Go Observing Help

Choosing the right exposure time

Increasing the exposure time of an observation usually makes it look better - less noisy and "grainy". However, there can be good reasons for choosing a shorter exposure time:

  • If there is something quite bright in the image, a long exposure time might make it "saturate" which will spoil the image (and can even temporarily damage the camera).
  • Obviously, longer exposures take longer to carry out. Therefore it might be slightly more difficult for the computers at the telescope to find enough time to take your observation, so it might be delayed.
  • Taking exposures that are longer than needed is wasteful. For this reason, astronomers are very careful to choose exactly the right exposure time for their observations - not more, not less!