Astrophotography diagnosis of LDN43: Backfocus error and tracking drift

Clearly unfavorable conditions for this target. LDN 43 is a dark nebula: its whole appeal rests on the contrast between dust and the stellar background, hence on sky background level. You are under Bortle 8 with a 63.7% gibbous Moon 35.1 degrees above the horizon and, worse, only 11.4 degrees from the target. That is the worst case: the lunar halo lands straight on the field and crushes the very contrast you are after. No filter saves this, an absorption nebula works in broadband. The measured background margin (e_margin 2.6) confirms an already raised background. The right call is to move this target to a Moon-free slot, late in a waning lunation or at new Moon.

The setup is mechanically coherent but poorly matched to LDN 43. At 994 mm and 0.78 arcsec/px you are oversampled relative to typical seeing: the 2.63 px central FWHM works out to about 2 arcsec, so you pay in signal per pixel what you do not gain in resolution. A 1.35 degree field is also very tight for an extended dust region like this one; a shorter focal length, or software 2x2 binning, would give better return. On settings, gain 100 (unity) and offset 50 are healthy, with no dark clipping and no saturation. The sensor temperature at 0 C is high for an ASI2600MC Pro though: go down to -10 C to cut dark current and keep the dark library reliable.