The Starry Night, 171

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6/29/2016. The A-P Mount
is a tolerant beast, but balanced loads are better than unbalanced. It (finally) occured to me that I could avoid the need to repeatedly unclutch the drives and balance this and that before doing the bubble-level dance to initialize the mount in "Park One" if I would just take a picture of each outfit in "Park Three" after balancing it once. If I recorded the position of counterweights (for RA balance) and fore and aft OTA position (for Declination), then I could just pick whatever optical tube assembly was appropriate on any given night, clamp it to the mount, and slide things around until the outfit resembles the picture. That would save some time and a fair amount of hassle. So my aim is to keep a collection of photos here for reference. If I were organized, I'd also include focusing positions and workflows for this and that or at least some links to such things. It's a worthy ambition.


10-inch F4 Newtonian:

10-inch Newt









90mm Solar Frankenscope:







PixInsight: see link.

PemPro: Key item is to launch Meade Envision and get the DSI-Pro to respond, then close Envision and run PemPro. Drivers on the Dell 820 are configured for the DSI to plug into only one of the two available USB ports on the right side of the computer. Experiment and take note of which one! Run the calibration wizard and take periodic error data in one session unless you can take down and set up without touching the DSI.

PHD: (tk, also Losmandy variation)


Focus Positions:

Rokinon Lenses: see link.

AT10RC, F8, CCD, CFW-10: use 2-inch extension tube, set focuser scale near 2.5 cm.

AT10RC, F4.8, CCD, CFW-10: just a whisker out from full-in.

AT10RC, F8, 6D: Short, wide camera adapter behind a 2-inch mirror diagonal, no other extension tubes. (Try Feathertouch and an extension or A-P snout w/o diagonal.)

AT10RC, F6, 6D: Put AT 2-inch flattener / compressor on short, wide-mouth adapter and use minimal out-travel. Images suck, however.

AT10RC, F5.3, 6D: see here but recheck practicality of flatting and inspect PSF's.

AT10RC, F8, video camera: (tk)

AT10RC, F15, video camera: (tk)

AT65EDQ, 6D: Near 5.5 cm.

AT65EDQ, ST2000XM: (tk, untested)

TMB92SS, 6D w/Orion flattener & 10mm extension (OTA long): near 4 cm.

A-P, 5" F6: tk

A-P, 5" F4.5: tk

10" F4 Newtonian, 6D: insert Feathertouch adapter, then Baader corrector. Focus is about 1/8 inch out from full-in on the Feathertouch (leave the stock focuser at full-in).*

* Is there enough in-travel to use the Feathertouch adapter on the 10" F4 Newt? That would solve so many problems! If necessary, try turning the knurled ring off the 2-inch adapter for a few extra mm of in-travel. [No, there was not room for the Feathertouch adapter. Close, but no. Yes, I could turn the knurled ring off the 2-inch threaded adapter to let it move farther in, did, and yes, now the 6D comes to focus some small distance out from full in while using the Feathertouch adapter. So! Focuser issues solved on the Newtonian! Almost: at full-in, the bottom of the focusing tube intrudes into the light path as revealed by a notch in out of focus stars. This may not be an issue at the actual focus position, but it probably is, and if it is, it's nothing a chop saw or the lathe can't fix. Lop it off. Lopped it off because I could. There. I've been working on this since August 2014. Gracious.]

Other OTA's:

The 6" F5.9 achromat is really a visual instrument. The Baader Fringe-Killer helps its photographic performance but not as much as it helps its visual performance. In photos, blue-bloat both with and without the Fringe-Killer is objectionable. Focusing with the stock focuser is really not up to top-shelf astrophotography either. It's a nice RFT (remember that that's why it's in the kit!). It's easy to get spoiled, no?



Collimating the RC: see link.

Purging moisture from the CCD. (tk)

Remeshing the A-P mount's gears. (tk)



My deep-sky photos are made with a variety of sensors and optics. Deepest images usually come from a SBIG ST2000XM CCD behind a 10-inch Astro-Tech Ritchey-Chretien carried on an Astro-Physics Mach1GTO. The CCD is equipped with a CFW-10 loaded with Baader wide- and narrow-band filters. Camera control and guiding are handled by Maxim DL 5.12. A Canon 6D and a modded 50D find themselves mounted behind an Orion 10" F4 Newtonian or a 92mm Thomas Back refractor or a tiny but mighty AT65EDQ refractor, sometimes with Backyard EOS in control and PHD Guide keeping things on target. Really widefield photos are often made using the 6D and various camera lenses and an iOptron Skytracker mount. PixInsight does most of the heavy lifting in post-processing — alignment, stacking, gradient removal, noise-reduction, transfer function modification, color calibration, and deconvolution. Photoshop along with Focus Magic and a handful of other plugins get their licks in, too, especially when polishing for the web.


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                   © 2016, David Cortner