shadow, I tried to shoot between the clouds, or at least through the thinnest areas blowing by overhead. The results were uniformly disappointing. Even in the thinnest sections too much light was lost for good exposure--below is the best capture I managed, and even this--over-dark though it may be--was brightened up considerably in Photoshop:



On the bright side, I've become a believer in my telescope's ability to take sharp astronomical photos, even if it wasn't able to show off with the eclipse. My particular telescope is a short-barrel Newtonian, designed back in the '70s for wide-field, deep space astrophotography. We've got plenty of clear winter nights coming up in the next few months, so hopefully I'll have an opportunity to turn it toward the Orion Nebula or the Pleiades and other cool celestial spectacles. We'll see if my sharp lunar image above is a fluke or if I replicate that focus on a regular basis.

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