Re: [ATM] Baffles

["Nils Olof Carlin" <nilsolof.carlin@telia.com>]

John,

> I have taken the liberty of adding a few lines to your drawing Anthony:
> 6f8T8MODJ.jpg

It could be found at:
http://www.atmlist.net/contrib/johncdeitz-at-comcast-dot-net/6f8T8MODJ.JPG


> in illustration of baffle method by drawing.

Judging from your drawing, you shade the lowest (nearest primary) part of 
the tube by baffling. I claim that this part cannot be illuminated by 
reflection via the primary and thus contribute a strong grazing reflection.

It can, of course, be illuminated directly through the tube opening, and be 
potentially visible via the secondary by "back-scatter", but so is the 
baffle! - and baffling for this purpose is thus meaningless. With a 
refractor, it can be meaningful since what you see from the eyepiece is the 
shadow side of the baffle, not the illuminated side as in a Newtonian.

Your method is appropriate for a refractor.  As I recall vaguely, Astronomy 
magazine advocates the same principle for a Newtonian, and so did Rich 
Coombs on a webpage that I haven't been able to locate with Google.

However, I claim (and I understand Anthony agrees here) that this is not 
appropriate for a reflector.

regards,

Nils Olof


One proceeds by 1) sketch a line from edge of tube to edge of mirror nearest 
2)another line from "far" limit of field 3) the intersection of these two 
lines is baffle nearest primary. This results in more baffles and the first 
(nearest primary) being considerable closer than in original sketch. See Pg 
222 Telescope Optics, 1988.
> John Deitz


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