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Re: Lunar trouble, need help
From: Kent Nordstr�m
Date: 2008 Jun 15, 10:32 +0200
From: Kent Nordstr�m
Date: 2008 Jun 15, 10:32 +0200
Hi, I will confirm George's view on measurement. In my calculation I have assumed that the LD was measured on the nearest edges on both the moon and the sun. This means that in the calculation the semi-diameters for both bodies have been added to the measured distance, for the moon +15m 25s and for the sun +15m 45s. The correction for 2nd differencies is -5.64 seconds (the corresponding difference in the proportional logartims is -18) Kent N ----- Original Message ----- From: "George Huxtable"To: Sent: Sunday, June 15, 2008 1:17 AM Subject: [NavList 5453] Re: Lunar trouble, need help I've been looking at Kent Nordstrom's Lunar distance calculation, without recalculating his results.. What Jeremy measured was the angle between the near limbs of the Sun and the Moon. What is predicted in the Lunar Distance table in the Almanac is the angle between their centres. Somewhere, then, there should be a step in the calculation in which the semidiameters of Sun and Moon should be added to the observed lunar distance. I can't see that step shown explicitly. However it might be included within Kent's "old fashioned way" of reducing the lunar distance. If not, it should be in there somewhere. George. contact George Huxtable at george@huxtable.u-net.com or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. ----- Original Message ----- From: "KENT AE NORDSTR�M" To: Sent: Saturday, June 14, 2008 7:46 PM Subject: [NavList 5451] Re: Lunar trouble, need help Jeremy asks for help. I don�t know if I can help but certainly provide some comments. The normalized values from Jeremy�s series of observations should be: - mean LD 86 d 10 m 18 s (same as Jeremy) - mean time for LD observation should be 06-22-59 (what type of time??) - the altitude for the sun to 06-22-59 should be 33d 07,43m - the altitude for the moon to 06-22-59 should be 61d 19,3m After reduction of altitudes and distance (my old fashioned way) is obtained: - moon 61d 20m 52,6s - sun 33d 11m 43,57s - distance 86d 14m 45,64s At GMT 0600 the true distance is 85d 31m 59s At GMT 0900 the true distance is 87d 01m 05s At GMT 1200 the true distance is 88d 29m 50s Consequently the measured truse distance is between 0600 and 0900. The GMT for the measured true distance (incl. The correction for account of second differencies) is 07-26-17,74. Regards Kent N ----- Original Message ----- From: "Anabasis" To: "NavList" Sent: Friday, June 13, 2008 10:15 AM Subject: [NavList 5413] Lunar trouble, need help I am having a bit of trouble with a lunar I shot this week at sea. It was late afternoon and I tried for a more �traditional� lunar. I shot an altitude of the sun, then the moon, then 5 lunar distances, followed by another sun and finally another moon altitude. (in retrospect, I should have shot the 2nd moon first then finally the second sun) My first trouble was with the moon altitudes. The Hs of the sun was nearly 2x and on opposite bearings as the moon so I was getting massive flashes of the sun where it hit my horizon mirror and bounced back through the scope. I have a feeling that my altitudes of the moon are none too accurate. Here is my data around 0620 on 10 June 2008. 1) Sun LL: Hs 33deg 58.5� @ 06h 19m 13s UTC 2) Moon UL: 60deg 36.8� @ 06h 20m 44s 3) LD1: 86deg 10.3� @ 06h 21m 40s 4) LD2: 86deg 10.0� @06h 22m 20s 5) LD3: 86deg 10.2� @06h 22m 52s 6) LD4: 86deg 10.6� @06h 23m 24s 7) LD5: 86deg 10.6� @06h 24m 39s 8) Sun LL: 32deg 35.8� @ 06h 25m 19s 9) Moon UL: 61deg 49.2� @ 06h 26m 28s DR (didn�t take a fix) Latitude was 15deg 14.0�N and Longitude was 144-04�E. Ship was on course 270 at 12.0 knots. IE was 0.0 T/P was 98deg F and 1010MB. Height of eye is 106 feet. I averaged the two sun lines to get 33deg 17.2� at 06h 22m 15s, then the two moon altitudes to get 61deg 13.0� at 06h 23m 37s. Finally the 5 LD�s averaged to 86deg 10.34� at 06h 22m 59s. I had trouble when I used Frank�s online calculator where I input the three mean sight numbers and used the mean LD time. Then I used the near limbs I got an error of over 35� of arc. This looked an awful lot like the two semi-diameters added together, so I substituted far limb for near and got a LD error of 0.9� which seems more reasonable. Something is amiss, and I don�t know enough about shooting lunars to know what is going on. Can anyone help me out here? Jeremy -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 270.3.0/1502 - Release Date: 6/13/2008 7:25 PM --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---