By Alexander Merz · Updated on · Details checked on 6 October 2026
Astrophotography calculators
How to use these calculators
- The calculators are pre-filled with example data: a Newton with 200 mm aperture and 1000 mm focal length at f/5.
- Select the numbers already in the fields, delete them and enter your own.
- Do not use thousands separators for large numbers.
- Canon APS-C sensors measure 22.3 mm x 14.9 mm.
- Nikon APS-C sensors measure 23.5 mm x 15.6 mm.
- Full-frame sensors measure 36 mm x 24 mm.
This application has been designed specifically for astrophotography enthusiasts and offers a user-friendly platform for performing a range of important calculations required to create stunning astrophotos. The features are divided into several sections to ensure greater clarity and ease of use.
- Field of view – Calculates the visible field of view of a telescope in degrees, based on the telescope’s focal length and the size of the image sensor in millimetres.
- Focal ratio – Calculates the focal ratio of a telescope, based on its focal length and aperture in millimetres.
- Image scale per pixel – Calculates the image scale of a telescope in arcseconds per pixel, based on its focal length and the pixel size of the sensor in micrometres.
- Focal length and focal ratio required for critical sampling – Calculates the focal length and focal ratio required for critical sampling of a sensor, based on the telescope’s aperture in millimetres, the pixel size of the sensor in micrometres and the sampling factor.
- Focal length required for a desired image sampling – Calculates the focal length a telescope needs in order to achieve a specific image sampling in arcseconds per pixel, based on the desired sampling and the pixel size of the sensor in micrometres.
📷 From calculating to photographing
Celestron Omni 2x Barlow Lens 1.25″ ($41.95€ 52) – extends the focal length for planetary sampling – matches the values from the calculator
Check availability* →Check availability* →
Apertura 1.25″ Moon FilterOmegon Premium Moon Filter 1.25″ ($14.95€ 19.90) – for high-contrast Moon shots with any camera
Check availability* →Check availability* →
You’ll find the right camera for your sampling in our guide Astrophotography cameras – or you can skip the maths entirely with a smart telescope.
The application is designed to be useful for both beginners and experienced astrophotographers. The easy-to-understand instructions and simple operation allow users to make the most of their equipment and create impressive astrophotos of galaxies, star clusters and nebulae.
The results of the calculations help to deepen the understanding of the technical aspects of astrophotography and to continuously refine photography techniques.
The calculator shows what your setup can do – the quick check helps if the telescope is still missing.
Six short questions, an honest answer by email – even when binoculars are the better choice.