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RE:
http://www.fer3.com/arc/m2.aspx?i=115703
[NavList] Re: Friendly challenge : Jupiter Lunar Exercise 09 Feb 2011
From: m_burkes---com
Date: 19 Feb 2011 14:04

Hello Mike,

Moon and Jupiter Azimuths were "nearly" parallel, as far as I can remember (I'm not home tonite), and this is why I shot a Sun Azimuth about one hour and half earlier, with a "just minimal" cut angle of some 30° which is better than nothing. I was sure to get the Sun, so I took no chance : I shot it very carefully 5 times the best I could under excellent weather conditions. I did not care at all about "Position accuracy degradation due to DR" on that evening since I was a NON MOVING Observer.

This 30° cut angle is already sufficient to establish quite reasonable results, since 5 of us so far have derived Fixes within 3 miles from one another and within 5 miles from true position, through 5 different methods, which is quite interesting.

That evening I choose no additional Body, and there was really no solid reason for doing so. And also from where I was shooting, Sirius and a few other stars were over the land.

On the other hand I am not familiar with M. John Letcher's "Moon LOP GMT method", or with the "Lunar Distance method of GMT" which you mentioned and suggested in your Post. I would therefore leave it to more experienced and knowledgeable NavList Members (may Frank E. Reed ?, or somebody else ?) to appropriately comment on your suggestions and/or queries.

How about all of us discovering about a sixth different method from you since you are considering working this example ?

*******

On the other hand, 3 Days Later, for my "[NavList] 12 Feb 2011 Unorthodox Jupiter Lunar from a moving platform" (http://www.fer3.com/arc/m2.aspx?i=115688), I was under a quite different environment, i.e. on a (fast) moving platform which had covered some 30 miles between the first Sun Observations and the last series of Lunar Distances. I might have been under less favourable conditions than 3 days earlier, however (i) the cut angle between the Sun and the Moon was much better : close to 90° as I can recall, and (ii) I had the chance of observing from a steady ship with an excellent bottom track following capability, which in fact (very) significantly reduced inaccuracies of DR over (long) distances.

Good Luck and

Best Regards

Antoine M. Couëtte

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