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On Mon, 22 Oct 2007 16:36:43 -0600, Greg R.  wrote:

>> I use the inverse of your method, I start counting seconds from the
>> time of the sight until I can look at my watch, never more than 3
>> seconds so less opportunity for the count to get off by any
>> significant amount.
> Ditto that, with the added step that I've timed how long it takes me to
> move the sextant away from my eye and read the watch (seems to be
> pretty consistent at 2 seconds), though I do count time the same way
> that you do.
>
Greg,

For Azimuth by the sun using a theodolite on land:

I follow the sun with one crosshair using my right hand, waiting for the
sun to move into the right position on the other hair.   When the
(Reoloffs Solar prism) diamond in the center is cut into four by the cross
hairs, I click the button on a split time stop watch with my left finger,
stopping the time and my right hand finger motion on (usually) the
vertical slow motion adjustment knob.  I write the stop watch time in the
proper column of the notebook first thing, just to make sure the watch has
actually stopped.  I check the watch against the written figures, and
restart the split time.

Then I enter the theodolite's V and H readings into their columns.  I do
another two shots the same way, transit the theodolite and do three with
the telescope in the face right (inverse) position.  Back to the reference
mark for the final check (should be 180 degrees off the first reference
reading plus or minus a few seconds) and the first set of sights is
recorded.

Depending on the accuracy required, do three or more sets starting at a
(specified) different position on the horizontal circle, and do your
calculations.  You need to know your Lat and Long quite closely, but
scaled off a topo map or GPS is good enough.  Declination at 0 hours and
24 hours, as well as GHA 0 and GHA 24 are required from a ephemeris, time
at stop watch zero can be from radio (where the double ticks can be
counted after the minute tone) or a radio updated clock.  Ten minutes with
a programmable calculator like the HP-48, and there should be a nice
cluster of points for your azimuth from your station to the reference
point.  I use a Wild T1A or  a Wild T2 with a Wild - Roeloffs Solar Prism,
so I easily can plot both Vertical angle and Horizontal circle reading for
each shot against the time.  Both should show very slight curves, ideally;
but if the calculated aximuth for each shot is plotted, there should be a
small random distribution about a median value.

If there happens to be a slope, showing the Az changing with time, and the
value seems out by (say) ten degrees; first thing to check would be that
you entered the sign correctly on your declination values.

--
Richard . . .

Using Opera 9.2.4 after the "Dog" died

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