I've visited the Eagle many times, but this time decided to use the coma corrector and get as much magnification as possible. Synched on ν Oph and acquired with the PicGoto. Very good conditions except it was quite warm (CCD at 25 °C). Got outstanding guiding performance for once, but something went wrong and froze the acquisition after I retired, so I only got 28 subs. I kept noticing aberrations around the edges of this image as I was processing, then finally realized I had made the stupid mistake of leaving the focal reducer on along with the coma corrector. So for at least two reasons this image could have been much better than it turned out. I also learned a couple of things in processing. There is a critical value of the smoothness parameter in StarTools’ Track module at which you lose real detail; only one step makes a difference. Also, I found adding a Contrast operation as the last step in StarTools really brought out details (contrast, not surprisingly!) without introducing much noise.

Date: 19 Jun 2015

Subject: M16, Eagle/Star Queen Nebula

Scope: Orion ST-80+Antares 0.5x Focal Reducer+High Point Scientific Coma Corrector (duh!)

Filter: Baader Fringe Killer

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

Guiding: 9x50 Finder/Guider + DSI Ic + PHD 2.5.0 (Win 7 ASCOM)

Camera: DSI IIc no cooling (about 25 °C)

Acquisition: Nebulosity 4.0.2, no dither

Exposure: 27x300 s

Stacking: Neb 4.0.2, bad pixel map, bias included, 33 flats, histogram match, deBayer & square. DSS 2x drizzle, 1.5σ κ-σ stack.

Processing: StarTools 1.3.5.289 Crop; Wipe: 83%; Develop: 74.99%; HDRptimize; Color:Scientific 250%; Deconvolute 5.3 pix; Life:moderate; Track 9.4 pix, smoothness 88%; Magic, shrink 3 pix; Contrast. Photoshop CC 2014 + Carboni Astronomy Tools Deep space nr; Increase star color; Make stars smaller; Color range select, lighten, and desaturate to remove some star halos; Liquify/pucker on many stars; Layer masked space nr; Astroframe.