Photographing the Stars.

Samoa Times and South Sea Advertiser, Volume I, Issue 30, 11 May 1889, Page 2

Photographing the Stars.

Admiral Mouches has written to Mr. Russell to say that it has been decided to hold a meeting of the Astro-Photographic Conference on September 15, this year. It will be remembered that at the meeting of the above conference in 1887, several of the lending astronomer of Europe, together with all the astronomers who should take part in the actual work of photograph ing the stars were constituted a permanent committee to decide what portion of the heavens should he allot i'.] to each observatory, to arrange for the measurement of the photos, when taken, to tost all the photgraphic plates to *ee that they are uniform, and generally to decide upon nil the details of the work. The meeting in September next is understood to he preliminary to the important meeting which is to be held in 1890. It appears thai the work of constructing the telescopes is not going on so rapidly as was anticipated ; and'hat it will probably take until the end of 1889 to finish and erect the photo telescope* for the Cape of Good Hope ami other pjnees which are depending upon the opticians to do this work. Several months will then he required for experiments in which each astronomer will find out the. best way of doing the work, also the quality of his instrument, and generally gain experience, after which they will meet to finally decide upon the deiails of the great work. Sir Howard Grubb, of Dublin, has the making of all the object glasses for the photographic telescopes for England and hercolouies, and also of the elaborate mounting or stand required for using them, for all the places except Sydney, and at the present time all the heavy parts of the Sydney stand sue finished, and it hj expected that it will be completed in June next The building is ready, and the piers for supporting the instrumeht have l»een built tor some time. The object glass was finished some three months since, and it is expected that it will be here in June, but the cxpct time is sot known because it has to lie tested with the others }>y the Astronomer Royal before he is sent out. ' It has been decided by the Mr-

manent committee that all the reference star* which are to bo used ' to fix the exact position of each plate, and all the »tars on it, shall be re-ob*arved by all the observatories having first-class transit instruments, so that by combining the results ail errors may be eliminated as far as possible. It is perhaps necessary to explain here that the photo-telascopea are constructed to take pictures of parte of the heavens, and in that part to show perfectly the relative positions of the stars, , but they cannot be made to determine absolutely the position of a star in right ascension and declination ; hence it is necessary to fall back upon the only instrument, astronomers have for thai purpose—viz., the transit instrument, and one or more stars whose places have been so determined will be taken in ench photo, and from them the positions of all the others on that plate will be determined. A copy or this list was sent to Sydney Observatory, with a request that the' stars should be observed for the permatiißiient committee, and this work has been in progress for ooino time, i Soon after the conference in Puns. the Astronomer Royal for England expressed the opinion that it would be possible to make the photo-telc-j scopes with a larger Held, i.e., capable of taking larger pbotogfaplrs than 2deg. x 2dcg. a.* agrcqd at the conference, but the letters recently | received, especially one from Dr. ' Gill, astronomer at the (Jape; state : that this is not likely to be resalised, I and thit the photos will probably i be taken with a measurable area of I 2deg. x 2deg. It is therefore imj probable that the number of pho- ; tograpbs. (50,000) deemed necessary j by the conference at Paris will be • reduced.

Up to the present time sixteen observatories have signified their intention of taking part in this work ; but only fpur of these are in the Southern Hemisphere.. Cape, ' Melbourne, Mt/xico and Sydney. If we had amongst us the fam» spirit which animates some American citizens, such a grand opportunity of handing down their names and works to posterity wonhh bo taken advantage of by some of our wealthy citizens ; and observatories to take a rhare in the heavy work the southern astronomers would be established to help in the photographic chart of the heavens.— Sydney Evening Weic*.