when is an astronomical telescope is said to be in normal adjustment. and how it works under this condition.?

Answer 1

Hi. All telescopes must be collimated. This is like adjusting your rear view mirror in a car. Different scopes need different adjustments. A reflector has to have the main (rear) mirror set to line up with the secondary, and the secondary must align with the lens. A refractor is normally not adjustable. When set up properly the image has little coma or chromatic aberration and the image is at its best.