From: "Dwight K. Elvey" 
To: atm{at}shore.net
Reply-To: "Dwight K. Elvey" 


Hi
 The best way to describe what is needed is to
place your eye ball where a stray light source might be. If you can see the
field lens of the eyepiece, that is a path you need to block. The only way
you should be able to see the field lens is by the normal optical path.
 It is the combination of the field stop, eye piece barrel and
focuser tube in relationship to the field lens that would determine the baffling.
 While it may be true that just seeing the field lens may
not make it through the eyepiece as a direct path, it will surely reflect
from one of the internal surfaces and cause problems. From a technical
sense, if the light cone is greater than the f-ratio of the lenses in the
eyepiece, it shouldn't be an issue. From a practical standpoint, any stray
light that makes it to the field lens should be blocked.
 Plot everything out and then lay a straight edge along
different paths. If you can lay it in such a way that it clears the other
normal obstructions and makes it to the field lens, that is what needs to
be blocked.
 It is the field lens that really counts. If you block
all the light to the field stop, it may be over kill. Still, you need to
consider reflections.
 I hope this makes a little more sense?
Dwight

>From: "Mike and Sara" 
>
>
>Hello!  A couple of rudimentary questions, so bear with me.  Given the FOV
>for my two inch eyepieces, I presume I start the rays from the field stop of
>the EP?  Alos, do I start the rays from a point, or a line segment (which
>would simulate a focal plane, I presume).  If a line segment, how long
>should the line segment be?  Thanks and best regards.
>
>Mike Heald
>
>
>  ----- Original Message -----
>From: "Bob May" 
>To: "atmlist" 
>Sent: Monday, January 06, 2003 6:31 AM
>Subject: Re: ATM Focuser Baffle and Dall Kirkham design with Naismyth Focus
>
>
>>
>> Draw out on a large piece of paper the design of the scope and setup the
>EP
>> FOV on the axis as if the tertiary wasn't there - this makes drawing lines
>> easier.  When you start drawing the lines, draw a set of on-axis lines, a
>> set of off-axis lines to at least the secondary and hopefully to the
>primary
>> (half degree angles do get to be a bit weary to draw and the obstruction
>> between the primary and secondary will be minimal anyway) and use that
>> drawing to size the baffles on the secondary and tertiary and the size of
>> the tertiary mirror for best results.  You also want to use the
full 2" of
>> the EP as the FOV to insure the best results with the baffles although you
>> may also desire to drop that down to about 1.6" which is
about the largest
>> that you really get in a FOV on a 2" EP.
>> Bob May
>> http://nav.to/bobmay
>> bobmay{at}nethere.com
>> NEW! http://bobmay.astronomy.net
>>
>>
>>
>
>
>

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