It is a rule that is used to photograph night sky and to avoid Star trails. It is more complicated to calculate than 500 Rule so it is better to use [PhotoPills] for that.
Factors
There are several factors at play that help you to setup your ideal exposure
- Aperture
- Photosite size
- Focal length
- Star declination
How to use it with PhotoPills
- Go to PhotoPills app and go to SpotStars menu
- Set your camera model
- input focal length and aperture
- Set minimum declination (0 degrees for worst-case scenario if you don’t know what i)