ImageReasonAstrophotography and Night Capture
How big will the Moon be in my frame, and what should I test?
Enter your focal length, sensor, and a reference exposure to get a lunar framing estimate and a disciplined test bracket.
Answer
Want to learn more? Astrophotography Exposure, Star Motion, Tracking, and Stacking
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Calculate to see the framed lunar disk.
| Focal length | Frame share |
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Calculate a result to generate a copyable plan.
Framing is FOV; exposure is a test-frame question
The Moon's size in your frame is a field-of-view question. Its exposure is a test-frame question. A longer focal length makes the lunar disk occupy more of the sensor, but atmospheric conditions, phase, haze, vibration, and the desired balance with a foreground still determine the capture. This planner gives a geometric framing estimate and a disciplined bracket from a reference you control.
A 400mm lens on a 36mm-wide sensor covers about 5.15 degrees horizontally. With a typical .52-degree apparent lunar diameter, the disk is about 10 percent of the frame width. Doubling to 800mm makes it near 20 percent, while also demanding more stability. For an isolated full or partial Moon, begin from the exposure you have actually tested, bracket around it, and inspect bright lunar texture at full review size. Do not carry that sequence into an eclipse without separate planning.
This is a planning calculation, not a certification. Confirm the relevant camera, lens, card, printer, contract, location, or workflow constraint in the real setup before relying on the result.
Make one controlled test with the important variable held constant. Inspect the subject detail, motion, highlights, and intended output, then adjust the setting that protects the priority you named.
FAQ
- Why not give one "Moon exposure" setting?
- Lunar brightness and the scene vary. A setting that works for one phase, atmosphere, lens, or foreground can be wrong for another. This tool creates a transparent test plan instead.
- Is this a guarantee?
- No. The result is bounded by the inputs and assumptions shown on the page. It is designed to support a better next decision, not replace a test, measurement, proof, or professional judgement where one is needed.