ImageReasonAstrophotography and Night Capture
How many frames does my star-trail plan need?
Enter your per-frame exposure, interval gap, and target session length to see frame count, total captured light, and how much time the gaps actually consume.
Answer
Visualize
Calculate to see the frame/gap timeline.
| Quantity | Value |
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Compare
| Gap | Frames | Coverage |
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Plan
Calculate a result to generate a copyable plan.
A sequence-planning problem, not just an exposure
Stacked star trails are a sequence-planning problem as much as an exposure problem. A planned session has at least three clocks: the exposure time of each light frame, the gap between frames, and the total time the camera remains in position. The camera may gather a great deal less light than the elapsed time suggests when a small interval repeats through a long session.
Enter the per-frame exposure, the interval gap you intend to program, and the session duration you want. The planner calculates how many frames are needed, total time spent exposing, total time spent between frames, and the actual duration after whole frames are counted. It does not decide the exposure for your sky, because light pollution, moonlight, lens aperture, ISO, sensor behavior, and composition are all outside a simple schedule calculation.
For example, a two-hour session using 30-second frames with two-second gaps needs 225 light frames. The camera gathers 112.5 minutes of light across about 120 minutes of elapsed time, leaving about 7.47 minutes between frames. That may be a workable planning point, but it does not guarantee that a stack will have seamless trails. Write time, long-exposure noise reduction, intervalometer behavior, and changed conditions can introduce delays the arithmetic does not know.
Use the output to prepare the session: choose an intervalometer, confirm enough card and battery capacity, lock framing and focus, make test frames, and inspect early captures for unwanted light, condensation, or gaps. Keep the setup stable. A sequence may be difficult to align if the camera moves. If you plan dark frames, the page shows their added time separately so they are not confused with trail light frames.
This tool intentionally avoids celestial navigation, weather, and safety advice. Check local conditions, property rules, footing, weather, and personal safety independently. The planner is only a transparent way to turn a chosen capture recipe into a repeatable sequence.
FAQ
- Does a zero-second gap guarantee continuous trails?
- No. The arithmetic has no planned gap, but cameras may still pause for writing or processing.
- Should I use one very long exposure or a stack?
- This planner schedules a stack. The choice depends on conditions, camera behavior, processing, and the recovery options you want.
- Can this tell me the right ISO or aperture?
- No. Make test frames in the actual sky and decide those settings separately.