Subframe

An integration log. What was shot, what was thrown away, and how long each target really took once the discarded frames are counted honestly.

NGC 7000

North America Nebula · Cygnus

Target 25 h total, narrowband, 300 s subframes. Currently 58% of the way there.

Ha 7h 10m

OIII 4h 45m

SII 2h 30m

Integrated 14 h 25 m across 11 nights 173 subs kept · 41 discarded

Integration log

Night	Filter	Subs	Exposure	Kept	Guide RMS
2026-09-19	Ha	24	300 s	22	0.61″
2026-09-18	OIII	21	300 s	19	0.68″
2026-09-14	SII	18	300 s	12 · wind	1.42″
2026-09-12	Ha	30	300 s	30	0.54″
2026-09-11	OIII	26	300 s	18 · cloud	0.72″
2026-09-06	Ha	28	300 s	27	0.59″

Discards are listed with a reason. Frames get cut on eccentricity above 0.55 or on a visible gradient, and the count stays in the log either way — an integration time that quietly hides its rejects is not a measurement.

Rig

Optics: 80 mm f/6 apo480 mm with the flattener
Camera: Cooled mono CMOS−10 °C, gain 100, 3.76 µm
Mount: Belt-modified EQ5guided, no permanent pier
Guiding: 30 mm scope, 2 stypical 0.6″ total RMS
Filters: Ha / OIII / SII3 nm, 31 mm unmounted
Sky: Bortle 6which is why it is narrowband

Processing

Calibration with darks and flats matched to the session, no bias — the dark library is rebuilt twice a year rather than reused indefinitely. Stacking with drizzle off; at this sampling it adds nothing but file size.

Stretching is done in two stages with the mask built from the Ha channel, which keeps the faint outer structure from flattening out when the bright rim is brought down. Colour mapping is the usual Hubble palette, adjusted until the greens are gone.