Folded Newtonian Optical Layout
The 6" flat obstructs 37% of the diameter and 14% of the area of the primary
2" diagonal - only optical component that was purchased

The problem with spherical mirrors

• Spherical Mirror
  Diameter = 16" (400 mm)
  Focal Length = 10' (120", 3000mm)
  f/7.5
  Thickness = 1.5"

• Assume Entrance Pupil = 400mm
  Minimum magnification = 7 mm exit pupil
  57x
  Requires eyepiece = 53mm fl ~ 1degree FOV of sky

• Maximum magnification
  2mm exit Pupil
  200x
  Requires eyepiece = 20mm fl ~ one quarter degree of sky

• Eyepiece Built: 2" diameter
  44mm Focal length - super Plossl design
  Gives 70x mag and 5.7mm exit pupil
  field of view = span of the double cluster

Primary is spherical? What about aberration and coma?

What to do:

1. Ignore it?

2. Refigure to a parabola? Maybe not.

3. Correct optically? Use thick positive lens at image plane (Simple PVC)

4. Deform the mirror to form a sphere into a parabola (pull down center)

We tried # 4 first!

The flexing mirror cell