Integration time explained
Integration time is the total exposure in your stack: the number of subs the app kept, multiplied by their length. A Seestar that has stacked 360 frames of 10 s has one hour of integration. It is the single number that decides how deep an image goes.
Why more time keeps helping, and why it helps less each time
Stacking averages the noise down. Signal adds up in proportion to time; random noise adds up in proportion to the square root of time. So the signal-to-noise ratio of the stack grows as √T: four times the integration doubles the SNR, and doubling it gives you 41% more. There is no point where more time stops helping. There is a point where the next hour is not worth the night.
| Integration | SNR relative to 10 min | Gain |
|---|---|---|
| 10 min | 1.00× | 0% more than 10 min |
| 20 min | 1.41× | 41% more than 10 min |
| 40 min | 2.00× | 100% more than 10 min |
| 80 min | 2.83× | 183% more than 10 min |
| 160 min | 4.00× | 300% more than 10 min |
| 320 min | 5.66× | 466% more than 10 min |
What the three quality levels mean
| Level | Per-pixel SNR | What it looks like |
|---|---|---|
| Quick look | 3 | Target obvious, still noisy |
| Solid | 6 | Clean enough to share |
| Showpiece | 12 | Smooth faint detail, print-worthy |
These are the levels the calculator reports. The SNR is per pixel, at the scope's native scale, on the object's typical surface brightness. Real images look better than their per-pixel SNR suggests once you downsample, bin or apply noise reduction, which is why "quick look" is usable at all.
The target sets the time, not the scope
The spread between targets is far larger than the spread between telescopes. Four popular objects with the same scope from the same suburban sky:
| Target | Type | Solid image, Bortle 6, Seestar S50 |
|---|---|---|
| Orion Nebula | Emission nebula | 12 min |
| Western Veil Nebula | Supernova remnant | 1 h 33 min |
| Andromeda Galaxy | Galaxy | 1 h 27 min |
| Pinwheel Galaxy | Galaxy | 4 h 37 min |
The difference is surface brightness: how much light each square arcsecond of the object sends. Bright nebulae are done in minutes; faint face-on galaxies need hours, and from town they need a dark night and patience.
Spreading a target over several nights
Nothing says an hour has to be one hour. The apps stack one session at a time, so to combine nights, save the raw subs (the FITS files every one of these scopes can keep) and stack them together in free software such as Siril. Some apps can also resume a target and add to an earlier stack; check yours. Either way the maths is the same: 3 × 40 min is 2 hours.
What the number does not include
- Frames the app rejected. Wind, satellites and poor tracking throw subs away; add 10 to 20% to the plan.
- The Moon. A first-quarter Moon adds roughly one Bortle class of skyglow; a full Moon two or three. Plan broadband targets for the dark half of the month.
- Altitude. Low targets sit in thicker air and brighter sky. The figures assume the object is reasonably high.
Run any target through the calculator for its own three figures, or read how long subs should be for the other half of the question.
More guides
- Which smart telescope should you buy?
- How long should my subs be?
- The Bortle scale for smart telescope owners
- EQ mode and field rotation on smart telescopes
- Dual-band filters on smart telescopes: when they help and when they hurt
- Filters explained: VIS, Astro, UV/IR-cut, dual-band, CLS and solar
Updated 2026-08-27. Corrections: about page.