"Alan W. Craft" wrote in message
...
On Thu, 24 Jul 2003 08:40:04 +0000 (UTC), William Mc Hale
...reflected:

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?

"Fast" and "slow" are borrowed from the world of photography
in which the speed of a lens (the amount of time it takes to record
an image of proper exposure) is determined entirely by its f/number
(assuming there isn't a filter or obstruction in the light path.)



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.

No. Exactly the opposite. Speed relates to how much light a lens/mirror
can pour into a given small area at the image plane. An 8" would be able
to put four times the amount of light that a 4" could deliver into the same
area.



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


Again, please find and read the Sky and Telescope article. There are many
other
factors than just scope speed.

Cheers,
Larry G.