RE: [ATM] Alan Scott's Deep Space telescope

["Alan Scott" <alanne1956@hotmail.com>]

Mark,
  Thanks for the Protostar recommendation.  This looks like what I have been 
looking for.  WalMart black felt isn't quite cutting it.

  I have tried a ring baffle.  The problem that I have is that I am starting 
to use a "Big Barlow" by TeleVue, and it extends completely through my 
focuser, and knocks the ring baffle off of the end of the focuser.  
Unfortunately, no - I DON'T remember to remove it before using the barlow.  
So, this is still in work.
  Filter slides are tough for this scope.  The focuser, as currently placed, 
extends INTO the center of the secondary cage by quite a bit (when the 
eyepiece is racked in all of the way).  In fact, it goes to just short of 
the lightcone coming straight into the 12" mirror, or 1/2" inside the 13.5" 
inner ring.  So, no room for a filter slide.  I did this to stay as close to 
the secondary as possible, thus allowing a fairly small secondary.  Under 
normal use, the focuser stays outside of the ring, however.


Not a bad idea!!  I will have to stew on it.  Two issues come to mind.  1) I 
currently have almost NO defraction spikes from the current setup, with the 
3 legs to the thin spider wires.  I really don't want to loose that.  2) I 
don't think that this would solve my issues any more than putting a baffle 
on the outside ring, on the opposite side of the focuser.  I would still get 
light polution falling on this baffle, and if it isn't totally, absolutely 
flat black, it would pass background glow into the eyepiece.

alan
http://www.xmission.com/~alanne/Astronomy.html


>From: Mark Holm <mdholm@telerama.com>
>To: atm@atmlist.net
>Subject: RE: [ATM] Alan Scott's Deep Space telescope
>Date: Fri, 08 Apr 2005 08:43:36 -0400
>
>Protostar sells some flocked paper that is specially chosen for telescope 
>baffling.  They say it is non-shedding,  stands up to a reasonable amount 
>of handling, and isn't bothered by dew.  Protostar is a quality outfit.  I 
>doubt they would make an advertising claim that wasn't reasonably 
>warranted.  I haven't used this material, so I am only passing on their 
>advertising info.  They have a web site.  Google for them.
>
>Don't forget a ring baffle under your focuser.  It is the most effective 
>and most weight saving place to put one.  I think Mel Bartels web site 
>shows how and where to locate it.  You could build a filter slide under the 
>focuser and incorporate the ring baffle into that.
>
>The next most weight saving place to put one is just behind the diagonal.  
>A combo of a ring baffle under the focuser and a baffle behind the diagonal 
>is probably the lightest weight scheme.  The behind the fdiagonal location 
>does have disadvantages.  More diffraction in the light path.  More mass 
>and wind catching area suspended on the spider.
>
>--
>Mark Holm
>mdholm@telerama.com
>
>
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