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Occdhtlm3newstelter OccdhtlM3Newstelter Volume II, Number 10 january, 1981 Occultation Newsletter is published by the International Occultation Timing Association. Editor and Compositor: H. F. DaBo11; 6 N 106 White Oak Lane; St. Charles, IL 60174; U.S.A. Please send editorial matters to the above, but send address changes, requests, matters of circulation, and other IOTA business to IOTA; P.0. Box 596; Tinley Park; IL 60477; U.S.A. NOTICE TO LUNAR OCCULTATION OBSERVERS paho1. by contacting Sr. Francisco Diego Q., Ixpan- tenco 26-bis, Real dc Ids Reyes, Coyoacdn, Mexico, L. V. Morrison D.F., Mexico. Currently, however, the Latin American Section is experiencing problems with funding, and On 1981 January 1 the international centre for the for the time being, it may be necessary for would-be receipt of timings of occultations of stars by the IOTA/LAS members to subscribe to the English-lan- Moon will be transferred from HM Nautical Almanac guage edition of o.n., or to join the parent IOTA. Office, Royal Greenwich Observatory, England to As- tronomical Division, Hydrographic Department, Japan IOTA NEWS "' From that date observers should send their lunar oc- cultation reports and any correspondence connected David W. Dunham with lunar occultations to the following address: As of 1981 January 1, H. M. Nautical Almanac Office, Astronomical Division at the Royal Greenwich Observatory, England, will Hydrographic Department discontinue collecting observations of lunar occul- Tsukiji-5 tations. After that date, observers should send Chuo-ku, Tokyo their reports to the new International Occultation 104 JAPAN Centre in japan, as described in this issue's lead article. This poses a problem for 1980 reports, The layout of the report form may be changed a lit since most observers have been filling out their tie and observers should write to the Hydrographic HMNAO occu1tation report forms as they make their Department for new forms. During this change-over observations, and new report forms have been de- period it is important that observers should give signed by the I.O.C. Any reports sent to HMNAO will their full postal address, positions and descrip- simply be sent on to Japan. Since the I.O.C. report tions of their telescopes on the report forms, oth forms are rather similar to HMNAO'S, the I.O.C. erwise there may be considerable delay in reducing might accept reports, for 1980 only, on HMNAO's their observations. forms. I have written to the I.O.C. asking if this is all right, and hope to publish their reply in the Observations of occultations of stars by planets, next issue, which we hope to distribute early in satellites or minor planets should continue to be February. In the meantime, you might hold onto your sent to HM Nautical Almanac Office. 1980 data until we publish the decision. Also, the new I.O.C. report forms should be available by then, FROM THE PUBLISHER so that if you have not already filled out an HMNAO form, you could use the new forms instead. In any <~ For subscription purposes, this is the fourth and case, start using I.O.C. forms as soon as possible. final issue of 1980. Guillermo MallCn reports continued difficulties with O.n.'s price is $1/issue, or $4/year (4 issues) in high demand for use of the computer at the Universi- eluding first class surface mailing, and air mail "... dad Naciona1 Autonoma dc Mexico, so that graze pre- Mexico. Air mail is extra outside the U.S.A., Can."- dictions for Latin American section members are da, and Mexico: $1.20/year in the Americas as far still available only through membership in the main south as Colombia; $1.68/year elsewhere. Back is- I.O.T.A. Ma11Cn is applying for resumed support of sues also are priced at $1/issue. Please see the IOTA/LAS operations in Mexico City, hoping for com- masthead for the correct ordering address. puter access perhaps in April, hopefully in time to compute graze predictions for the second half of IOTA membership, subscription included, is $7/year 1981. If you need the total occultation predictions for residents of North America (including Mexico) for 1981 which were originally supplied by Mdllen, and $9/year for others, to cover costs of overseas write to me at P. 0. Box 488, Silver Spring, Mary- air mail. European (ordinarily excluding Spain and land 20907, U.S.A. If there is a large demand for Portugal) and U. K. observers should join IOTA/ES, such predictions, I will send magnetic tape data for sending DM 12.-- to Hans j. Bode, Bartold-knaust Latin America to Walter Morgan so that he can supply Str. 8, 3000 Hannover 91, German Federal Republic. them. Spanish, Portuguese, and Latin American occultation observers ordinarily may have free membership in The American Ephemeris and Nautical Almanac has been IOTA/LAS, including Occultation Newsletter en Es- substantially revised for 1981, and renamed The 174 Astronomical Almanac, published jointly by the Royal The inclusion of K-catalog stars in the regular USNO Greenwich and U. S. Naval Observatories. There is total occultation predictions for 1981 was mentioned an error in the 198] edition: The ephemerides given in the last issue. The calculation of J-catalog for the four main minor planets are 1abe11ed as predictions for 1981 will be delayed until February, "astrometric, 1950" when in fact they are apparent to allow time to create a new catalog with Praesepe- of date. Starting with the 1982 edition, these cluster stars, more southern stars from the Southern ephemerides actually will be astrometric, 1950. Astrographic Catalog project, and more northerly stars in the northern Milky Way from the Astrogra- The errors in USNO'S XZ catalog, described in o.n. 2 phic Catalog. These stars are not in the current J- (6) 58-60, have still not been corrected. Hence, catalog, but begin to be occulted during 1982 as the the magnitude of X05404 is still given as 5.8 in the Lunar node regresses. The delays in doing this work USNO total occultation predictions for 1981, al- have resulted from the usual new-year prediction though the star's magnitude is actually 11.3. Thom- crunch, greater this time due to the much larger as Van Flandern has recently programmed a method for number of planetary occultations during 1981, and my updating information about non-SAO stars in the XZ involvement with favorable but time-consuming aster- catalog. Sometime during the next few months, I oidal occultation observations late in 1980. plan to write a program to read my magnetic tape of K - XZ matched data and generate input data to cor- John Phelps produced and distributed the very useful rect the bad magnitudes and spectral types in the IOTA membership list of 1980 September. I found current version of the XZ. So if X05404 is occulted only a few errors, such as "Chris Aikhan" (should be during ]982, its magnitude should be listed correct- "Chris Aikman"). Dr. A. a. Nefedjev, who computed ly as ]1.3 in the USNO predictions for that year. graze predictions for Soviet observers, died a few years ago. Just after the list was produced, Our first publication on Solar variations from Richard Nolthenius moved to 1137 N. Clark, Apt. 5, eclipses, "Observations of a Probable Change in the still in West Hollywood, CA, and Derald Nye moved to Solar Radius Between 1715 and 1979," has appeared Route 7, Box 511, Tucson, AZ 85706. The geographic- in Science 210 (4475) 1243-1245, issue of 1980 De- al listing in Part II should be most useful for con- cember 12. We have not yet received reprints, but tacting other observers in your area. a large supply should be available soon, hopefiillt to be announced in the next issue of o.n. Copies Byron D. Groves, 601 N. Parkcenter Dr., Suite 10], will be sent to a]] observers who reported observe- Santa Ana, CA 92705, wrote to me in September asking tions, or otherwise were involved in the effort, again if I.O.T.A. would like to meet with the West- near the edges of the 1976 and 1979 total eclipse ern Amatetir Astronomers in Orange, CA, from 1981 paths. More recent analyses were mentioned on p. July 23 to 26, and assumed that we would not if he 102 of the last issue, but further more refined had no reply by Thanksgiving. I had hoped that this calculations have shown no significant variation issue would ha:ie been distributed before then, to between the total eclipses of )979 and 1980, but see if there was any interest in at least a regional perhaps a small expansion from 1976 to ]979. J.H. IOTA meeting. I did not reply, since the dates con- Parkinson, L.V. Morrison, and F.R. Stephenson haw flict with a possible trip to observe the 1981 July published an analysis of central eclipse timings 1· 31 Solar eclipse, and the distance is too great for a paper, "The Constancy of the Solar Diameter ovej the other IOTA officers. If there is some local in- the Last 250 Years," in a recent issue of Nature. terest, an at least informal regional IOTA session They found no significant variation, but their ob- might still be arranged. servational errors are greater than ours since their method does not have the advantage of the Last August 12th, Russ Genet, M. D. Overbeek, Wayne grazing geometry and is much more strongly affecttm Warren, Hark Trueblood, and I met in Silver Spring, by random and 1ibration-dependent systematic errot- MD, to discuss photometry of occultations.
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