Let's Get Serious
01/10/2023. The SWSA can do real photos, so let's get down to making the most of it. Hardware for a geared-down focusing scheme for the 500mm Rokinon and 105mm Sigma is enroute, and I'm waiting for the Moon to get out of the way for some more ambitious targets. The extended forecast calls for clear weather on Saturday morning, 1/14, so I may get a chance to photograph a comet soon.
In the meantime, more plausibility checks: I tried to duplicate and perhaps improve on last night's Pleiades photo. I aligned the mount the same casual way, by lining up on Polaris without regard to the reticle, but I moved a little farther north to mostly avoid treetops, used a tripod collar shimmed with brass instead of electrical tape, and selected ISO 12,800 rather than 3,200. With this many frames to average, noise is not a first-order concern. I increased each sub-frame's exposure from 15s to 20s and collected 193 frames before clouds moved in for good. That's a little over 97% of yesterday's total exposure at 4x the gain. At F6.3, the complex but faint nebulosity will take some exposure time. This is moderately cropped, because otherwise gradients are distracting (use a flatfield, whydoncha). It's still not a killer Pleiades image, but as an engineering test, it's useful.
196x20s, ISO 12,800
(Make it large.)
Tracking is not a problem. Tomorrow's mail ought to include timing belts, pulleys, a couple of knurled knobs, and some always-useful Arca pieces to hold all the parts together as a geared focusing kit. A few "Lens Bands" to hold focus will follow soon, and so will some crimp clamps to allow me to make custom-length timing belts as needed. I need to put the full eclipse kit on the SWSA just to see if I need to rethink that plan wholesale. My (limited) experience with the mount says it should work as long as I keep my hands off it while the shutter is open. I need to see if I can reduce the shakiness in the outfit (preferably without indulging in the Williams base which we all know is coming sooner or later). In its present form, the stars jitter around like mad when magnified for critical focusing. Between the long lens and the focus magnification, that's about a 100x view, so I am not surprised. The shakes are not intolerable, but they would be better gone. Or reduced.
1/11/2023. I do not generally advocate having a couple of glasses of Malbec before descending into the machine shop to cut aluminum, drill and tap holes, and fit dovetails, pulleys, and timing belts into an ill-conveived widget, but I am here to testify that it does sometimes work out. Tomorrow, after verifying that I still have my original complement of fingers and eyeballs, I'll show you the finished product. It helps that I've been sketching and overthinking it for days; cutting metal at last was a positive relief.
I am pretty sure this gadget will make all the difference for focusing the 500mm F6.3, and it may help with the 105mm F1.4 which is demanding in its own way.
1/12/2023. The geared-down focuser's design put me to sleep several nights and came together very nicely. I'll need the clouds to move along before I can give it a try under the stars. It's probably a work in progress, but this is progress and it does work.
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