Astrophotography diagnosis of NGC 6960: Sensor tilt

Excellent conditions for this target: Bortle 2 sky and the Moon below the horizon during the exposure (90° separation, illumination irrelevant here since it had not risen). No lunar gradient expected, and the very dark background is ideal for capturing the faint filaments of the Veil. The small measured plane gradient (16%, oriented ~177°) is consistent with the Milky Way / field nebulosity rather than light pollution: nothing to fix upstream, a simple background extraction in processing will handle it. This is a reference night, worth using it to stack plenty of integration.

Coherent setup: the ASI585MM Pro (1/1.2" sensor) with a 1.70° wide field frames the western part of the Veil around 52 Cygni well, and it is properly centered here. The sensor runs at -11.5°C, healthy cooling that limits dark current. In Hα (narrowband), the low background/black-point margin (e_margin 1.85 at 300s) is NORMAL and does not indicate underexposure: the background sits just above the black point with no dark clipping, exactly what you expect from a narrow filter under a dark sky. Gain 252 is high but the bright star does not clip dramatically; you could test a more moderate gain (unity) to gain dynamic range on 52 Cyg, otherwise 300s is a good compromise.