Aberrator    News  Development    Star-Test    FAQ    Examples    Download    Links

DEFOCUS
Although all scopes have this aberration, this is the only one you really need. Without it you cannot focus correctly.

Picture
Picture

On the left a perfect telescope in focus, on the right a 30% obstructed telescope.  The obstructed telescope has a brighter 1st diffraction ring.

Picture Picture

The same telescopes now 1 wave defocused (+/-). Notice that the center in both of the scopes is now dark (no airy-disc).

Picture Picture

The telescopes now at 2.5 wave defocused (+/-). Now the light/dark patterns are differening a lot more. The overal pattern is alike but the distribution of the light over the rings is different, again the obstructed telescope shows more light in the rings. The wavy nature of the rings is due to the calculation-methods (slight undersampling). The Aberrator will show more of these effects when defocus is more then 10 wavelengths. For such defocus values a higher aperture will lead to more realistic calculations.

[ Aberrator] [  News] [Development] [  Star-Test] [  FAQ] [  Examples] [  Download] [  Links]