Re: ATM 16" F/33 valid design?

[Dominic-Luc Webb molmed <Dominic.Luc-Webb@molmed.ki.se>]

On Tue, 15 Jan 2002, Andy Saulietis wrote:

   > A 5x Tele-vue barlow would be a *lot* easier & have a
   > shorter air path thru the OTA as well...I considered
   > making a Herschelian (concave secondary) for my 32"
   > but will go with barlow instead.

Always nice to hear from you, Andy. I guess for that
matter, one could even place a 2X Barlow closer to
the primary (i.e., within the tube), between the
primary and secondary. Is there anything you can
think of to be gained from the F/33 Cass design? I
saw it more as novelty item than truly practical. Again,
I have not had good enough seeing most nights to make
any use of this anyway, and besides, I own a Barlow.

I still have not examined the math on this, regarding
light loss. In these simpler designs, at least, there
would presumably be a point at which so much light
is is lost, that even Jupiter or Venus would be too
faint to see or require lengthy imaging exposures. In the
case of Saturn, I suspect the view with the 16" F/33 scope that
Schaefer had was already getting pretty faint. This was in fact
part of why I was surprised he was able to see something
like the F ring. When I read this, I questioned whether the
F ring would even be bright enough to see with the eye.



Dominic

North 59 37' 30"
East  17 48' 10"