Sh2-155, Cave Nebula, UHC-S, 23 Aug 2012 (David Dearden)

Sh2-155, Cave Nebula, UHC-S, 23 Aug 2012

This is another of those objects you perhaps shouldn't do with a low-end 1-shot color camera, but I tend to try everything. The Cave took me a while to find. Finally I got a DSS image in Cartes du Ciel and was able to match some paired star patterns with what I could see in the guide scope image and star hopped over to this target. Chiller is starting at 12 °C. I've put the focal reducer on top of the UHC-S filter, so it is farther from the chip than usual. I believe this gives a little more reduction, so I'm calling it 0.5x. Using the plate solution, I get 0.57x (whereas with the reducer on the camera nose piece I get 0.63x). I had some trouble in processing: there were some prominent dust bunnies in this image that the flats did not quite remove completely. I don’t know how to increase the influence of the flats, so I resorted to just using the Photoshop healing brush on them. Something bad is going on in the bottom right of the frame; it looks as if the camera rotated, but it is only down in that part of the image, and I did translation+rotation alignment when I stacked. It doesn't look like coma, so I'm a little stumped.

Date: 23 Aug 2012

Subject: Sh2-155, Cave Nebula

Scope: AT8IN + 0.5x Antares telereducer (on top of the filter, not directly on the camera nose piece as I usually do.

Filter: Baader UHC-S

Mount: CG-5 (Synta motors)

Guiding: Orion ST80 + 0.5x Antares telereducer + DSI Ic + PHD

Camera: DSI IIc

Acquisition: Nebulosity 3.1.0

Exposure: 55x300 s

Stacking: Neb 3, bias included, normalize first, trans+rot align, 1.5 SD stack

Processing: crop, color balance, digital development with 1 level sharpening, levels & curves, saturation boost, GreyCStoration in N3. Astronomy Tools star color enhance, color blotch & deep space noise reduction, star size reduction, a little levels & curves, saturation boost all in CS6.

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Status	Basic success
Started	...
Astrometry.net job	8654483
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