On the new method of determining the longitude by the culmination of the moon and stars being a paper read before the Astronomical society of London. To which are now added an appendix, and a list of stars, applicable to the purpose, for the year 1825 / By Francis Baily.

  • Francis Baily
Date:
1824
Catalogue details

Licence: Public Domain Mark

Credit: On the new method of determining the longitude by the culmination of the moon and stars being a paper read before the Astronomical society of London. To which are now added an appendix, and a list of stars, applicable to the purpose, for the year 1825 / By Francis Baily. Source: Wellcome Collection.

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    very small, as between Altona and Gottingen, or between Greenwich and Paris: nor where it amounts to several hours, as between observatories situated in dif¬ ferent hemispheres. It is true that the horary motion may be safely employed when the difference of longitudes is nearly one hour, or even when it extends to two or three hours (which will comprise the greater part of the observa¬ tories in Europe): but in every other instance, it is evident that an incor¬ rect allowance is, in such case, made for the second differences in the moon’s motion during the given interval. And it happens that the error, occasioned by this assumption, is the greatest about the time of the full moon, when comparisons of this kind are most frequent. As nothing therefore is gained by such an assumption, it will be better in all cases to adopt the true interval (to the nearest minute), and compute the true difference in the moon’s right- ascension for that period; in the manner already proposed in this paper. I would remark, however, for the information of those who wish to retain the mode of solution by means of the moon’s horary motion, that MM. Bessel, Hansen, Nicolai, and Mollweide have, in Nos. 33, 37, and 40 of M. Schumacher’s Astron. Nach., given various formulae and tables for de¬ termining such horary motion ; which will be found very useful and con¬ venient to those who choose to retain this mode of computation. 25. 1 shall now give another example of the application of the formulae above mentioned. On May 30, 1822, M. Nicolai observed the difference of time between the culmination of the first border of the moon, and the culmination of a Virginis at Manheim. The difference was likewise ob¬ served at Paris, by M. Bouvard : and on the following day (according to the civil reckoning) by M. Rumker at Paramatta, in New South Wales*. This latter circumstance will not prevent us from connecting the three ob¬ servations together: since we have only to assume Paramatta as the most westerly position, in comparing it with the observatory at Paris ; and then take the complement of the resulting value, for its eastern longitude. The differences observed were as follow, viz. Manheim. Paris. Paramatta. — 33m 7s,74 32m 21s,86 — 5m 41s,81 I shall first deduce the difference of meridians between Manheim and Paris : for this purpose we have t — — 32m 21s,86, and r = — 33m 7S,74; whence (t — r) = + 45s,88. The apparent time of the moon’s culmination at Paris * See Schumacher’s Astron. Nach. No. 29, 42, and 52.
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