Re: [ATM] Baffling a Gregorian and corrector plate fabrication.

[Kevin MIchael Zabbo <chaosopher23@yahoo.com>]

The baffle on a Greg is one problem, mainly because
there are two of them.  One is around the secondary
and the other is for the eyepiece.  The one around the
eyepiece can be made smaller with a Coude arrangement
of mirrors, which puts the EP at an upside-down Newt
position.  This makes things easier to reach, mostly,
especially if you're going to put this Magnificent
Monster on an EQ platform of some kind.  (You are
going to put this on an EQ platform with a nice drive,
right?)  You won't have to drill a hole in the primary
with the Coude arrangement, either, and the best part
of the Coude is that you are not looking at the sky
directly.  The baffle will block enough light to make
things enjoyable.

I don't have any software for baffling.  Instead, I
draw a full-size plan and draw the light rays parallel
coming in, and the field rays at + and - angles from
the edge of the primary.  Then I draw the baffle in
place and measure that drawn-in baffle to get the
close-enough measurements.  A boat designer showed me
this method.  It's called lofting.

Kevin of Eastern Iowa
Seeker of the Darkness

ps. Law of Precision: Measure with a micrometer, mark
with chalk, cut with axe.

--- Douglas S Angle <Douglas.S.Angle@can.dupont.com>
wrote:

> I'm contemplating building a Gregorian, and I've
> been looking at different 
> design considerations.  I've browsed through the
> archives, read Rutten & 
> van Venrooij on the subject.  One thing I can't
> figure out is how to 
> baffle such that stray light can't get from the
> entrance aperture to the 
> eyepiece.  There's an article in ATM about a
> newt-cass-gregorian 
> telescope, but the article doesn't address baffling
> at all, and the 
> pictures don't look like there's any attempt to
> baffle.  I did a full size 
> drawing, and I can't see how to catch more than
> about 1/2 the stray light. 
>  For reference, my design was:
> primary diameter 16"
> primary focal length  64   f/4
> secondary  diameter 4"
> distance of focus behind primary 15"
> 
> I would be interested in hearing from anyone who has
> built a gregorian, or 
> advice on how to solve the baffling problem. 
> 
> I also considered a shorter focal length primary
> combined with a corrector 
> plate.  I understand the principle of the Schmidt
> camera, where the 
> corrector is placed at the center of curvature, and
> can be made using the 
> vacuum pan method.  If I were to move the corrector
> plate towards the 
> primary, is it true that the I can't use the vacuum
> pan method anymore, 
> because the shape is now different?  For that
> matter, is there any 
> difference between a corrector plate as used in a
> schmidt camera, vs one 
> used in a compound telescope so that the primary can
> be left spherical?
> 
> Thanks all.
> -Doug
> 
> This communication is for use by the intended
> recipient and contains
> information that may be Privileged, confidential or
> copyrighted under
> applicable law. If you are not the intended
> recipient, you are hereby
> formally notified that any use, copying or
> distribution of this e-mail,
> in whole or in part, is strictly prohibited. Please
> notify the sender by
> return e-mail and delete this e-mail from your
> system. Unless explicitly
> and conspicuously designated as "E-Contract
> Intended", this e-mail does
> not constitute a contract offer, a contract
> amendment, or an acceptance
> of a contract offer. This e-mail does not constitute
> a consent to the
> use of sender's contact information for direct
> marketing purposes or for
> transfers of data to third parties.
> 
> Francais Deutsch Italiano  Espanol  Portugues 
> Japanese  Chinese  Korean
> 
>           
> http://www.DuPont.com/corp/email_disclaimer.html
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 


I published my first novel!  You can get it here, from the publisher!  
http://www.publishamerica.com/greetingcardpro/pickup.asp?CardSentID=126045&rID=48283



Their search stringbox is on the right side about halfway down.

search using my name:  kevin michael zabbo
and it will take you right to my book page.

The title is anna's blood, which also takes you there.

Please order your copy soon!  I love you!

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com 
_______________________________________________
ATM mailing list http://www.atmlist.net/