On Monday, June 29, 1998 8:18 PM, Jerry Mulchin wrote:

> To all on the list,
>
> Before I step into the Meade Miar again, I would like to ask if anyone
> on the list has any experience with the LX200 16" scope.
>
> I currently have a LX200 10 inch and have had nothing but problems with
> the DEC assembly (Doc G. knows of what I speak), and mirror shift. I've
> even rebuilt the DEC assembly, but "you can't make a silk purse out of a
> soughs ear", if you know what I mean. I do CCD work and the scope is not
> always up to the task even with the AO-7.
>
> I have the following questions:
>
> 1.) Are there problems with the DEC assembly on the 16"? Does ir take
> more than 15 seconds to start moving the scope when in Guide mode?
>
> 2.) Mirror shift I can put up with to some extent, how does the 16"
> compare?
>
> 3.) Vignetting is a real problem with my ST-8 and the 10". The light cone
> looks like a bell curve on my flats. How is the 16" in this area?
>
> 4>) Is there anything else I should be aware of on the 16" as far as
> problems?
>
> I thank all those who respond in advance.
>
>
> Jerry Mulchin
> Programmer, Amateur Astronomer
> Astronomy Web Page www.astroguy.com
> "It is never wrong to ask a question, it is always wrong to be ignorant."
>

This post saddens me. Not because of the interest in purchasing a 16"
LX-200, (or the decision in a bit over 24 hours to purchase another scope),
but for the apparent reasons for buying a new mount and scope- the Dec drive
and mirror shift. Perhaps I have spent too much time engaging in Dec drive
and mirror shift discussions. I must assess whether the efforts of writing
and posting detailed procedures are better spent elsewhere.

I am extremely disappointed many rather time consuming posts pertaining
to this area may still be inadequate, in spite of several revisions and
considerable effort put forth by myself, Doc G and others to outline solutions
for those with more demanding requirements. Many of those discussions
include illustrations and are outlined on Doc G's Info Page and Ed Stewart's
Topical Archives. I must encourage those with questions in these areas
to seek out ALL discussions on these aspects as I believe many have
made and continue to make rather important contributions and observations.

I am astonished that with all the detailed information on the Dec assembly,
a relatively simply solution is not close at hand for Jerry, especially with so
many knowledgeable folks on MAPUG. I had thought that by now, extreme
Dec movement delays suggested by Jerry would be eradicated for those
with desire and reasonable mechanical abilities. Perhaps I have failed to
adequately explain the procedures.

As I write this, I have just finished a fantastic night of viewing and imaging
under good seeing. My tweaked 12" LX-200 on the Giant Field Tripod and
Super Wedge performed wonderfully. Dec reversal time is 1 second using a
10 backlash setting. There is NO retrograde motion at 800X. Dec direction
changes are smooth and precisely controlled- no sudden jerks at 800X upon
Dec reversal. Mirror shift remains at 13 seconds near the horizon and 3-4
seconds above 40 degrees altitude. The PEC continues to perform as usual-
4-5 seconds peak-peak periodic error. Pointing accuracy remains very good
in the alt-az mode- 0.4 to 1.8 arc minutes throughout the sky in the non
high precision mode. The optics easily perform to the seeing, providing
exquisite views of Jupiter and Saturn at 800X.

But can the LX-200 image? Tonight, I completed a 3000 mm tricolor image
of M-57 (without the AO-7) exceeding the best results I have ever obtained
on this object. The minimum tricolor exposure time was 20 minutes. What
is interesting is the level of detail in this object and the rather large spiral
galaxy (about 1/2 M-57's diameter) near it. No flip mirrors are needed with
the available LX-200 pointing precision. I am quite comfortable using my 12"
with the factory moving mirror focuser.

Now, I know many MAPUG members may be worried as they cannot afford
to spend over $10,000 for a mount and scope for astrophotography. I have
worked on several LX-200's and find them quite similar in mechanical
construction and milling precision. I believe that with a bit of desire, some
elbow grease, utilization of other's experiences, and a little luck, others can
obtain the results and enjoyment I have obtained from my 12" LX-200 sows' ear.




--
Michael Hart
Husen Observatory

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