A Keplerian telescope in air has an objective of focal length and diameter
PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Geometrical optics and imaging · Geometrical optics and imaging
What an Instrument Can See, Ch Pupils: the aperture of a linear system
Problem
A Keplerian telescope in air has an objective of focal length 200mm and diameter 50mm, and an eyepiece of focal length 25mm and diameter 20mm placed 225mm behind it, so the two share a focal plane. A circular diaphragm 10mm across sits in that common focal plane. The telescope looks at distant stars.
((a)) Trace the cone from an on-axis star through each of the three apertures in turn and identify the aperture stop.
((b)) Give the diameter and position of the entrance pupil and of the exit pupil.
((c)) Trace the chief ray, through the centre of the stop at angle θˉ, and find which aperture stops it first; that aperture is the field stop. Give the angular radius of the field in object space and in image space, the angles subtended by the entrance and exit windows.