Decide how much total integration you want, then see how many sub-exposures it takes, how many clear nights you'll need, and how much disk space — so you can plan a deep-sky campaign realistically.
Modern deep-sky images are stacks of many sub-exposures totalling hours of integration time. Faint targets reward more data — signal-to-noise improves with the square root of total integration — so knowing how many subs and nights a goal takes helps you decide whether a target is realistic from your site.
Longer subs cut overhead and read noise but risk losing frames to clouds, satellites or guiding glitches, and can saturate bright stars. The sweet spot is "sky-limited" — long enough that sky background swamps read noise. Our field-of-view and guiding tools help you get the gear side right first.
It depends on the target and sky. Bright objects look good in 1–3 hours; faint nebulae and galaxies often want 10–30+ hours, and narrowband from light-polluted skies can run higher still. Because SNR grows with the square root of time, doubling your data only improves noise by ~1.4×.
The stretch of real darkness when your target is high enough to image well (typically above ~30°). It shrinks for low-declination targets, near twilight, and around the full Moon. Be conservative — clouds rarely cooperate for a full night.
Every sub costs download time plus dither-and-settle. With 300 s subs and 20 s overhead you lose ~6%; with 30 s subs and the same overhead you lose ~40% of the night. Longer subs (when guiding allows) reclaim that time.
Longer subs, less aggressive dithering, a faster (lower f-ratio) system, or simply a lower integration target. A dual-rig or wider sensor also gathers more sky per frame.
A planning estimate. Real yield depends on weather, target altitude, the Moon and how strict your frame culling is.