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Subject: Re: astrocompass still in use
jcs@XXX.XXX
Date: Thu Sep 26 2002 - 20:15:46 EDT
Quoting Paul Hirose <paulhirose@XXX.XXX>:
> The astrocompass lives on. A major utility company in California
> allows engineers and architects to borrow one to evaluate solar access
> to a building site. Here is their online manual:
>
>
http://www.pge.com/003_save_energy/003c_edu_train/pec/toolbox/tll/app_notes/astr
o_comp.shtml
>
I have an Astrocompass and I have fixed up a mounting on my boat for it. I used
it about a year ago to check the Deviation of the boat's compass and a very
interesting afternoons exercise it was too. I wonder if anyone else has found a
use for this old faithful.
First the instrument was mounted and levelled. The Latitude was set on the
micrometer scale and the Declination of the Sun set very roughly on the
sighting bar. The LHA of the Sun changes slowly so I wrote a simple program on
a Ti82 calculator to give the value to set on the LHA drum for every minute of
time and this was re-adjusted accordingly.
Next the boat was carefully steered on 12 different COMPASS headings at 30
deg increments and the Astrocompass rotated to bring the Sun's shadow of the
sighting bar onto the plastic graticule. At this point the TRUE direction of
the boat was read of the base scale. Adding Variation to this data produces a
list values for plotting the Deviation correction graph.
I have no idea of the origin of this instrument and I would like to hear if
anyone in the group does. I was taught how to use it in a Coastal Command
Lancaster many years ago and my instructor then had used one when flying over
the Libyan dessert during the war. His magnetic compass had been destroyed by
an enemy bullet.
I have an instruction book. If any one would like a copy my email is
jcs@XXX.XXX
Clive Sutherland.
Wantage, (where King Alfred burnt the cakes).
51deg 38.2 min N 001deg 24.5min W
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