Astrophotography diagnosis of NGC 6085: Noise / underexposure, sensor tilt and 2 others

Tough conditions for this target: an 85% Moon combined with a broadband L filter on a faint galaxy field is about the worst possible pairing. Lunar luminance drowns the SNR and drives the measured oriented gradient (23% amplitude). Galaxies in a group like NGC 6085 need a dark sky and lots of signal; here the e_margin of 1.47 confirms an under-exposed background swamped by sky glow. Move this target away from full Moon (illumination below 30%) to gain several magnitudes of contrast, or reserve bright-Moon nights for emission targets with a dual-band filter. As is, processing spends its time fighting the background rather than revealing the galaxies.

The ED APO 127 f/7.5 at about 950 mm with the ASI2600MC gives comfortable sampling (center FWHM 2.37 px, well above the floor) and a wide field suited to a galaxy group. The Wave 150i tracking is excellent (center elong 1.02, scattered PA). Two points: a slight sensor tilt degrades the right side (FWHM 3.42 vs 2.65), to fix by squaring the optical train to even out the field. Above all, the L filter + galaxy target combo demands lots of exposure: 20x60s is far short. Move to 180-300s subs and aim for several hours total. The setup is healthy; it is the acquisition strategy that under-uses the instrument.