Re: ATM 6" f/8

[Larry Manuel <lmanuel@sprint.ca>]

 Dwight Elvey wrote:

>  So, in summary, you'd be able to see the rings on Saturn
> with the 7/8's secondary but not much of the Andromeda galaxy.

In my 6 in F/8 Newt, The focal plane was exactly 63 mm outside the light
path [Big Barlow just fit].  I used a 7/8 inch diagonal. and could detect
absolutely no vignetting at the edge of field of my 22 mm Panoptic [which
has 25 mm diam. field stop].  My calculations predicted about a 1 magnitude
light loss there - it sure wasn't visible to me.

I have a nice graphical spreadsheet based on Peters & Pike's [Sky & Tel
1977] algorithm for vignetting in the Newtonian focal plane which I will
share.

Larry.
--


lmanuel@sprint.ca
Larry [and/or Lynne] Manuel
Mississauga, Ont.

"Almost anything you do will seem insignificant, but it is most important
that you do it."
                                            --Mahatma Gandhi