Field of View is a simple web application to aid in astrophotographic planning and composition. It allows you to determine how large a deep sky object might appear based on the sensor-size of the capture device (with common 35mm/DSLR/consumer camera sensor sizes as well as custom sizes) and the focal length of the lens or telescope, with the option to include the modification factor of a focal reducer.

Images of the objects are retrieved from NASA's SkyView.

It is hosted on observationapp.com.

M31, framed for a 600mm telescope and an APS-C sensor:

BSD. See LICENSE file.