Re: C11 Mirror dance

Hi
Normally I would be able to help but I am in the middle of a house
remodel. However, while I cant tear it down for you, I can assess it if
you would like to bring it over. I am in Los Altos.

Typical mirror flop from focusing is about 30 sec to 1 min of arc. Have
you assessed it in that manner?? Jupiter is about 45 arcsec in diam at
opposition. The method to elminate focusing flop is to always "end"
your focusing action by moving the primary "up" the tube (forward). This
may mean you have to come back and approach focus a couple of times until
you hit it just right. But after awhile that will become second nature.

Maybe we can determine if it is "normal" mirror flop or something else.
It is not unknown for the cork spacer associated with the primary mirror
to shrink and allow a bit more flop than normal. This is fixable by
tightening the retaining nut in front of the mirror.

You didnt mention how old the scope is.

Contact me off-list if you would like to schedule a time to meet.

---------
Phil Chambers [ptchamb-at-svpal.org] (S.F. Bay Area - Calif. USA)

On Mon, 12 May 2008, RBA wrote:

> My C11 suffers from mirror flop - not a great deal to get somewhat OK focus,
> but serious enough to make accurate focusing a daunting task. I fact, ligthly
> knocking on the tube already makes the mirror dance a bit (even it does end
> up in the same place all the time), so I'm not sure I'd call this just a
> "mirror flop" or something else.
>
> Before sending it to Celestron, does anyone know someone local who might have
> experience taking a C11 apart and getting this kind of problems fixed or at
> least improved? I'd be happy to pay a fee for the job of course. Or any hint
> about how to "DIY"?
>
> Thanks,
> Rogelio
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