Staring @ the Sun, 119

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Getting Closer to Totality

03/20/2024 When we last chatted on this part of the blog, I was about to go shoot Geminids. Worked out well enough. I got an APOD out of it, so I'd say that was at least "well enough." Go check it out over on the stargazing section. Here we're talking about an eclipse. Actually, I'm kinda thinking out loud. Either bear with me or just skip around and look at the pictures. Here's the first corona forecast (from 3/21):




No, it was not a good idea to put two cameras with long lenses on the SWSA and let one counterbalance the other. The weight and the long moment arms meant that every little thing set up lots of vibration, made finding the Sun and focussing on it difficult, and so on. Every breath of wind shook both cameras badly, and Texas in April might have a lot of breath. Resonance with the mechanical curtain in the R6 threatened the EOS-M's take, and centering the Sun in one often lost it in the other.

After today's dismal test, I took the mounting hardware apart, turned the Dec slow-mo gearing around so I could mount the EOS-M/700mm directly over the RA axis instead of off to one side, and I'll find another solution for the R6/500mm. I also discovered that I couldn't read the settings on the EOS-M with my usual reading glasses (stronger ones enroute... and stronger ones are here; 5.00 does nicely).

Later that night, tests on the Moon with the EOS-M alone showed that the new mounting arrangement is rock steady for video. MLVApp is good and powerful stuff for converting dual-ISO data into useful video, but be prepared for a long render (5-6 hours?) when working with just a few minutes of data. I'm thinking 200/1600 at 1/1700 second and F6.3. That's about one stop darker on the slow end of the dual ISO than 2017's video, which I have watched several times (it was ISO 140, HDR mode, at 1/1000 and F4.5) and at least as bright on the high end. I'm more concerned with burning out the 2nd and 3rd contacts than with underexposing, so that should have me covered. With MLVApp and such high bit-depth data, I ought to be able to do just about anything with the footage.

Since I'm dialing the R6 back from 1000mm to 500mm, it doesn't actually need to be on a tracking mount. Cheat second contact a little toward the left side of the frame and let it roll. That means that just a flat plate hosting a ball head (or the original alt-az head from the SWSA for fine motion control [yes, use that]) would suffice. I went looking for a commercial product as a sanity check. Plates for ground-level photography are a thing, and many are pricey. Why? I aim to make mine, of course, to fit and further strengthen the shipping box into the bargain. Since I won't be tracking the R6, and will eliminate the 2x converter, I'll cut the 1/2 second maximum exposure back to 1/4 second and probably select ISO 200 rather than 400. Considering the shorter maximum exposure, I've cut the intervalometer to 1 second intervals [which makes less difference than I imagined it might, but done anyway].

For mid-totality: hundreds of cycles of 1/2500 1/500 1/100 1/20 1/4 at ISO 200 (400?) RAW would give me a lot of data, and that's how C2 is configured now. [Don't sweat the difference between 200 and 400 ISO, 'tis but a nudge of the exposure slider during RAW conversion.]

For 2nd and 3rd contacts: 1/4000, ISO 200, CRAW. No intervalometer needed, just push the remote button to "on" and let it run for as long as needed. It can run without buffering for at least 25 seconds in CRAW mode, maybe forever, and the buffer clears in a second or two. That's how C1 and C3 are configured.

The 6D will have the 12mm full-frame fisheye. It will be on a monopod. Wide-open, prefocused, ISO 800 or 1600 and whatever seems right in the way of exposures. Just count on experience and try not to go crazy in the moment.

The 360X2 I bought for rowing will be on its own tall, invisible selfie-stick. Just turn it on, run it up the mast, and see what it gets. Take a walk with it among the assembled before and after totality, too.

The Fujifilm X100T, which will be my walking around camera in Texas, will be around my neck just in case. I have no plans for it during totality, but you never know.


03/21/2024. The flat plate came together. Scrap pine, a drill press, a chop-saw, a sander, and some polyurethane. Pix and more rehearsals to come. The carbon tripod has three, not just two, spread settings. The middle setting is just the ticket: sit down behind the cameras and go all "omm" until the show is over. Either pack my cane (a seldom-used souvenier of hip replacement), or make sure the 6D's monopod is strong enough to help me up (I had no trouble shooting the lunar eclipse down below, and that's without umbral adrenalin).


eclipse kit

03/25/2024. This works! On the right: Canon EOS-M on a StarAdventurer tracking mount. The EOS-M runs Magic Lantern firmware and will be shooting raw 4k, 24fps video with 3-stop dual-ISO readout, a combination that ought to yield at least 15 bits of dynamic range. Mounted to that camera on a SmallRig bracket is a robust powerbank because the M's tiny battery tends to run down quickly and might do so at just the wrong time. It's mounted on a budget but very stable Sirui carbon tripod. On the left, a Canon R6 on a fixed mount with preset exposure modes: electronic shutter 20 fps CRAW for diamond rings and Bailys beads switchable with one touch to electronic first-curtain shutter for a 5-shot bracket to be repeated hundreds of times during totality. Both cameras are looking through identical 500mm F6.3 Rokinon mirror lenses (thanks eBay!). The EOS-M's lens is teleextended to 700mm for improved image scale. After allowing for sensor size and video cropping, it will be working at a 35mm equivalent focal length of around 1500mm. I made quickly removable bracketry for Baader-film solar filters on both lenses. Each lens is fitted with a belt-driven, manual fine-focus knob (one of those standing-in-the-shower designs that actually worked out). What could possibly go wrong? [Don't answer that.]

After the trial above, I added a 3-inch micro-pier to the R6's plank:

kit a


Detail of the EOS-M set-up:

kit b

See, "Ha! Late-breaking news" down below for more about that tripod. This rig, too, is going onto a more compact mount. Also, it's way too easy to accidentally turn that tracker on. One of the middle batteries now has a piece of electrical tape blocking the negative pole. "Remove before flight," as it were.

What the R6 saw:


Click to embiggify

That's from the R6/500mm through Baader solar film, 1/2000 second at ISO 200, pulled considerably using Photoshop curves and rebalanced 70,0,-70 (CMY). You can accomplish much the same thing by opening the raw file with color temp normalized for 50k and pulling the exposure about 3/4 stop. The white line represents the edges of the full frame. It's not necessary, but it might be advisable to crank the Sun a little back to the left halfway through totality. The Sun will drift about 1.2 degrees (2.5 times its own diameter) left to right with practically no change in altitude between diamonds (just six arc minutes). Start a little left of center (as shown here), and just nudge it back a bit at the two minute mark. You'll feel better. If you get busy and pass on that, it's not a disaster. Note that focus in this demo was not perfect, but it still cleaned up well. The sharp edge of the Moon, especially the sharp horns of the crescent Sun, will make a much better target.

When I went out to retrieve the kit late this evening, I discovered that I had left the EOS-M on. After seven hours, the battery pack still had 38% power remaining. That's good battery life.

I am very pleased with the plank mounting. If I'd tried this weeks ago, I might have opted to leave the tripod home. That would make for much simpler and more compact packing. I'm not making a change that radical just a few days before time to ship toys to Texas. If it works as well as I think it's going to, then I'll refine the kit with the possibility of Spain and Australia in mind. But do let's try not to look beyond this year for now, 'K?

Ha! Late-breaking news: I built a second plank mount because that 24x12x8 box has got no room left for anything. Like clothes. Or socks. Eclipse chasing without a tripod? Sure, why not? No time like the present to try out a new idea. The original, larger one now goes with the video camera with no "micro pier" because the Williams alt-az support and SWSA leave plenty of room to see the rear screen. The micro-pier and original SWSA alt-az support still go under the R6 but on a new, smaller plank. Both planks go in the FedEx box, and the tripod stays home. God help me.

During the early morning hours
of 3/25, the Moon went through a penumbral eclipse. Here's the view just prior to the beginning of the eclipse using the 500mm at ISO 200 and 1/2000 second on the plank mounting. Tell me that lens isn't sharp!


G'head, make it bigger.


Here's the Moon cropped from that frame at full resolution:


The color is a little off. Easily fixed, of course, but a bit of a surprise.

A side by side comparison of the Moon just before the beginning of the eclipse and at maximum depth two hours and change later seemed worth doing. Same lens, same exposure. The Moon has been rotated to match the orientation of the earlier image and the histograms normalized on the brightest terrain near the northern limb farthest from the Earth's shadow (500mm F6.3 Rokinon, 1/2000s, ISO 200, Canon R6, using the "plank" mount above.)


eclipsed moon

Sure, sure. Click it. Why not?




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                   © 2023, David Cortner