Talk:Nautical almanac

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Original publication Date[edit]

Wasn't the 1767 issue of the Nautical almanac published in 1766, so as to have been available to mariners during the entire year? --SV Resolution(Talk) 14:24, 31 July 2007 (UTC)

Aries is not a star, and doesn't have an exact location[edit]

Something seems fishy to me about the explanation of Aries being listed in the almanac. When I look at the sample photograph, I see an hour angle specified to very high accuracy, under the column labeled "Aries". But Aries is a constellation, and the entire constellation spans a rather large range of angles, both in right ascension and declination. I suspect that this column is really designating the First Point of Aries, i.e. the position of the ascending node where the ecliptic intersects the equatorial plane. This would be logical because it would correct for time of year for which right ascension is measured. Can anybody verify this? I strongly suspect that this part of the article needs to be corrected. CosineKitty (talk) 15:35, 17 April 2008 (UTC)

Yes, I verify this. The column 'Aries' refers to the first point of Aries and is simply the angular difference between the geographical and the celestial coordinate systems.

Upon further reading, the wording makes it sound like Aries is a star, which is wrong. It is a constellation. CosineKitty (talk) 15:36, 17 April 2008 (UTC)

I agree the current text is in some ways wrong. I also agree, it's not the constellation Aries that is referred to, but the first point of Aries, otherwise known as the equinox, from which the distances of the various stars are measured. There are other problems with the article too, and a few errors: one that I spotted is the reference to extrapolation, which should be interpolation, and much of the text seems to hark back to a stage where the article was about a specific almanac, the UK/US Nautical Almanac. Some of the details given are actually still specific description of that, and would not be generally applicable to almanacs in general. It seems there's now a quite large number of articles about almanacs and ephemerides, and I wonder if the splitting has gone too far? I haven't got time immediately to try and fix this, but will hope to get time to return, it looks like a big job, maybe someone else is interested enough to try ....? Terry0051 (talk) 12:20, 21 February 2009 (UTC)

GHA and SHA[edit]

It would be great if someone could add explanations to the acronyms in the nautical almanac. That 'Dec' stands for declination (and not decimal) etc. I think that GHA stands for 'Greenwitch Hour Angle', but I have no idea what SHA stands for. 130.237.216.122 (talk) 08:45, 15 July 2009 (UTC)