SE Newsletter March 1999

Nautical Almanac E charts

From: Patrick Poitevin ppoitevin@village.uunet.be To: SE Mailing List SOLARECLIPSES@AULA.COM Subject: [SE] Eclipse charts of the Nautical Almanac Date: Thursday, January 28, 1999 11:39 PM

A question from Julien Onderbeke:

The Nautical Almanac does exist since 1767. Since when did they have the solar eclipse charts? How did they look like? Are there copies of the solar eclipse charts available? Best regards, Patrick

From: Bob Morris morris@sce.carleton.ca To: SOLARECLIPSES@AULA.COM Subject: Re: [SE] Eclipse charts of the Nautical Almanac Date: Friday, January 29, 1999 12:52

The earliest I have personally looked at was for the April 17, 1912 ring-total eclipse. There was a second eclipse later that year and both charts were fold-outs such that (as I said in my article in the Ottawa Citizen of April 19, 1998) the almanac practically fell open at the eclipse chart for April 17!

And, the title page of the 1912 almanac states "with two inset eclipse maps".

That is why, as I again suggested in my article, all officers on board Titanic were very aware -- once the April 10 sailing date was announced -- that there would be no evening moon during the voyage. "No moon" was -- according to Officer Lightoller's testimony at the British enquiry -- a major factor in the events that led to the disaster.

(There are two ways one can become aware that a new moon will occur on a certain date: one is to find this out from a calendar or from an entry in on a certain page in an almanac, the second to be presented with -- as was the case in the 1912 NA -- several pages of information *and* a fold-out map stating that a central solar eclipse will occur on a certain date. Since there are many new moons in any given year, the former could be overlooked. The latter simply could not.)

Interestingly, Officer Lightoller (who survived to become a hero at Dunkirk -- his personal yacht was part of the flotilla) was the formal "keeper of the almanacs." Part of his job was to distribute the NA to all on board. This is noted in his biography.

Finally, I was amazed to find that -- in an era where computation was tedious -- the NA was prepared well in advance: the 1912 NA was received in Ottawa at the Dominion Observatory on Feb 14, 1911.

Most amazing is that the division of the DO where the almanac was received was (as noted in the stamp on the title page) the "Computing Office."

Bob Morris

From: Jean Meeus JMeeus@compuserve.com To: INTERNET:SOLARECLIPSES@AULA.COM Subject: [SE] Eclipse charts of the Nautical Almanac Date: Friday, January 29, 1999 8:34 AM

As far as I can remember, solar eclipse charts were already published in the preceding century, in the "Nautical Almanac" as well as in the "American Ephemeris" and in the French "Connaissance des Temps".

Chauvenet, in his famous Manual of Spherical Astronomy (1863, new edition 1891, Dover edition 1960) devotes a whole chapter on the calculation of the vario us lines (limits, central line, etc.) and gives as an example the map for the to tal eclipse of 1860 July 18. So I think it must have been current practice then to include eclipse charts in the great almanacs of that epoch. Somebody at the library of the Uccle Observatory might have a look at those older almanacs. Jean Meeus

From: Peter Nockolds pn@egma.sonnet.co.uk To: SOLARECLIPSES@AULA.COM Subject: Re: [SE] Eclipse charts of the Nautical Almanac Date: Friday, January 29, 1999 3:27 PM

Just about on this subject the painted ceiling of the Royal Naval College at Greenwich, dating from the beginning of the 18th century has a good deal of astronomical content. According to notes prepared by the artist (James Thornhill) it includes a depiction of "the celebrated English SAstronomer, the Reverend Mr Flamsteed, who holds the construction of the Great Eclipse which happened April 22nd 1715." Peter Nockolds