"Diregolo, Joe" wrote:

> I'm off center about 1/4" in the fork direction. Still I get good
> tracking of unguided CCD images for about 5 min.
>

I'm new to this group (and amateur astronomy) and you're above comment got me
thinking about unguided vs. guided CCD images. I assume you're running your
scope in polar mode (i.e. using a wedge) but, still, 5 minutes seems pretty
good based on other's comments. It's certainly better than in alt-az mode.
But how would running the scope in alt-az _with_ a guider compare against
running the scope in polar mode unguided?

I suppose with a wedge you can eliminate most if not all of the movement in the
declination drive, but with the feedback/correction of a guider in alt-az mode
does this really matter? I mean, were the correction perfect (which I realize
it's not, but it just might be "good enough") the only drawback I can think of
is field rotation. Again, being new to astro stuff, I don't think I fully
comprehend the significance of field rotation with respect to how long that
effectively limits CCD exposure time. I realize that it does limit exposure
time, but how long of an exposure is practical? And even so, couldn't that
time be "extended" through "stacking" of multiple sequential images after some
rotation and registration? I mean, this last part is relatively cheap compared
to buying a wedge, it's just some math and software to write -- a software
pseudo field derotator.

Okay, now what's wrong with my novice thinking above? Go ahead, be brutal; I'm
braced for it.

I'm asking this question since (surprise) I was about to purchase a wedge and
thought maybe I could avoid the $550 purchase. And, yes, I'm cheap 8^)

Thanks for any comments,
bill

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