Talk:Lunar distance (navigation)

message: Tried to explain this back in November but had it deleted by someone who simply proclaimed that they couldn't understand it. Hopefully this works better!
:Apologies. I know how you feal - I've had it done to me! 
:After I read the article it took me a while to work out what it must have been saying, and when I finally worked it out, the explanation was so different I couldn't just edit it!
:I see you didn't massacre my own contribution, so hopefully it has helped.
:I've read what you've added ... I'll reword a bit about the 15 degree west because it isn't immediately obvious that this is an hour unless you already know the subject! It's really quite a difficult subject to put in a few words. It really needs a few people to read it and see if it makes sense!
Mike 11:48, 8 February 2007 (UTC)
replies: text: PS. I've remembered why I came here - it was to do with the error - having worked out the rough error I put in that section, which I thought would be useful, but I'm not too concerned if it disappears!Mike 12:11, 8 February 2007 (UTC)
thread_title: Untitled

message: PPS. Thanks for the article, I remember a TV program on "Longitude", where it simple asked the audience to laugh at another approach to working out position. Now that I understand the technique it explains not only what the other approach was, but a lot of history such as why they built observatories on remote islands - it was to create a realiable and accurate local fixed reference point from which they could then work out the exact position of other local points using much less accurate equipment so long as it was calibrated to the known reference point!
I presume that is also why they were so interested in solar eclipses. I assume they could calculate the time of the eclipse much more accurately than their time pieces could measure time, therefore using an eclipse, they would have a very accurate local time reference from which, using the moon's position they could then very accurately determine the longitude of the observatory .... it all makes sense because of this article! Mike 12:11, 8 February 2007 (UTC)
thread_title:  Additions to article (was thanks) 

message: Using the method of lunar distances to find longitude and time is tricky business.
There are a lot of corrections applied to get the required accuracy.
Here are some of the esoterica:
* The sun very rarely reaches its highest point exactly at noon.  "Local apparant noon" is the time when the sun passes the observer's meridian.  Because the sun's declination is always changing, the sun will reach its highest point just before or just after this time.  Only at the precise moment of solstice does the sun's declination "pause".  Near the times of the equinoxes, the difference between the time of the sun's maximum height and its crossing of the meridian is greatest (perhaps as much as 40 to 50 seconds).  Thanks to GH for reminding us of this one.  --SV Resolution(Talk) 16:47, 25 July 2007 (UTC)
thread_title:  Esoterica 

message: In my updates to this page, I am relying on the expertise of several individuals knowledgeable in the current (yes, current!) and historical practice of using lunar distances for longitude.  I expect a lot (for this article) of activity in the next month or so, and hope to get all the facts properly cited. --SV Resolution(Talk) 12:33, 31 July 2007 (UTC)
thread_title:  Sources of information 

message: When exactly did HMNAO stop publishing the lunars?  1852 or 1906?
http://www.math.uu.nl/people/wepster/ldtab.html says that radio signals were used for setting chronometers at sea by 1905, the last year the HMNAO published lunars. --SV Resolution(Talk) 04:36, 3 August 2007 (UTC)
thread_title:  The era of longitude by Lunars 

message: For correcting the dates of the Norie references.  I cannot believe I didn't spot that mistake.  --SV Resolution(Talk) 18:10, 6 August 2007 (UTC)
thread_title:  Thank you, anonymous editor 

message: In the method section, The passage which used to read (152803345):
Knowing Greenwich time and local time, 
the navigator can work out longitude.<ref name="Norie 1828 pg 222"/> 
now reads (153036652):

Knowing Greenwich time and the altitudes of the moon and the other body, 
the navigator can apply the [[intercept method]] to find his latitude and longitude. 
Alternately, the navigator can [[longitude by chronometer|first determine local time, 
and then longitude]].<ref name="Norie 1828 pg 222"/> 

Note the reference to longitude by chronometer.  If you've got the chronometer, why bother with lunars?
As has been noted in the Google NavList group, the intercept method was not used during the "golden age of lunars".
Further, the almanacs originally only gave the moon's GHA and dec at noon and midnight, GMT, so the moon could not originally have been used in the intercept method, in any case. (I do hope the experts at NavList can provide helpful references for this information, so we can include it in the article).
I propose going back to the simpler statement, in order to avoid having to explain that, in the age before chronometers, navigators actually didn't do it that way.
I think that, in the history section, it would be appropriate to list the different approaches taken at different times.  Up to and including the present, of course.  I don't feel qualified to write this history myself, but I do feel strongly that the confusing statement in Method ought to be undone.
--SV Resolution(Talk) 00:53, 23 August 2007 (UTC)
thread_title:  Method 

message: The diagram appears to show the constellation Orion (vaguely), but the Moon cannot be in that position relative to Orion. Setting that aside, since the resemblance to Orion is rather weak, you'll notice that the Moon is a crescent. That means that the Sun would be in the sky to the right of the Moon in a direction perpendicular to the points on the end of the crescent. That would be above the horizon as the diagram is drawn. In other words, the Moon can only appear as a crescent in that orientation in daytime and so the stars would be invisible. Other than that, it's a nice artistic rendering. I like the boat!24.136.6.69 02:56, 4 September 2007 (UTC)
replies: text: I've replaced the image with one that has a more realistic star field.  The distance is shown relative to Regulus in Leo.  I should have rotated the star field clockwise a bit, but didn't notice the problem until nearly done.  At least the relative positions of Regulus and the Moon are realistic. --Michael Daly (talk) 20:54, 10 December 2007 (UTC)
thread_title:  The Diagram 

message: In the first sentence of the Errors section, someone wants a citation for the statement that a lunar distance changes about 1/2 degree per hour. Is that really necessary? It's well known that the Moon makes an orbit in about 30 days. That's 12 degrees per day, or 1/2 degree per hour. I don't think a citation is necessary. Paul Hirose 23:50, 15 September 2007 (UTC)
replies: text: It just repeats what is written in the previous section (which is referenced), so I just added the same reference in the Errors section.  Michael Daly 05:53, 13 October 2007 (UTC)
thread_title:  Lunar rate needs citation? 

message: Note that there was some significant additional discussion leading to edits of this Wikipedia page on the Navigation List (traditional navigation discussion group). Most of the direct discussion took place in August, 2007. Visit the group's archive  and search on Wikipedia. There are also numerous discussions of lunar distances generally in this archive. Membership is open to anyone. 24.136.6.69 22:52, 22 October 2007 (UTC)
thread_title:  Additional discussion 

message: I think the subject of how to 1) determine local time and 2) how to get from local time vs. GMT to longitude should be discussed more explicitly.  Determining local time might warrant its own entry.--icedtea1954 (talk) 01:26, 23 January 2008 (UTC)
thread_title:  Need more discussion on determining/using local time 

message: When computing the difference between GMT and local time, one has to take the Equation of time into account. It amounts up to a quarter of an hour! Rgds --Boobarkee (talk) 12:39, 18 August 2009 (UTC)
thread_title:  [[Equation of time]] 

message: I`m in search for data on the accuracy of astronomic derived longitude (land based, I assume lunar eclipse or occulation) before the time of telescopes and marine dead reckoning accuracy (all times, all ships) -- Portolanero (talk) 14:36, 16 June 2011 (UTC)
thread_title:  Longitude before the Telescope 

message: In Practice
...
Step One – Preliminaries
    ... other body (see any nautical almanac from 1767 to c.1900).[citation needed]
To my way of thinking, 'see any nautical almanac' is all the citation needed, considering that a number of them are available. That fact ought to be known to most readers of this article.
97.112.224.68 (talk) 19:55, 30 September 2012 (UTC)
replies: text: I agree these are questionable requests for citation.  However, I've added one for the second, specifically referring to an example of corrections for lunar semidiameter given in Dutton's.  Adding a citation for a source that is rather old (i.e. for the first item) is a bit more of a challenge.99.245.230.104 (talk) 09:00, 23 June 2014 (UTC)
thread_title:  Is 'citation needed' really needed? IN PRACTICE section 

message: I read somewhere that the cost of sextants could exceed the cost of chronometers, and if I find it again, will post the reference here. --Pawyilee (talk) 10:28, 7 December 2012 (UTC)
thread_title:  Relative costs 

message: This little anecdote is interesting to some, but provides nothing of significance to the topic of the lunar distance method.  Can someone suggest a valid reason for its inclusion (as opposed to any number of other anecdotes about lunars)? 99.245.230.104 (talk) 08:57, 23 June 2014 (UTC)
thread_title:  What is the USS Peacock section for? 

message: I've removed mention of it for the time being since it was uncited, unmentioned by Britannica, and centuries off the first use listed here, but William Baffin's page formerly claimed he had practiced lunar distance. Kindly restore it with citation there and add it here if that's an accurate claim. Worth noting the error if it turns out to have been one. — LlywelynII 12:57, 4 December 2015 (UTC)
thread_title: William Baffin

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thread_title:  External links modified 

message: The article mentions Greenwich mean time 18 times, out of which 15 are not titles of references or links to Greenwich-specific entities. So as I think that the English are not the only ocean-faring people, lunar reckoning was done also before the adoption of GMT as the international standard time (actually primarily so), and I further do not think that "Greenwich" is widely used as a synonym for "national standard meridian", I would suggest to change the relevant instances to "reference time". Note that the question whether the English Wikipedia is to be seen as the Wikipedia of the English-speaking peoples or rather as the main international Wikipedia does not apply here, as probably also for British subjects the way how other nations calculated their longitude is relevant (and even then there would also be the US-Americans, or did they, and the Spanish, Dutch and French, really use almanacs with reference to GMT?). Seattle Jörg (talk) 06:51, 22 October 2018 (UTC)
thread_title:  Not specific to GMT 

message: Following this post by Frank Reed on NavList (http://fer3.com/arc/m2.aspx/Navigation-articles-Wikipedia-FrankReed-aug-2019-g45682), and the recent workshop on Lunars at Mystic Seaport I suggest we have an improvement drive for this article. Billlion (talk) 22:21, 28 August 2019 (UTC)
thread_title:  Improvement drive