A beautiful moonless night, so I decided to go back to one of my favorite and most-attempted targets, M81. Because I'm routinely doing 600-s subframes now in Hα, I decided to try to go deeper with M81 by using 600-s subs and the UHC-S filter. Finding was via synch on α UMa followed by PicGoto acquisition. I had some trouble initiating guiding; calibration went OK, but then the guide star started drifting off in Dec. I think my Dec gear clutch was just loose. Imaged up to the meridian, then re-synched with Astrotortilla and reacquired and imaged until dawn. I was thrilled to pick up what appears to be a small satellite galaxy at top center. I wasn’t sure that wasn’t an artifact, but now I’ve seen it in others’ images so it must be real.
Date: 16 Feb 2015
Subject: M81, Bode’s Galaxy
Scope: Astrotech AT8IN+High Point Scientific Coma Corrector
Filter: Baader UHC-S
Mount: CG-5 (Synta motors, PicGoto Simplificado)
Guiding: 9x50 Finder/Guider + DSI Ic + PHD 2.4.1 (Win 7 ASCOM)
Camera: DSI IIc no cooling (about 0 °C)
Acquisition: Nebulosity 3.3, no dither
Exposure: 41x600 s
Stacking: Neb 3.3.2, bad pixel map, bias included, 33 flats, histogram match, deBayer & square, trans+rot align, 40-60% median combine.
Processing: StarTools 1.3.5.289 Crop; Wipe; Develop 87.49%; HDR
ptimize; Color: Scientific, 300%; Deconvolute 2.5 pix; Track 3.5 pix; Magic: 1 pix. Photoshop CC 2014 + Carboni Astronomy Tools Deep space noise reduction; Increase star color; Layer masked unsharp mask for dust lane enhancement; Astroframe.
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