Re: ATM Large-format focus devices

["Bob May" <bobmay@nethere.com>]

The largest that I've seen have been 2.6" ones for some obscure telescope.
I'll note that for my 17th century refractor, I made up some eyepieces from
3" tubes which have a clear aperture of about 2.7" or so.
You will have to sort of do the same and I'd suggest that you consider a set
of longer FL ones of the Erfle or Orthoscopic designs for best results.
Anything under about 2" of FL can be considered as short and can be done
with 2" eyepieces.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net