An interesting shot Ric, did the object cross the meridian during the
exposure?

Personally, I use guidescopes exclusively. I have some perfectly tracked
exposures though of only one hour duration, pity the damn camera wasn't
focussed correctly - but I have some very sharp donuts! The 201XT I use
behaves much better with a guidescope than off-axis, and I can use much
shorter correction intervals with the bright, sharp star image. It's also
rare that for CCD use that any single exposure will extend beyond 10
minutes.

I have never seen the 'failured eposures' that proponents of off-axis guider
users use to condemn guidescopes as unreliable, so I don't know what
actually contributed to the star trailing. To those people - I would like to
see what you call a failure.

I believe I have a workable system using my guidescope setup, but I do not
have any long exposures to prove it. The only variable that I don't have
complete control over is the primary mirror moving within it's cell, though
I suspect that different examples of the LX200, particularly the larger 10"
and 12" models, exhibit considerable variation in the movement of the main
mirror. I do know that I have virtually zero image-shift when focussing at
high powers, but this is a separate (though related) issue, I think, from
the mirror 'flop' due to an insecure mirror. I do think that if your own
scope exhibits significant image-shift when focussing then there is a
mechanical problem with your scope that needs to be rectified before
attempting prolonged exposures using a guidescope.

Chris Heapy

> ----------
> Sent: 28 January 1999 05:18
> Subject: [M]: (M) Guider
>
> For anyone interest of a astrophoto of deep sky using a guide scope.
> This shot was near the American Nebula on hypered Tech Pan film for
> nearly 2 hours. The image is greatly enlarged to show detail. E-mail me
> with the supplied link of your thoughts using a guide scope instead of a
> Off-axis Guider.
>
> ric
>
> Photo at:
>
> http://members.aol.com/ceckers1/page/index.htm
>
> ___________________________________________________________________
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