[ATM] Who invented that telescope?

[artbianconi at blast.net]

To all of you who responded so generously. . . . . Thanks

Dave Groski said that you can build one of these with a primary 
aperture of up to six inches without the need to add a corrector 
lens.

If I am going to build it, I want the fastest mirror I can install 
without adding a corrector. I am not capable of interpolating 3' to 
4.25" optics to 6". Maybe Dave will respond with numbers for the 6.

Bill's telescope had exceptional contrast and, as expected, with a 
F/L of 111 inches (!) his  conventional eyepieces gave really large 
magnifications without  challenging the quality of the optics. And, 
the eye-relief was enormous!

Here are some specs I found with Michael Lindner's help. Perhaps one 
of you with optical-math skills can tell me what these number would 
be if I built the scope with a 6"mirror. 

Thanks

Art




Measurements for 4.25" Kutter Schiefspiegler  

Primary mirror aperture 4.25" 
Secondary mirror aperture 2.20" 
Radius of curvature 127.5" 
Effective focal length 111.0" 
Mirror separation 36.0" 
Secondary/focus separation 46.45" 
Primary tilt 2.76 degrees 
Secondary tilt 6.41 degrees 

Measurements for 3" Kutter Schiefspiegler  

Primary mirror aperture 3.00" 
Secondary mirror aperture 1.44" 
Radius of curvature 81.5" 
Effective focal length 71.0" 
Mirror separation 23.13" 
Secondary/focus separation 29.00" 
Primary tilt 2.9 degrees 
Secondary tilt 6.78 degrees 

However, the ray tracing capability of my 3D solids modeler is 
exceptional and with any luck, it will tell me what changes I need to 
make when locating the glass.

Hopefully Dave will respond 




This past weekend, I attended the Mirror Making Event hosted by the
Delmarva Stargazers and held at the Mallard Lodge in Smyrna, 
Delaware.

Two of those who supported the participants were Dave Groski and Bill
Cheng.

Bill brought a rather unique, all wood telescope with him which has 
an
exceptionally long focal length and an off-axis convex secondary.
These combine to "fold" the sight axis so the finished design is
relatively short in spite of it's very long focal length.

I can best characterize the design as something that might result if
someone dropped a Cassagrain from a second story window onto a fence
post! At first glance, nothing seems to line up!

Bill built the telescope using data compiled and enhanced by Dave of
an earlier design by someone else.

I'd like to research this some more but can't find the name of the
original designer whose name was hyphenated and which I think started
with "Shief" or some similar sounding name. 

Can anyone fill in the blanks for me?

Thanks

Art Bianconi

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