RE: Pictor 201XT
| Subject: | RE: Pictor 201XT |
| From: | Michael Hart |
| Date: | Thu Jul 18 17:18:14 1996 |
>getting one. I get the impression that those who have them are generally
>happy with them, yes?
Yes, the Pictor 201XT is what the Pictor 201 should have been. Most
seem to be happy with the Pictor 202XT.
>Would the 201XT work with a guide scope? I have an old Celestron C90
>spotting scope that someone gave me. It piggy-backs nicely and I have
>mirror diagonal that adapts it to 1.25". The focal lenth is 1000mm. Would
>this be a workable guide scope?
Id use a F/15+ guidescope with as couple of mounting rings on each end
of your scope. This "classic" approach allows for maximum stiffness to
avoid flexure problems that will probably result using the spotting scope
mounts. In addition, youll want 100-200X or better from your guidescope
and pinpoint stars- tougher to achieve with a spotting scope.
Another area of concern is the differential flexure of a SCT or Mak MIRROR
with your guidescope. The moving SCT and Mak mirrors operating at F/1.5
to F/2 are much more prone to alignment errors over a standard Newtonian
or refractor which is one BIG reason to stick with the somewhat limited choice
of stars available with off-axis guiding. Mirror shifting with your 7" Mak should
be minimal as compared to a larger SCT. With a larger SCT, internal
modifications are probably needed to prevent differential mirror flexure,
ESPECIALLY for those wanting a SCT or MAK (even better, if F-15) as a
guidescope. The required mods vary from scope to scope and are not for the
faint at heart, since youll have to remove your primary mirror, just for starters!
Then, you have to balance everything, which becomes a problem only dual axis
counterweights can solve with larger guidescopes. For large scopes, this
translates to big $$$.
Still, I prefer the large aperture guidescope approach which allows
framing of your image, then selecting a nice BRIGHT guidestar for the
Pictor 201XT that is in the plane as the Pictor 201XT was programmed.
You just center the guidestar on your reticle, using the rings, then insert
the Pictor 201XT that has been made parafocal to your reticle with stops
and extension tubes, and guide. No funny positions. Why, its so fun that
I frequently opt to manually guide over using the Pictor 201XT!
>Are there other autoguiders available besides the 201XT, other than CCD
>imagers?
>--
>Robin Casady
>http://www.casadyg.com
As for other Autoguiders, you can use ANY Pictor, even the imaging ones
and those from SBIG. With the ability to pick your guidestar, more expensive
autoguiders are probably not needed, so you can save money here.
Michael Hart
mhart@netexpress.net
