Re: (ATM) Coma and Telescope Design

[PFAFF2@delphi.com]

>  
> You may have trouble with tube currents with only 0.5" between
> the edge of the mirror and the velvet lining.  I would suggest at
> least 1.5 inch. With a 52" tube with a 9" id. (incuding the velvet)
> and 1.25 degree field of view, you are already vignetting 
> against the end of the tube.
> 
> Chuck
> 
> 
Good point I once built a 12.5" f4.0 Newt. in a 14" tube to make
the diagonal smaller. Tube currents are a big problem in this telescope.
Half the time the stars are tear drop in shape.
Bob Pfaff