Re: Telescope resolution.

CeeBee wrote:
> > Also, is it possible to resolve the Encke division of Saturn with a 10"
> > Newt? I thought I could just see it last night in short moments of
> > excellent seeing.
>
> In theory, yes. Resolving power: 4.56 divided by the aperture of 10" =
> 0.456 arcsecond

But the Encke division has a much smaller width than 0.456 arcsecond.
That is closer to the width of the much larger Cassini division.

In any event, the issue is not whether you can resolve the division as
a distinct band, as opposed to a thin line. We will be satisfied as a
matter of course with simple detection. Thus, we can detect phone lines
from a great distance away, even though their angular width at that
distance is much smaller than the eye's ability to resolve (typically
about one arcminute without any optical aid).

That is not to say that extra aperture won't help, since diffraction
effects will continue to smear the contrast, and the smaller the
telescope, the greater the smearing, and the greater the likelihood that
the smearing will be so intense that the contrast will be altogether
undetectable.

I have heard of observations of the division, as opposed to the minimum,
in apertures as small as 8 inches, but I think that such observations
are very difficult to obtain. Even with much larger apertures--12, 14,
16 inches--where detection would be much easier, you are still at the
mercy of atmospheric turbulence. Turbulence does occasionally settle,
of course, so one more piece of advice I would add is to be very patient
indeed (and the larger your telescope, the more patient you should be).

--
Brian Tung <brian@xxxxxxx>
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.