Re: ATM Rich Field scopes

["Mark St.George" <sanjo@execulink.com>]

Hi Clive and everyone,

I have been catching up on a couple of weeks of e-mail backlog and just came
across
your message.

Boy oh Boy!!! Was I ever freaked when I saw that you started an RF Binoscope
thread!
Believe it or not, I just recently started working on designs for an RF
Binoscope
in the 6 and 8 inch sizes!  

Presently, I am deciding between a 6 inch f/3.5 Binoscope and an 8 inch
f/3.0 Binoscope. Since they would both possess a 40% obstruction (a necessary
evil due to the 3.5 inch long focuser required), I am leaning slightly
towards the
8 inch f/3.0 because of its greater light gathering ability (which effectively
equals almost 3 extra inches of aperture) and reasonably large FOV (only 0.4
degrees smaller than the 6 inch f/3.5 FOV).

>    And thirdly, for those with the cash to burn..... design the (binocular)
>RFT around a pair of 22mm Naglers... this dictates an unfriendly system f /
>ratio, but not an impossible one... f / 3 or there abouts...

Have you successfully used 22 mm Naglers in a Bino configuration? If so,
then I greatly envy you!!!!! 

To date, I know of only one gentleman (who will remain anonymous to protect
him from extremely jealous astronomers :-)) who is able to view
through two 22mm Naglers, as well as the larger 20mm Type 2 Naglers
and 35mm Panoptics, because he possesses 84MM EYESPACING. Since the
22mm Nagler body diameter is 2.4 inches, I calculate that it would 
require a minimum 75mm eyespacing to properly use a pair.

For those of us who are not "gifted", like the aforementioned gentleman, 
I would recommend using 27mm Panoptics as low power RF Binoscope
eyepieces for two reasons:

1) The 27mm Panoptic body diameter (2.1 inches) is small enough to
allow a users possessing 62-63mm eyespacing (within the range of 
many adults) to use two of them in a RF Binoscope. For example,
I have an eyespacing equal to a tad under 64mm and I am just able
to place my nose in between the eyepiece bodies with my eyes seated
against the eyecups (19mm eye relief).

2) The 27mm Panoptic's field stop is 30.5mm compared to the 22mm Nagler's
field stop of 31.1mm, displaying a virtually identical FOV at the 
expense of slightly lower magnification.

Onto another issue....

How bad is coma visually in f/3.0 system at low power? I have no experience
beyond anything faster than f3.8.

I initially thought about using Paracorrs, but almost 3 inches of it
must sit inside the focuser tube (requiring me to lengthen my focuser by
2 inches) and that is not very desirable. 

I guess home-made Ross coma correctors are one option.
A Mak-Newt design is another option. :-)
 
Any thoughts?

Regards,
Mark St.George