ABSTRACT

The combination of telescope and camera should give the object the right emphasis within the frame. There are simple calculations that give the field of view in arc minutes. A number of terms loosely describe brightness in many texts, namely, luminosity, flux and magnitude. Luminosity relates to the total light energy output from a star; flux is a surface intensity like an incident light reading in photography, falls off with distance. Photographers are aware that the intensity of a light source reduces with distance, for instance the light intensity from an fl ashgun obeys the inverse-square law. The needs of the visual observer and astrophotographer are different too since the human eye has a higher resolution than a conventional sensor. Post-exposure image manipulation cannot restore lost image resolution, but image sharpness can be increased later on using photo software. Image sharpness has no agreed measure but is people perception of contrast between adjacent light and transition area.