From: Goran Hosinsky 
To: atm{at}shore.net
Reply-To: Goran Hosinsky 


Hello,
I would like comments on the following idea for a planetary scope. The
goals are: long focal length well baffled Newton, minimum secondary
obstruction and comfortable viewing position. I think the goals can be
reached with this solution but I might be missing something fundamental.

-250 mm f/12 primary mirror, placed about 300 mm above ground.
-Secondary 100 mm before focus at 3200 mm above ground
-Tertiary mirror 230 mm from optical axis throwing the light
   down parallel with the optical axis
-50 mm acromat fl=380  600 mm from primary mirror focus This
   will give an image 1050 mm further down from the lens with
   3x amplification giving a f/36 system
-flat mirror shortly before focus angling the light normal out
   from the tube for the eyepiece mounting at about 1550 mm above
   ground

The above introduces 2 extra plane mirrors and one objective. The plane
mirrors are near focus and should not be too bad for the image.

Variations of this might be

- use a singlet lens and color filter when observing
- use two identical photographic objectives front - to - front.
  The first with focus in primary focus giving parallel light
  out, the second focusing this parallel light at a convenient
  distance.

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