Rule 600 (Spot Stars)

Formula to calculate maximum exposure time to capture Stars as Spots that take into account Sensor Size, Focal Length and Minimum Star Declination. You can estimate the Minimum Star Declination using PhotoPills Night AR or PhotoPills Planner Night AR.

Rule 500 (Spot Stars)

Fast way to estimate the maximum exposure time to obtain stars as spots. It's value is obtained by dividing 500 by the focal length.