NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Paul Dolkas
Date: 2013 Jan 21, 11:50 -0800
Frank-
What I did was to use the moon-Jupiter distance I observed (adding the moons SD & subtracting the Hp) to interpolate the UTC time from the Lunar Prediction tables. This of course assumed that I can do a strait linear interpolation, which as you point out, is probably only good for large distances.
For example, at 6:00:00 (UTC), Jan 21, the Moon-Jupiter distance was 10o 26.6’from your tables. At 7:00:00 it was 9o 57’. My observation was 10o 58.4’. Adding the SD (14.8’) and subtracting the Hp & index error (54.22’ & 1.5’) gave me a corrected & geocentric distance of 10o 17.5’. This is 30.74% of the difference between 6:00 & 7:00, or 6:18:29 UTC. Problem is, my observation was at 6:34:27.
I don’t know if this is standard technique, but I tried it out using the values for 5:00:00, 6:00:00 & 7:00:00. 6:00 is halfway between 5 & 7, and the 6:00 moon-Jupiter distance is pretty close to halfway between the 5 & 7 values, so I figured there must be something to it. Again, I think your point about linear interpolations being only accurate for larger separations is a good one.
As for instrumentation, this was done using my Davis plastic wonder, with a 3X scope. I took 3 shots, and they were all pretty close (11o 0’, 10o 58.4’ & 10o 58.4’ ). Time of shots were 6:31:39, 6:34:27, & 6:36:44 UTC. I’m sure of the times because I have one of those nifty watches (Citizen Navihawk) that synchronizes with the atomic clock.
I fed the numbers into a spreadsheet I ginned up, since I’m useless without one:
I’d love to know if I missed something. Then I can stop blaming the Davis…
Paul Dolkas
From: navlist-bounce@fer3.com [mailto:navlist-bounce@fer3.com] On Behalf Of Frank Reed
Sent: Sunday, January 20, 2013 10:17 PM
To: NavList@fer3.com
Subject: [NavList] Re: Jupiter and the Moon
Paul, you wrote:
"Last night & tonight’s Lunar shots gave pretty inaccurate results"
Did you clear them using my online calculator or some other approach? Could you post your observational data? And what sort of sextant, what scope, etc.? By the way, did you try measuring the Sun's diameter recently?
-FER
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