Re: [ATM] Looking for information on a telescope design

["Clyde Bone" <clydebone@zipnet.us>]

Scott:

 

If the Mersenne design is constructed so that the front element of the imaging instrument is as close as possible to the secondary, the finder field is easily masked out.  I use a circle of black posterboard behind the secondary.  This is impossible with the Gregorian configuration due to the extra distance.

 

I welcome pros & cons discussions when they contribute to improvement.  The Mersenne has some problems, i.e. I cannot use an eyepiece longer than 26 mm focal length.  Longer eyepieces start to make a dark hole in the center of view. My favorite is a 20mm Nagler II.  Finding an object is difficult for me if the telescope is pointed very near the zenith using the Sky Commander because the mirror arrangement creates direction confusion.

 

If designed properly, the Mersenne has no aberrations to third order and the field is flat.

The problem that the imaging element has to handle wide angles projected from the secondary mirror is easy to solve-it does not exist.

 

I do not know where " This means that the imaging element in the Mersenne arrangement will have four times more coma and sixteen times more astigmatism than it would have if used alone" comes from, but it is totally in error.  There is no coma or astigmatism to the edge of the power field.

 

Clyde  
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