"Steve" wrote in message
.net...
Has anyone in the group have experience using the new digital Dobs by
Orion?
How do they compare to similar versions of Celestron and Meades GOTO
models?

Comparing a Celestron 8" SCT with Starbright, to an XT10 Skyquest from Orion
(the older Guan Sheng model). The 10" is brighter, provides better
resolution, and has better response to low contrast details on Mars and
Jupiter. That said, the difference in each case is really marginal, and more
dependent on atmospheric conditions than scope specs and design. When
atmospheric conditions are good for observing, both scopes perform
admirably. The one place where I've seen the XT10 provide an appreciable
improvement, is in drawing out spiral structure in M51 under my local
conditions, as well as allowing easier detection of other objects with low
surface brightness (such as M101). But that's simply a result that a 10"
aperture of any other design would also provide.

Based on the comparison of these two scopes, I would venture a reasonable
guess that a 10" SCT would outperform an 8" F6 Newtonian in brightness and
contrast, and that an 11" SCT would beat a 10" Newt in brightness and
contrast, by a nose. (I'm not promoting one over the other on optics, btw.
As far as I'm concerned, the choice between an SCT and a Newt or Dob of
similar aperture should be made on a combination of things including mount,
portability and versatility. Buying an 8" Newt OTA strictly to outperform an
8" SCT optically is, IMO, unreasonable considering the minimal differences.)

That said, you _will_ need a little more aperture in the SCT, to compensate
for the loss of light on each surface, and to make up for the larger CO. But
again, we're really splitting hairs.

As for the difference between a GoTo and DSCs, I prefer DSCs and an EQ
mounting. They are virtually noiseless, and for visual use provide every bit
the needed accuracy. Add an EQ Platform to a Dob, use a GEM for a Newt or
SCT, or a Fork/Wedge for an SCT, and you have all the function of a GoTo.
There's really only one place where the GoTo is of unquestionable value to
the visual astronomer (although being this is saa, someone will no doubt
object), and that's with an altazimuth fork or Dob mount, since motorized
tracking is then possible.

If you are seriously considering the Dob, buy it because you want a Dob, not
because of any techno gadgets that apply. You will still have to hand-track
using the Dob with DSCs, and tracking is a much larger issue than finding,
IMO.

IOW, based on my current exeperiences with Dobs, Forks, Wedges and GEMs,
given the choice between a Dob with DSCs and a Dob with EQ platform. I'd
definitely go for the one with platform drive. Finding stuff is a pain, but
no where near as much a pain as hand tracking easy to find targets above
some threshold of magnification (in my case, I get annoyed above 150x).
Lastly, with the platform drive, you don't lose your position if you need to
spend time studying the charts during a star hop. That makes star hopping
less of a pain, thus the DSCs less of an advantage.

Stephen Paul