Re: ATM Focal ratio/length question

["Bill T." <twentiethwave@hotmail.com>]

Guy Brandenburg wrote:
> I certainly discovered that my 8" f/6 was way too low to the ground for
> me. I had to raise the altitude bearing up higher to make it comfortable
> to use.
> But mostly I prefer looking at deep-sky stuff, not planets; I am not
> sure I would like the extra length of a 64" + long tube (i.e. 8" f/8).

>From the point of view of observing deep sky objects, there's no inherent
disadvantage to f8 over the more common f6 or so.  Arguably, the typical f8
will often exhibit better contrast than a shorter f-ratio, and IMHO is
superior for all observing applications, including rich field (you'll need a
good 40mm for an f8, vs. a 30mm for an f6, but the field of view will be the
same).  64" is far from a truly long focal length.   An f8, 8" tube can be
stuffed at an angle into most compact sedans, or extending from the front to
back passenger seats with the front seatback all the way down.

Bill T.