Astrophoto Tracking Exposure Time Min

Total Integration Time in Tracked Astrophotography

Deep-sky astrophotography almost never relies on a single long shot. You capture a stack of shorter exposures instead, called subs (sub-exposures), and combine them afterward. To get the total integration time in minutes, you compute total = (number of subs × exposure per sub) ÷ 60. Take 60 subs of 120 s each, and you end up with (60 × 120) ÷ 60 = 120 minutes of total signal.

How long each sub can run comes down to how well your mount tracks. Without autoguiding, even a solid equatorial mount might keep stars round for only 60–120 s before periodic error and polar-alignment drift start smearing them into streaks. Add guiding and you can push subs to 300 s or beyond. From there you decide how many subs it takes to reach the integration time your target needs. Faint nebulae are demanding, often calling for several hours.

Applications

It helps when you're planning an imaging session. Pick a per-sub exposure your mount can handle cleanly, see how many frames fit into the sky time you've got, and check whether that total is actually enough for the object you're after.

FAQ

Why not just take one very long exposure? A single long shot blows out bright stars, gets wrecked by a passing satellite or a gust of wind, and turns any tracking error into trailing across the whole frame. A pile of shorter subs is far more forgiving, and stacking them averages the noise away.

What limits my sub length? Mostly your tracking and guiding accuracy, but sky brightness matters too. Under light-polluted skies you're forced into shorter subs so the background doesn't wash out.

How much total integration do I need? Bright targets can come together in 30–60 minutes. Faint galaxies and nebulae are another story, and usually reward you for several hours or more.