Astrophotography diagnosis of IC 1848: Tracking drift

Very favorable conditions. The Bortle 2 sky is a major asset: the background stays dark with no marked light-pollution gradient, confirmed by the background map where the plane amplitude is only 7% with an R² of 0.14 (so no real oriented gradient). The Moon, 68% waning gibbous but below the horizon and 144° from the target, contributes nothing: lunar pollution ruled out outright. On an emission nebula like IC 1848, this context allows long subs with no compromise, and the low background-to-black-point margin (e_margin 1.85) is normal behavior for a narrowband filter under such a dark sky, not a sign of underexposure.

A coherent setup for this target. At 190mm focal length, the 3.36° field comfortably frames IC 1848 with margin at the edges, a good fit for the Soul Nebula. The 3.15"/px image scale is strictly undersampled, but that is a deliberate choice on a wide nebular field: the measured FWHM of 1.3-1.8 px confirms stars sit right at the sampling limit. For diffuse Ha nebulosity this is not a penalty. On settings, gain 200 on the ASI585MM remains reasonable with 0% saturated pixels, offset 15 produces no dark clipping, and the sensor at -20°C is properly cooled. Nothing to change there.