Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site cbosgd.UUCP Path: utzoo!linus!decvax!harpo!eagle!mh3bs!mhtsa!exodus!gamma!ulysses!mhuxl!ihnp4!cbosgd!djb From: djb@cbosgd.UUCP Newsgroups: net.astro Subject: Halley's Comet Message-ID: <1020@cbosgd.UUCP> Date: Sat, 25-Feb-84 23:35:14 EST Article-I.D.: cbosgd.1020 Posted: Sat Feb 25 23:35:14 1984 Date-Received: Sun, 26-Feb-84 23:17:49 EST Distribution: net Organization: AT&T Bell Laboratories, Columbus Lines: 70 I just recently received my copy of the "International Halley Watch Amateur Observers' Manual for Scientific Comet Studies" (by Stephen J. Edberg) and am quite pleased. It is a treasure trove of information on comet watching in general, and on Halley's Comet and its 1986 appearance. The first part of the book is on methods, including information on visual, photographic, astrometric, spectroscopic and photometric studies. The second half contains a day-by-day ephemeris from 6/4/1985 through 5/4/1987, and a sequence of 19 specially modified AAVSO star charts that show Halley's position in the sky from Nov. 1985 through May 1986. In addition, there is a section that describes the International Halley Watch, an organization that will allow amateur astronomers to network together and particpate significantly in the study of Halley's Comet. Forms are included that allow you to register yourself as a member of the network, and also for recording and reporting your observations. A quick pass through the book is enough to convince you of the great discrepancy between the appearance for northern hemisphere observers and for those in the southern hemisphere. For example: Date Dark Hours vs. Observers Latitude Magnitude* (1986) 45 N. 30 N. 30 S. 45 S. ------------------------------------------------------------- (* Recent study Mar. 7 0.2 0.9 2.0 2.0 4.5 (indicates that 17 0.5 1.5 3.3 3.7 4.5 (Halley's may be 27 0.7 2.3 5.3 6.2 4.3 (as much as two Apr. 6 0 3.8 9.1 9.4 4.0 (magnitudes 16 6.0 8.3 10.0 9.9 4.4 (brighter than 26 6.2 8.0 9.2 10.0 5.5 (these values! ------------------------------------------------------------- Dark hours are the interval during which the Sun is below the local horizon by at least 18 degrees and the comet is simultaneously visible above the local horizon. Notice the difference between the values for observers at northern latitudes and those at southern latitudes. As you would expect from the above table, the altitude of the comet is similarly much better for southern observers: Date Comet Altitude vs. Observers Latitude (1986) 40 N. 30 N. 20 N. 20 S. 30 S. ------------------------------------------------------ March 6 5 10 15 22 22 16 8 15 24 40 40 26 10 20 30 59 60 April 5 6 15 27 65 73 10 - 10 15 49 55 ------------------------------------------------------ Altitude is given in degrees at the beginning of morning astronomical twilight. I highly recommend this book to anyone planning to take more than casual notice of Halley's Comet. It does assume some rudimentary astronomical knowledge, but encourages any amateur observer to particpate in the Halley's Watch network, regardless of skill level or equipment. Dedication and patience are all that is required. If you are interested, the book is available through Sky Publishing (check any recent issue of Sky & Telescope for ordering info). Me, I'm taking March 1986 off and heading for Australia or New Zealand. * * David Bryant AT&T Bell Laboratories * Columbus, OH 43213 * (614) 860-4516 * . . djb@cbosgd.UUCP cbosgd!djb@Berkeley.ARPA * *