Improving Focus (part 1)
Longer exposures and higher magnifications demand better focus.
In the beginning, focusing a camera required good eyesight, a ground glass screen with a fine finish and patience. In time, ground glass had various optical aids added, including split field and microprisms. It still required patience. With the invention of autofocus, SLR and DSLR viewfinder screens were only required to show the composition and started shrinking, camera lens designs changed their architecture to permit increasingly rapid response times and the whole concept of hyperfocal distance and depth of field was largely forgotten by the masses.
In astrophotography, precise focus is essential; all puns aside, stellar images ruthlessly expose poor ...
