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From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: Constant Frequency at LOW temperature
References: <3DC53B22.email@example.com> <3DC543F3.8C692E48@webaccess.net> <3DC54ABE.firstname.lastname@example.org>
Date: Sun, 03 Nov 2002 16:50:39 GMT
NNTP-Posting-Date: Sun, 03 Nov 2002 08:50:39 PST
Rene Tschaggelar wrote:
> Chuck Simmons wrote:
> > Rene Tschaggelar wrote:
> >>AFAIK, the earth rotation is not that constant over the day
> >>as it may be assumed. This is dues to the gravitational field
> >>of the moon and the uneven mass distribution of the earth.
> >>I couldn't put a figure to it though.
> > That is down in the mud compared to important effects. The earth rotates
> > once on its axis every 23 hours, 56 minutes and 4 seconds. Using that
> > approximation alone is good to 8 arcseconds per day. Taking into account
> > the once every several century adjustment of the leap year, I could have
> > given you a more accurate figure.
> I didn't mean the slowing down, rather the jitter in revolution speed
> during one day. But this number may also be very, very low.
That's way down in the mud. For example, some telescope makers prefer
that the polar axis be aligned to the true pole and some prefer the
rafracted pole. That is at least an order of magnitude bigger effect at
BTW, I have a good friend that contracts tracking system retrofits to
observatories and occasionally builds a telescope for a rich amateur. He
and I argued for years about using stepper motors (I said that they were
pretty worthless given his demand for quality). He eventually listened
and now ships retrofits for some of his old stepper installations.
Steppers have a very unfavorable torque characteristic for telescope
drives and cannot be considered for high qulity systems given the
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons email@example.com
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