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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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