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Old 08-09-2008, 04:38 PM
Dennis
Dazzled by the Cosmos.

Dennis is offline
 
Join Date: May 2005
Location: Brisbane
Posts: 11,823
Just some reminders. If anyone is going to the expense of having one of these made by an external supplier, don’t forget to read the CN post – it continues to grow with new information. The formula I used was as follows, for long focal length ‘scopes:

(Bar width + inter-Bar gap) = Focal length/(Range 150-200).

The range 150-200 is a variable denominator to allow for a calculated result that is a “sensible” value such as 12mm, 6mm, etc rather than say, 10.1732mm. I’m not sure how scalable the design is; my bars and inter-bar gaps are 6mm with the main central bar being 15mm wide.

For short focal length ‘scopes (less than 800mm?) the formula becomes:
(Bar width + inter-Bar gap) = (3)x(Focal length)/(Range 150-200).
This x3 multiplication factor prevents the bars becoming too thin.

Don't forget to post your pics!

Cheers

Dennis

Last edited by Dennis; 09-09-2008 at 01:19 PM.
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