Re: [ATM] New Scope Design

[John Lynch <john_lynch2007@yahoo.com>]

Jacob,

A few comments about your design.  I've been working
on a similar configuration (8" f/6.25) and yours looks
pretty reasonable.

1)  Rule of thumb from Texereau is that the 100%
illumination diameter should be 0.009 X focal length
so that you can observe the full Moon in the lowest
power eyepiece.  For you, that would be 0.45" and your
NEWT results show 0.3175.  If you switch from 2.45"
fully racked-in focuser to Crayford with 1.6" height,
this will give you 0.4832" and the 75% illumination
diameter of approximately 1.2388" (don't want to go
over ~1.35" for 8" f/6 according to Texereau). 
2) Just remember that with the lower profile focuser,
you have to be careful with the drawtube penetrating
the light cone, so you might have to adjust the
focuser extra travel and carefully analyze the
geometry of your design.
3) Are you sure the tube thickness is 0.375", or half
of that.  This seems a bit much.  Remember that
thickness is [OD-ID]/2.  So, 3/16" or 0.1875 seems
more reasonable like a Parks fiberglass tube, for
instance.

Good luck!

John Lynch

--- Jacob Lauser <23tauri@gmail.com> wrote:

> Hey, guys!
> 
> I'm finally starting to design my new scope.
> 
> Seeing as I'm still very busy with law school, I
> figured I'd keep the
> design simple and go with a classic Newt.
> 
> I was going to go with a 10" F/5, but after getting
> ahold of a nice
> carbon fiber tube on the cheap, I thought I'd switch
> to an 8" design.
> 
> Using NEWT, I concocted the following option.
> 
> Optically, I'd like your input. Here are the stats:
> 
> First Option: 8" F/6
> 
> Unit of Measure inch
> Primary Mirror Diameter 8.0
> Focal Length 48.0
> Focal Ratio 6.0
> Tube Inside Diameter                 9.25
> Tube Thickness 0.375
> Focuser Height 2.45
> Focuser Inside Diameter 2.0
> Focuser Extra Travel                 1.0
> Focuser Camera Travel 1.0
> Diagonal Minor Axis                 1.83
> Diagonal Offset 0.0762
> 100% Illumination Diameter                 0.3175
> 75% Illumination Diameter                 1.1788
> Front Aperture Diameter 9.1086
> Mirror Face to Focuser Hole                 38.55
> Focuser to Front End of Tube                 7.0
> Mirror Face to Back of Tube                 4.0
> Tube Length 49.55
> 
> 
> Basically, I'd like to know if this would be a
> functional scope to use
> for observing and basic astrophotography, and
> whether there are any
> potential limitations you can think of.
> 
> - Jake L.
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 



       
____________________________________________________________________________________
Need a vacation? Get great deals
to amazing places on Yahoo! Travel.
http://travel.yahoo.com/
_______________________________________________
ATM mailing list http://www.atmlist.net/