Improving Focus (part 2)
Using a computer to automatically determine the best focus position improves image quality over extended periods and enables unattended operation too.
We take focus for granted on modern consumer cameras. Their powerful algorithms evaluate the image in real time and not only focus at a point but are able to track a subject and even predict the focus position of a moving object. In astrophotography, although we are working at infinity, it is by no means a fix-and-forget process. The extended imaging time during the night requires repeated monitoring and focus correction; in most cases, carried out in-between exposures. These corrections are necessary to compensate for several complications:
- thermal expansion or contraction ...
