Astrophotography diagnosis of SH2-114: Tracking drift and backfocus error

Excellent conditions: Bortle 2 and a moon at 0.8% illumination, so essentially no lunar contribution despite its 40.5° altitude and 50.3° separation. The measured background confirms it, with a plane gradient of only 1% amplitude and zero azimuthal anisotropy. Under such a dark sky, a faint target like SH2-114 is perfectly workable in broadband, including on the G filter. The background-to-black-point margin e_margin of 2.2 stays low, but that is normal behavior for a Bortle 2 sky at 300s and gain 100: you are close to the read-noise-limited regime, which argues against shortening the exposures.

The setup matches the target. At 835 mm and 0.93"/px on a 6248x4176 sensor, the 1.61° field frames the SH2-114 region well; the nebula extends well beyond it but the targeted portion is correctly placed. Sampling is slightly fine for typical seeing: with a measured FWHM around 5 px at center you are in practice limited by seeing and drift rather than by the optics, and 2x binning at integration would gain signal to noise with no real loss of detail. Gain 100 (unity) and offset 50 are healthy, with no measured dark clipping. One point to watch: sensor temperature at 0°C, cooling to -10°C would noticeably cut dark current on 300s subs.