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    freebusha

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    Join date : 2011-05-06

    On the other subject

    Post  freebusha on Fri May 06, 2011 3:51 pm

    On the other subject

    On the other subject to which I alludedthe parallax of the fixed starsit would be doing an injustice to the valuable report of Mr. Main, which, as a beautiful specimen of astronomical history, I hope to see ere long adorning our Transactions, if I were to avail myself more largely of it on this occasion than is absolutely necessary. It has long been understood by astronomers, that the research of parallax ought not to be confined to the largest stars, but that, in order to determine our choice of stars for this research, other prima facie grounds for suspecting a proximity to our system ought to be taken into consideration; such as great proper motion, or, in the case of a double star, great apparent dimensions of the orbits described about each other. In the case of the double star Cygni, both these indications combine to point it out as deserving inquiry. In that of a Centauri they also conspire; for it is well known that this fine double star has MBT Shoes a considerable proper motion: and my own observations prove, that the mutual orbit described by its individuals about each MBT other, is of unusually large angular dimension. The great brilliancy of the star also, and its situation in a region of the heavens in which the MBT Shoes Sale stars, generally speaking, seem to be less remote than in others, all favour the expectation MBT Trainers of a measurable parallax being detected in it: and such Mr. Henderson, from his own observations, assigns to it. I am not about to criticise this result; on the contrary, I am disposed to attribute much weight to his conclusion : but it is only on a very long series of observations of absolute places, affected as they are by instrumental error and uncertainty of refraction, that any conclusion of this kind can rest with security.Bessel has attacked the question in a different way, by measuring at all times of the year the angular distance of the stars composing the double star Cygni from two small stars visible in the same field of view, and within limits adapted to secure micrometrical measurement. The method is unexceptionable, the measurements conducted with consummate skill, and their reduction executed with all possible regard to every thing likely to influence the result.

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