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Jeremy,

I took the time to interpolate between your first and second Sun and
Moon altitudes. I then used the online calculator using interpolated
values for the altitudes and the time of each LD observation to
determine the error in the observed lunar distances which I found to
be:

3) 1.4
4) 1.0
5) 1.0
6) 1.2
7) 0.9

There has been a great deal written on this forum regarding issues in
observing lunars. I think it is fair to say that getting initial
results similar to what you have here is not entirely uncommon.

Some have found that they have had to "train their eye" so to speak by
predetermining an angle and seeing what the perfect alingment should
look like.

Since the results suggest about a 1' systematic error, IE is first and
foremost in question.

Did you have hazy conditions?

I think the list would agree that to get really accurate results,
conditions have to be perfect.

Otherwise, difficult to add much more. You may want to have a look at
some recent discussion on lunar distance accuracy as there is an
excellent posting from Frank summarizing sources of error.

Jim

On Jun 13, 4:15�am, Anabasis  wrote:
> � � � � �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
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