The Starry Night, 263 :: home :: |
Waiting for the Comet.
The solution to holding two pieces of fast glass turns out to be simpler, cheaper, and smaller than anything I imagined in the shower or while waiting for sleep. I've got a very short (~5.5") piece of Losmandy DMM plate here. Way out toward one end, I've put a long Arca clamp intended for the 400mm Nikkor. (It's not aligned with the plate nearly as well as I would like. How in the hell did I miss that far? Shouldn't matter, but Obsessives R Me. There's room for a second cut at this.) At the other end of the short plate, I've put a 3/8-inch hole countersunk for a socket bolt to which the heavy-duty Sirui ball head attaches. The ball head will hold the 105mm Sigma and anything less. A dry run to confirm clearances reveals that the 400/105 combination is mighty. This plate will also work for less massive arrays (105/25, for example) on the SWSA. That may require a few more bits of hardware, but nothing special. Worry about that another day. All this was more of an adventure than strictly required because the spindle on the drill press has become loose (the chuck simply falls off when confronted by any resistance). I had to complete some of the boring as if I were cutting threads, turning the bit by hand. The net is out so I can't look up the proper fix for this. My improvised shims have been useless. A quick look via cell phone hotspot says I'd not be far off with my wildass thoughts of using SuperGlue on the spindle. (Had a beer, attacked the spindle with a Scotch pad for cleaning and smoothing, SuperGlue for holding, and pressed it all together for a few minutes. Then I fixed the damn misaligned Arca-clamp. I highly recommend a beer when approaching this sort of thing; not wine; and definitely not more "industrial" lubricants until done.) 2024/8/26. Yes, I have been dreading demounting the 10-inch (and finding a place to stash it) and cleaning up the A-P mount. But I finally got started on all that yesterday. The air was good, so I took time out for some sungazing. Late last night I went "slumming" with the SWSA and an hour-long photo of M13.
The photo worked out well enough, but 250 raw frames just about choked my computer during the image integration phase, and it took a ridiculous amount of time under the stars to find M13 by eyeball. (How hard could that be? I am out of practice. Also, setting the camera for too-long an exposure while using it as a night-vision scope via exposure simulation can get a bit wonky -- faint stars appear indistinguishable from bright ones. Frame with exposure set to 1 second or so.) Both the choked computer and blind eyeball issues would benefit from getting the A-P into use. Longer subframes could reduce the number of subs required, and many more targets will be available when I don't have to eyeball them through the viewfinder first. Also, work out how best to flat the 400mm. My first try was not good. The image above is uncalibrated, working with data deBayered by Pixinsight straight from the Canon's .CP3 files without first converting to .XISF or applying any corrections. GraXpert and SetiAstro's ADBE each had a cut at the finished stack in Pixinsight as did ProDigital's Astroflat utility in Photoshop. I tried shooting the dark nebulae north of Cygnus. It might have worked if I had remembered to turn on the tracking motor. Here's a stack of 147, fifteen-second exposures as the stars sailed by.
08/26/2024 part two. Oh, hey. Only I need to know this, but the best way for me to remember it is to write it down here: the electronics for the A-P mount are boxed up and tucked into a Craftsman tool bag so that they can safely ride with a counterweight and counterweight extension. There's a spare USB3 cable in there, too, just in case. I've been cleaning, rearranging, reorganizing, and as we all know, that is an invitation to frustration and to chaos. The 7nm h-a filter I use as a really good IR rejection filter in the solar kit is in a plastic case in the fancy tool chest o'drawers with other filters and eyepieces where the damn 12mm Nagler is supposed to be but is not [still hunting].
9/01/2024. Russel Cronan's "BlurXterminator" was impressive in its first iteration, but I didn't pull the trigger. After seeing some examples of what the second coming can do and seeing that the 400mm Nikkor is immensely capable though challenging to focus and can show some odd star shapes, registering a copy became a no-brainer. Holy shit this is good stuff! Most examples may not be gobsmacking at web resolution, but once the parms are adjusted to the source material (took a dozen experiments, still refinining), the results at full resolution and anything close to it are simply astonishing. For the moment, these are the settings I'm using:
There is no guarantee that those are optimal or even well-understood. But the results are impressive. For one particularly challenging field (Barnard's Snake, B72) with strong gradients and a relatively weak signal, this worked well entirely within PixInsight:
Play with it some. It also works very well with (some) solar images. Successes and notes will eventually appear over on the "Staring at the Sun" stage. For the moment, note that a key is to set nonstellar parms. I've had good luck with something like 7.0 and 0.6 followed by tweaking for contrast in Photoshop. The best starting points are up for grabs: let BlurX do it all? start with a PS-adjusted file? start after an ImPPG pass? Each has worked well for particular images. One workflow would be great, but seems unlikely at first glance.
9/02/2024. Another (cheap) try to make things portable. I've reassembled the A-P on the porch on the historic Linhof tripod, cleaned everything up, packaged this and that for travel (even if just over to the community lot), and I am impressed with both its solidity and its inertia. I don't want the expense and discomfort of pulling a muscle while horsing the mount to and from the car and to and from an observing site. I especially don't want to damage the A-P by losing my grip on it. It's not heavy -- 28 pounds claimed, plus 10 for the counterweight bar, more for a saddle, adapter hardware, and polar-scope, so call it 45 pounds on the hoof. But it is awkward. What if I used a folding garden cart to move it and its accessories (electronics, batteries, computer, cameras, primary OTA and guide-scope) in a single commute? It wouldn't save me a trip down the steps. But it would mean one trip to and from the car on site, and a more organized trip to the car from where ever it's eventually domiciled. I went shopping on Amazon, reviewed a dozen carts, then found the same product remaindered on eBay. We'll see how it goes later this week.
09/05/2024. It worked out very well! I took the heavy-duty kit over to the community lot, parked near the south end, and used the cart to transport the A-P and all its components and required bits farther on to a good view of the southern sky. The sky was pretty dreadful, and it got worse later in the night contra forecasts, but the cart and kit worked great. Focusing both the 400mm F2.8 and the 105mm F1.4 are vastly easier and more accurate on the rock-steady A-P than on the maybe-it'll-do SWSA. The next day, I cleaned up the tripod, repainted the top-end metal bits, sanded down the top of the tripod that mates with the A-P adapter (it sticks, stuck?) to make it all easier to use next time. It looks good, and we'll see soon how well it works. I've topped off the li-ion battery pack. It went from 13.2 to 12.5 during early slewing steps, then held that voltage for hours; a bigger battery and a step-up transformer to keep V at 13.6 or so would be good but clearly not required in the DSLR, tracking-but-not-guiding mode.
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© 2024, David Cortner