Celestial hemisphere:  Northern  ·  Constellation: Andromeda (And)  ·  Contains:  NGC 891
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NGC 891, "Outer Limits" Galaxy, UHC-S, 18 Sep 2015, David Dearden
NGC 891, "Outer Limits" Galaxy, UHC-S, 18 Sep 2015
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NGC 891, "Outer Limits" Galaxy, UHC-S, 18 Sep 2015

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Description

Another attempt to improve an image by going to 600 s subframes. This was also a first attempt to improve guiding by using 0.5 sidereal as my guiding rate, rather than 1.0 sidereal as I always have previously. My reasoning was that east-weighting the mount should work better if the mount is always moving west, as it would be at this guiding rate, rather than momentarily stopping, as it would at 1.0x. My RMS values were lower than any I have achieved recently, so maybe this was a success, but conditions were also much better than average. The sky was perfectly clear and transparent, with no wind. Cooler than it has been, so the camera was at 15 °C. The galaxy came out excessively red for some reason, so I processed with a bit different color management than usual.

Date: 18 Sep 2015

Subject: NGC 891, “Outer Limits” Galaxy

Scope: AT8IN

Filter: Baader UHC-S

Mount: CG-5 (Synta motors, PicGoto Simplificado)

Guiding: 9x50 Finder/Guider + DSI Ic + PHD 2.5.0.1 (Win 7 ASCOM)

Camera: DSI IIc, no chiller CCD 15 °C

Acquisition: Nebulosity 4.0.2, no dither

Exposure: 33x600 s

Stacking: Neb 4, bad pixel map, bias included, 33 flats, OSC neb filter, match histograms, deBayer & square, trans+rot align, DSS 2x drizzle 1.75 average κ-σ stack.

Processing: StarTools 1.4.305 Crop; Wipe 75%; Develop 83.47%; HDR optimize; Color: scientific, 200%, RGB ratio, CIELab Luminance Retention; Deconvolute 6.0 pix; Life: Moderate; Track 6.2 pix, Smoothness 89%; Magic: shrink 2 pixels. CS6 Astronomy Tools deep space reduction; make stars smaller; debloat stars with liquify/pucker filter; Astroframe.

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NGC 891, "Outer Limits" Galaxy, UHC-S, 18 Sep 2015, David Dearden