On Thu, 24 Jul 2003 08:40:04 +0000 (UTC), William Mc Hale ...reflected:

LarryG wrote:
"Alan W. Craft" wrote in message
...

I'm considering a Parks classic Newtonian,
and to mount on a Vixen GP-DX equatorial
mount. While their 8" f3.5 seems to be just
a wee bit too fast, and their 8" f6 a tad too
slow for DSO's and the like(not to mention
the tube length), I've looked into the
possibility of an 8" f5 custom-made by
Parks and sold via Scope City...

Check out the recent issue of Sky and Telescope about observing DSOs
and the merits of high or low magnification. "Slow" scopes are fine for
many such objects. The conventional wisdom dictating fast scopes simply
doesn't hold up in practice, once the other variable of vision and observing
are factored in.

Not to mention that f/6 is not really all that slow. On an 8" one could
get about 2 degrees out of a 35 mm Panoptic.

Correct me if I'm wrong, but shouldn't the focal length of the telescope
in conjunction with the f.l. of the eyepiece, that is, the magnification,
determine whether or not a telescope is fast or slow?

While an 8" f6 would be considered fast when compared to an 8" f10,
the same 8" f6 would at the same time be equitable in "speed" to a 4" f12,
and therefore considered slow.

Such slowness is precisely what I am trying so desperately to avoid,
and in order to use the telescope for comet-hunting and widefield DSO
observation, while at the same avoiding glaring instances of coma
and exacting collimations.

Please excuse my ignorance on the matter if I've overlooked something.

Alan