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I recently contemplated starting a topic under the title
"Did lunars really qualify for the Longitude Prize"?
The condition of the prize, if I remember correctly was
to find a reliable method of determining longitude with
30' precision.
Can one really guarantee this with lunars?
You have to be able to measure distances (sometimes large)
with better than 1' accuracy.
(With all this irradiation, collimation
and other sort of corrections).

I measured quite a lot of lunar distances from my balcony, under
best possible conditions with a modern sextant, which most
rate as very good, using computer reduction.

My conclusion is that I am reasonably confident in 1' accuracy
(of the distance) but not much better. Some of my lunars are
0.6 and even 0.7 off.

Second, as we know from the Lewis and Clark story,
even professional astronomers/surveyors had difficulties
with reducing the sights.

I usually do this with Frank's calculator, and have my own
running on my computer and giving similar results.
Only once I tried to reduce a lunar observation "by hands",
but still using a primitive electronic calculator.
My experience shows that this is not easy:-)

On Sun, 5 Dec 2004, Frank Reed wrote:

> Any thoughts?

   

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