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THE ROYAL ASTRONOMICAL SOCIETY OF CANADA Standing Committee On Observational Activities Programme for Solar Eclipse of Ju]y 20, 1963 ______________________________________________ Bulletin No. 7 June 10, 1963 SPECIAL PROJECTS Since the National Eclipse Committee began issuing this series of bulletins as a guide for those who intend to observe the forthcoming solar eclipse, a number individuals have written describing more advanced or specialized projects which the intend to carty out. In addition, it was realized while the other bulletins were being prepared that certain of the programmes described should receive more elaborate treatment than was then possible. The purpose of this bulletin is to provide a more detailed description of some aspects of the proposed observation programme. The list of projects herein is probably not complete. Hence we would be interested to hear of arv other special projects which are being contemplated. If arwone still firS the information in this bulletin inadequate, he is invited to write to the co-ordinator for further information. 1. The Committee would like to draw attention to the directions in Bulletin No.3 for observing the flash spectrum with a diffraction grating and binoculars or a tele- scope. Transmission gratings aflai most of the incident light to pass through in a "white" beam. This beam must be avoided as it will injure the eye. The spectrum emerges fran the grating at a fairly wide angle to this beam, and this angle can be best found experimentally by placing the grating over the objective and projecting the image onto a white card. When the spectrum emerges straight cut behind the eyepiece, the white beam should not be visible at all. For maximum safety the instrument should be mounted so that it will not accidentally be aimed at the sun when the observer looks in. 2. Since Bulletin No.4 was published, Kodak has issued a revised booklet on solar eclipse photograjfty. Although substantially the same in most respects as the Original edition, it contains the following points which are worth mentioning: (1) Neutral density PHOTOGRAPHIC filters are not suitable for visual use, since they transmit infrared rays which can burn the eye. (2) When preparing to photograph the corona, bear in mind that Kodachrome II has a speed of ASA 25, raised from 10, and Tri-X pan film is now rated at 400 instead of 200. (3) The following section of the exposure table needs to be revised as noted: FILM INNER CORONA OUTER CORONA old new old new Tri-X f/8 @ 1/10 f/16 @ 1/10 f/8 @ 1/2 f/16 @ 1/2 Roy. Pan " f/11 @ 1/10 " f/11 @ 1/2 High Speed Ektach. " " " "