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    Re: Aligning a transit telescope to the meridian
    From: Greg R_
    Date: 2008 Apr 21, 16:49 -0700

    > First would be use Polaris, of course. But given that a transit
    > telescope looks South, it may be inconvenient to use Polaris -
    > especially at these high latitudes (Scotland)
    
    I'm not sure how a transit telescope is aligned in the real world, but
    how about using Polaris to establish a true north/south line (with the
    appropriate corrections from an almanac, etc.), then using something
    like a surveyor's rod setup on the south side of that line to setup the
    'scope facing true south?
    
    Sounds like an intuitive solution to me, at least...
    
    --
    GregR
    
    
    --- Geoffrey Kolbe  wrote:
    
    >
    > With the recent discussion on the abolition of the leap-second and
    > the
    > problems of Delta T, I have been pondering the possibility of
    > measuring
    > Delta T myself.
    >
    > The transit telescope was invented by that Danish polymath genius Ole
    >
    > Roemer in about 1675 and quickly adopted by Greenwich and then by all
    > the
    > world's observatories as a means to determine time. So, this seems a
    > good
    > way to go. But the main problem would be setting the telescope up so
    > that
    > it was aligned to the meridian. With a transit theodolite - which is
    > essentially a portable alt-az telescope - one can easily time the
    > moment a
    > star or the sun transits the vertical cross wire in the telescope.
    > Using
    > the calculated azimuth of the sun or star for that moment, it is easy
    > to
    > correct the plate azimuth of the theodolite and swing it around to
    > the
    > meridian. But, since I want to use the telescope to measure time, I
    > would
    > prefer to find some other way to set it up which did not involve the
    > use of
    > absolute time.
    >
    > It seems that in England, there was a flurry of interest in small
    > transit
    > telescopes in the late 19th century as country gentlemen and the
    > newly rich
    > industrialists needed some way to determine the time in their country
    >
    > estates. To this end, a book called "A Treatise on the Transit
    > Instrument
    > as Applied to the Determination of Time" was written in 1882 by
    > Latimer
    > Clark. Unfortunately, although Google books tantalizingly lists the
    > contents of the book, it does not seem to be available.
    >
    > There are a couple of ways that I can think of. First would be use
    > Polaris,
    > of course. But given that a transit telescope looks South, it may be
    > inconvenient to use Polaris - especially at these high latitudes
    > (Scotland). Second would be to time the transits of two stars of
    > preferably
    > similar SHA but greatly differing declination. Only if the telescope
    > is
    > aligned to the meridian will the difference in transit times be
    > correct.
    >
    > Can anyone come up with any other ways to align a transit telescope
    > to the
    > meridian, which does not involve the use of absolute time?
    >
    > Geoffrey Kolbe
    >
    >
    >
    >
    >
    >
    >
    >
    > >
    >
    
    
    
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