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Hi all,
After having dealt with lunars for quite some time I may provide some 
opinion about accuracies expected by skilled navigators:
- Maskelyne 1763 "within one degree". Seems realsitic due to less accurate 
ephemerids than we have today and also to less good measuring devices than 
today
- 1840-1850 "between 5 and 30 nautical miles"
- 1890-1900 "7-10 nautical miles"
All measured on the equator.
My own opinion is that the accuracy in longitude should be within 15-20 
nautical miles with todays ephemerids and tools.
The lunar distance method for finding GMT is indeed very senstitive. An 
error of one arc minute in the distance will give about 30 nautical miles 
error in longitude.
Kent Nordstr�m

----- Original Message ----- 
From: "Mike Burkes" 
To: 
Sent: Wednesday, May 28, 2008 8:50 AM
Subject: [NavList 5167] Re: A Lunar




Hi Jeremy, Mike Burkes again with my solutions of your Lunar as per Bruce 
Stark's Tables:
both Hc's are in agreement
corrected observation,D=40d 19.8m
my GMT per Lunar=08-13-26
true GMT              =08-08-40
difference              =00-04-46
My arc error          =2.7m
It seems our errors in time are different. I may be missing something but 
was there a reason for the height of eye data?
Mike Burkes
> Here is the data:n about 9
> 8 May 2008 08h 08m 40s UTC.
> Fix was Lat 14deg 48.3� N; Long was 145deg 45.0E
> At that time I calculated the sun�s Hc at 5deg 27.2� and the moon�s Hc
> at 45deg 08.1�
> I shot a near distance and obtained an Hs of 38 deg 56.4� IE was 1.0�
> off the arc, Height of eye was 106 ft.
>
> I used Frank�s webpage to reduce the Lunar and obtained a corrected
> observation of 40deg 19.2� and a calculated lunar distance of 40deg
> 17.1� for an arc error of 2.1�. Unfortunately, this lead me to an
> error in time of 3m 36s which is 1deg 02� of Longitude. I am guessing
> that the low altitude of the sun contributed significantly to this
> error as I have never had much luck with low altitude sun shots. I
> really should have thought of it earlier, and shot the distance when
> the sun was about 20 degs in altitude.
>
> I am wondering what people are typically getting for errors? I am
> thinking that this is a bit much and I think with a bit more practice
> I can do better.
>
> Jeremy
>
> >

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