On Friday, August 07, 1998 3:47 AM, J Nordby wrote:

> One way to get changes/improvements in LX200's is to challenge the
> company by mentioning viable alternatives such as shown on Mel
> Bartels' excellent web site (previously mentioned here) as well as
> others. People out there have giant Dobsonians operating with better
> features than the LX200's themselves, responding to LX200 commands,
> tracking accurately, able to be slewed manually as well as by
> computer, tracking so well that CCD images can be made without guiding
> - it's quite amazing. One thing I found very compelling was the story
> of one telescope out there where, if you happened to bump it and it
> lost the object, it automatically slewed back into position. Try that
> with an LX200?!? Also it's a way to satisfy both your aperture fever
> and your love of LX200 technology.

<<snip>>

I own a very nice computerized dob. It required considerable skills
and custom work, which is not unusual. My dob is not my choice for
long exposure film imaging or high resolution CCD imaging. Yes, CCD
exposures can be made without guiding. Typical imaging consists of
multiple 1 minute exposures added together (typical values for large
computerized dobs). However, four, five, and even ten minute unguided
exposures can be had on average to moderately priced equatorial mounts
that are accurately polar aligned with the aid of a well programmed PEC.

While advances have been made in large amateur Alt-Az mounts such
as described above, they have certain limitations not found in conventional
equatorial mounts such as the LX-200. Exposures over 5 minutes are
always a challenge, which might explain why we don't see a plethora of
long exposure film images made from a 20-30" dobs.




--
Michael Hart
Husen Observatory

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