Inside of a dog...

2025/01/28: I took my first cut at Sharpless 308, the "Dolphin Head" nebula, from the community lot using a 105mm F1.4 Sigma lens, ASI1600MC, and SWSA. Polar alignment was OK, the air reasonably transparent but not perfect. This was the first 30-degree night following a serious cold snap, and it felt luxurious.

105mm F1.4 Sigma at F1.4
60x180s, Gain 300, -15C, Svbony Duoband filter, dark calibrated
SWSA. Make it big!

That's M41 at upper right, Delta Canis Majoris ("Wezen") at lower left. Lots of Lynd Bright Nebulae lace the field. There's a lot of physics going on this field. The central star of the blue bauble here is EZ CMa, a Wolf-Rayet star with a surface temperature of about 89,000 degrees Kelvin. The ultraviolet radiation from the central star as well as the collision of a fierce stellar wind with the interstellar medium produces the blue shell. Stars on the far left edge include Tau CMa (dominating the small cluster NGC 2362) and, just above it, 29 CMa.

You have no idea, and I am not inclined to describe, the number of versions and treatments I have been through with this image. It wouldn't hurt to double the exposure time. Or more. Through clearer air. Working so far left on the histogram is tough. (Hint: channel by channel noise control is sometimes useful.)

2025/01/29. A dark night in the Richlands with Bea and Jeffrey gave me a chance to try a broadband image of Rigel and environs. I set up in bright twilight and used a Bahtinov mask to focus on Rigel. That's the first time I've tried the mask with the 105mm; it works nicely. Then I let the 1600MC run until we headed home about 10:00PM. I tossed the first 30 frames and used the next 150 with the usual aggressive processing (BlurX, Starnet2, noise reduction, starless blend, faux flats, etc etc) to get this:

105mm F1.4 Sigma at F1.4
150x60s, Gain 139, -15C, IV/OR cut, dark calibrated
SWSA. Make this one big, too!

The red streak at top left is Sharpless 278 and is probably worth paying attention to with bigger glass. IC 2118 itself was discovered by William Herschel in 1786 or maybe by Max Wolf in 1891 or maybe in 1909. It's mostly dust doing a lot of forward scattering and reflection of Rigelian light. It might be a supernova remnant or it might not be -- there are an awful lot of mysteries here for a big, relatively easy target.

2025/02/03. Someone on AstroMart advertised a 400mm F2.8 Nikkor that had been fitted with a Teleskop-Express TeleFokus, a fine-focus rig more effective and less cumbersome than my belt-driven McGiver. I went shopping and soon found the right one advertised for 89 Euros, less VAT (about 12 Euros), plus shipping (35 Euros) or, y'know, somewhere around $145. I don't get that many chances to do deep sky stuff, so it wasn't the worst price if it helped assure sharp results.

I put one in my shopping cart and then looked up reviews (Cloudynights). I found user reports going back to about 2017. No one seemed more than guardedly happy. The good reviews included phrases like "pot metal," "sloppy," "looks and feels kinda home-grown," though most allowed that it did, in fact, work -- mostly. In fairness, the TS images (see above) look better than the one on the lens on AstroMart (which I would show you if I could find it again), so the product may be more refined now than when it was skeptically reviewed more than a few years ago. I unloaded my shopping cart and set to designing.

Over the last few days, my designs have gotten simpler and easier to build. I'm designing for one particular lens, not for whatever big glass a customer might have, so I can be a bit more focussed (so to speak) and not worry about universal fit (think pipe straps rather than collimation rings, for example). And since mine will be patently home-made, it doesn't matter much if it looks the part (hence GB-Weld to hold some stuff together and to serve as structural putty).

When the first load of parts came from Amazon, some of the key bits (the drive and lock bolts) were too damn small. EBay had an answer for that, and by the time I ordered the bigger pieces, a simpler, smaller design had taken shape:

Scale is aspirational; only the "active" ring is shown. Another will hold the bar (or captive nut) that moves the focus ring. In most (but not all) my cogitations, that piece is too simple to worry much about. Think of the pieces shown in these drawings as functional symbols rather than as blueprinted components. We'll see how things actually come together soon enough.

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