Astrophotography Calculators

Use our free online calculators to work out your best exposure times and other indicators for your gear.

Calculators & Tools

NPF Rule Calculator

NPF Rule Calculator

Work out your best exposure time for sharp stars with our free calculator

500 Rule Calculator

500 Rule Calculator

Use our free calculator for the 500 Rule for exposure time

Focal Ratio Formula and Calculator

Focal Ratio Formula and Calculator

Use our free focal ratio calculator to work out how fast your telescope is

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