Re: [M]: Lx200 Mirror Flop/Slop
| Subject: | Re: [M]: Lx200 Mirror Flop/Slop |
| From: | R. A. Greiner |
| Date: | Thu Apr 01 17:16:52 1999 |
cfrye@ix.netcom.com wrote:
> I tried my ST-4 with an OAG, which I do not recommend, it is very hard to
> achieve simultanious focus with the main imaging camera (MX5-C in my case).
>
> When my LX200 10" mirror "flopped", the ST-4 lost the guide star, it completly
> left the CCD chip. Upon subsequent analysis, I found that my main mirror "flopped"
> around quite a bit.
>
> Is there an advantage to OAG vs. Guidscope if the main mirror changes position
> so much that the guide star is lost?.
You have hit upon a problem that is a serious one for many persons. If there is flop
in any part of the optical system, usually the main mirror, which is so large and
sudden that you loose the guide star, you are out of business completely.
I had this problem when guiding with the 216 chip which is also quite small while doing
piggyback photography. The chip was at prime focus. When it held guiding it was
wonderful since the focal length of the LX 12" is 3000 mm and that of the camera
telephotos 1/5 of that. One hour exposures were easy. But sometimes the chip lost the
star. I fixed this problem by using the locking bolt. For long focal length
photography, with hour long exposures, the problem is not only losing the guide star
but even tiny shifts in the guide star image.
Sudden shifts must be controlled in the first place then the smaller shifts due to
flexure need to be controlled. I would take it a step at a time.
Doc G
