Re: [ATM] 40" mirror

[DHA352@aol.com]

Matt,
    Is there any way in a Nasmyth focus for the  secondary to be 
significantly less than one-half the diameter of the  primary?  I always envision the 
eyepiece of a Nasmyth at the COB.   This buts the focus of the secondary near the 
primary, thus requiring a 20"  secondary for a 40" primary.  Or do I have the 
design of a Nasmyth fouled  up?  
 
Clear skies
Don
 
 
In a message dated 12/26/2004 8:26:12 A.M. Eastern Standard Time,  
mariusrf@bellsouth.net writes:

Hi  Jerry,

It's a trade off as most engineering decisions. If you make a  folded
newtonian the scope will be shorter and the mechanical problems with  the
long truss poles will be reduced. A shorter scope can hold its shape  better
with less sag. It has less windage and if you use a Nasmyth focus  it's much
easier to use than climbing a ladder . The drawback is one extra  mirror but
you could buy that since it's a small flat , and the collimation  procedure
would have one or more extra steps .

best regards,
matt  tudor


-----Original Message-----
From: Jerry B. Hillman  <JBHillman@ev1.net>
To: matt <mariusrf@bellsouth.net>
Cc:  'The Amateur Telescope Makers List' <atm@atmlist.net>
Date: Sunday,  December 26, 2004 7:34 AM
Subject: Re: [ATM] 40" mirror


>Hi  Matt,
>I am looking into Cas, coude, etc. designs, but haven't learned  enough
about
>them to make a decision to go that route. This is only  my third mirror.
>Succeeding on the simplest terms, ie. a Dob/Newt is  probably going to be a
>challenge as it is without trying the exotic  designs.
>
>Clear  skies,
>Jerry
>
>

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