267 lines
16 KiB
Plaintext
267 lines
16 KiB
Plaintext
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T H E M A R T I A N C H R O N I C L E
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March 1990 (Edited by J.D. Beish for ASTROFORUM) No. 1
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Mars is back! Throughout 1990 the Red Planet will become more prominent in
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the morning sky until it reaches opposition on November 27. Although Mars'
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apparent diameter will not be as great as it was in 1988, it will still be
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a most respectable 18.1 arc-seconds, permitting high resolution photography
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and quality visual observations of surface features, clouds, and the South
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Polar Cap (SPC). The planet will be very favorably placed in the sky for
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northern hemisphere observers, remaining north of the celestial equator
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between mid-June, 1990 and September, 1991 and attaining a declination of
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+22 degrees during the 60-day period around opposition.
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Practically speaking,the apparition will commence on April 7, when Mars
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attains an apparent disk diameter of 6 arc-sec, allowing quality telescopic
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observations. However, A.L.P.O.'s International Mars Patrol (IMP) astronomers
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are encouraged to make observations even when the planet appears smaller.
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While little or no fine detail can be discerned when the planet is low and of
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small apparent size, gross features, such as Syrtis Major, can be seen. If the
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observer has been regularly recognizing such features and suddenly notes their
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disappearance, one is led to suspect an obscuration, such as a dust storm. In
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the past, such sightings made independently by several observers have shed new
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light on the history of Martian dust storms, even when the planet subtended an
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angle of less than 6 arc-seconds. A red (Wratten 25 or equivalent) filter is
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strongly recommended since it improves image contrast and reduces the apparent
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seeing effects, since red wavelengths are refracted less.
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MARTIAN SEASONS
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During most of the 1990-91 apparition Mars' South Pole will be tilted earth-
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ward with most of Southern Hemisphere spring and all of summer and part of
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southern autumn being observable. Thus astronomers can again study the regress-
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ion of the SPC and follow both Martian antarctic and arctic meteorology. This
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apparition should also allow careful scrutiny of the summer SPC remnant. As
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Mars will have an apparent diameter of over 13 arcseconds at southern autumnal
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equinox (Jan. 5, 1991), there will be an excellent opportunity to determine
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whether the remnant disappears completely or, as was the case in 1988-89, it
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remains throughout southern summer.
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IMP astronomers will have an unusual opportunity in early 1991 to watch for
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the possible reformation of the SPC. During early Martian southern autumn
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(January to April TD) the planet's apparent size will remain respectable and
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its south pole will be tilted earthward, permitting detailed study of antarc-
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tic regions. Does the South Cap expand during this period, or are its secrets
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hidden beneath the south polar hood? In fact, does a hood actually form, or
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are hoods phenomena restricted to the North? We hope that the IMP can provide
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some answers to these questions in 1991.
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SURFACE FEATURES
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Several regions have displayed long-term, or secular, changes in recent years
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and should be monitored closely during the 1990-91 apparition. These include
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Solis Lacus (85W, 28S), Daedalia-Claritas (115W, 30S), Phasis (109W, 30S),
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eastern Sirenum M. (145W, 35S), southern Memnonia and Zephyria, Trivium
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Charontis (198W, 20N), Cerberus II (212W, 10N) and III (240W, 18S), Elysium
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(215W, 80N), Hyblaeus (230W, 30N), Nilosyrtis, and Syrtis Major. In addition
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the Libya-Isidis (275W, 10N) area should be scrutinized to see whether Nodus
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Laocoontis (246W, 20N) and Thoth-Nepenthes (265W, 15N) are still markedly
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faded.
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DUST STORMS -- A REVISED VIEW
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Mars will reach perihelion on June 29, 1990, at which time it will have a
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respectable apparent diameter of 7.8 arc-seconds. Classically, perihelion
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passage, which occurs in late southern spring, heralds a period when global
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dust storms occur. Martian dust storms have been the subject of much media-
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hupe recently, but in point of fact there have been only five well-document-
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ed GLOBAL dust storms on the Red Planet: in 1956, 1971, 1973, and 1977 (two).
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Furthermore, the concept of a true "dust storm season" on Mars is now open to
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question: it may well be that dust clouds can occur at any season on Mars.
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However, Beish's comprehensive analysis of IMP data reveals that there is
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increased probability of seeing dust storms soon after the planet's perihe-
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lion passage, with a second peak occurring in mid southern summer. Thus the
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1990-91 apparition will present an excellent opportunity for monitoring the
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occurrence (or non-occurrence!) of dust clouds. This is of considerable
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importance for our understanding of Martian climate and meteorology and for
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future space exploration.
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The dust storms of Mars have once again become the subject of much study among
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professional planetary astronomers. However these men and women have neither
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the funding nor manpower for a 24-hour worldwide surveillance of the planet.
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A.L.P.O.'s IMP can provide considerable support in this regard as it did dur-
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ing the 1988 apparition. Thanks to recent developments in communication tech-
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nology, we can now have virtually instantaneous alerts for unusual Martian
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phenomena. When such an event is sighted the observer contacts one of the Mars
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Recorders who then informs the rest of the IMP network. Upon verification the
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appropriate professional astronomers are contacted so that they can conduct
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detailed investigations.
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STORM WARNING. To facilitate communication Beish and Parker will monitor
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Compuserve daily during the apparition. Please send messages to both Parker,
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72317,3157 and Beish, 72317,3306. If you have no access to a modem, Dan
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Troiani has kindly volunteered his phone number: (708) 529-1716. Professor
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Asada, 71701,1534, in Japan is now on the Compuserve network, which provides
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us with virtually instant communication with our friends in the O.A.A. We hope
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that our other observers abroad will be able to avail themselves of this
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service.
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*** DANGER ***
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The one thing that must be avoided in reporting dust storms is a false alarm.
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Our mentors in the professional community take a dim view of wasting consider-
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able time and money on spurious information. Thus, after consultation with
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professionals, we have revised our criteria for Martian dust activity.
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The astute reader will note that nowhere in this chronicle has the adjective
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"yellow" been applied to dust. In the past we have referred to dust storms as
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"yellow clouds" and "yellow dust storms." We feel that this is misleading.
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First, it is virtually impossible to see or even photograph accurate colors on
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Mars without employing very specialized techniques. Traditionally, observers
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have employed yellow filters to better reveal dust clouds. The problem is that
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nearly EVERY light feature on Mars is bright through a yellow filter! In
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November, 1989, we were fortunate to have a professional Mars astronomer spend
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several days in Miami reviewing IMP dust storm data. Under his guidance we have
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revised our definition of dust clouds/storms.
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*** NEW CRITERIA FOR MARTIAN DUST STORMS ***
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1. They must appear bright in red light. Dust clouds can be bright in all spec-
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tral regions, including violet, but if they are not bright in red, they are
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most likely not dust. This means that observing and photographing Mars through
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a red filter is a "must" for IMP astronomers. A Wratten 23A will suffice for
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instruments of 20 cm ( 8 inches) or less in aperture, while a W-25 or even 29
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should be employed with larger instruments.
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Photographing Mars through filters presents problems to the amateur observer
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because exposure times are often prolonged beyond the capabilities of his or
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her drive and the limits of seeing conditions. In such cases observers are
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strongly requested to photograph Mars on color slide film. They can than re-
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photograph them through appropriate filters onto black-and-white film. This
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technique is fully discussed in Parker, et al., Journal of the Association of
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Lunar and Planetary Observers (J.A.L.P.O., Vol. 31, Nos. 9-10, July, 1986,
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and in "Introduction to Observing and Photographing the Solar System." Those
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who are unable to use this technique are encouraged to send the recorders
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quality copies of their slides for analysis. Copies should be made on Kodak
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Slide Copy film 5071 to insure good grain and color balance. Commercial copies
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are suggested for this film. If copies are made at home, we suggest Fujichrome
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CDU film. Following the advice of John Sanford, we have tried this film and
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have found it much easier to use than Kodak 5071. If originals are submitted,
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we cannot guarantee their return. We commend those observers who have regularly
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submitted color filter photographs of Mars during past apparitions. These
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include B. Flach-Wilken (Germany), B. Adcock (Australia), and Japan's T.
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Akutsu, T. Ishibashi, N. Matsumoto, and T. Nakugami.
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2. The sine qua non of Martian yellow clouds is movement with obscuration of
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previously well-defined albedo features. Absence of this criterion disqualif-
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ies a candidate from inclusion under dust clouds.
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3. When these clouds reach heights of several kilometers, we have proposed
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that they may cast shadows that are observable from Earth. There are numer-
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ous reports of anomalous transient dark surface markings appearing near yellow
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clouds, especially when the solar phase angle was reasonably large. Anomalous
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dark markings were in fact seen in conjunction with both 1988 dust storms.
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THE A.L.P.O. MARS SECTION -- 1990
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We wish to take this opportunity to thank the 300 IMP observers who sub-
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mitted over 7,000 drawings, photographs, and micrometer measurements of Mars
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during the 1987-1989 apparition. Such an effort is most gratifying but has re-
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quired some reorganization of the Mars Section. In addition to taking on more
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recorders, we have assigned each recorder to a geographical area. Observers
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should correspond with the recorder in his or her area:
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JEFF BEISH, 9460 Toni Dr., Miami, Fl, 33157
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AL, AR, FL, GA, HA, KY, MS, NC, SC, TN, and VA.
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HARRY CRALLE, 3902 E. 29th St. (J-4), Bryan, Texas, 77802
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AZ, CA, CO, KS, LA, MO, NV, NM, OK, TX, UT, and WY.
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CARLOS HERNANDEZ, 2714 Plaza Dr., Woodbridge, NJ, 07095
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AK, CT, DC, DE, MA, MD, ME, NH, NJ, NY, PA, RI, and VT.
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DON PARKER, 12911 Lerida St., Coral Gables, FL, 33156
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U.S. Territories and Possessions and all areas outside U.S.
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DAN TROIANI, 629 Verona Ct., Schaumberg, IL, 60193
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IA, ID, IL, IN, MI, MN, MT, ND, NE, OH, OR, SD, WA, WI, WV.
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*** GUIDELINES FOR IMP OBSERVERS ***
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1. Observations. Submit these to your appropriate recorder. If you want to be
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assured of their arrival, enclose a stamped, self-addressed postcard with your
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material. This is the cheapest and easiest way. We cannot acknowledge all the
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observations received. Drawings should be made on 42-mm diameter disks, or on
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the standard B.A.A. 2-inch disks. We employ overlay templates for data reduct-
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ion, and other sizes are unacceptable. Photographs should be approximately
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1-inch diameter, so that they can be published properly. However, any photos
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will be welcome! Do not send negatives. We welcome videotapes (VHS or Super
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VHS), but do not send originals. Please edit videos -- no more than 5 minutes
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per observation. We fall asleep easily. Please include date, times.
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2. Observing Forms. Send a stamped, self-addressed envelope (SSAE) to Beish or
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Parker. They will return it with an A.L.P.O. Mars Section observing form en-
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closed from which you can make copies. A copy of Ebisawa's excellent map of
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Mars will also be included upon request.
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All observations must have the observer's name, the U.T. date, the starting
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and ending U.T.'s, and the telescope, magnifications, and filters employed.
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Mark drawings and photos with "South" and "Preceding" so that we know the
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orientation. Other information, such as C.M. and Ls, is not required but is
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appreciated.
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3. Correspondence. All correspondence should contain an enclosed SSAE. Remem-
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ber that the A.L.P.O. staff is volunteer -- both with time and money!
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4. Martian Chronicles. Those who wish to subscribe should send 6-8 SSAE's to
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Beish or Parker. Overseas members cannot send stamps but often send internat-
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ional postal certificates with their envelopes. We wish to thank the many
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observers abroad who did this during the last two apparitions. Their help was
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much appreciated!
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5. A.L.P.O. Membership in A.L.P.O. is not required for the IMP. However, we
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strongly urge our observers to join if for no other reason than they can see
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the fruits of their labor in print in the apparition reports and other papers
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in The Strolling Astronomer. Subscribing to the J.A.L.P.O. also gives one the
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opportunity to read about others' observational techniques and methods of data
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reduction. In addition, the observer may find other fields which stimulate his
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interest, such as observing Pluto. U.S., Canada, and Mexico, send $14 for one
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year or $24 for two years to Harry D. Jamieson, P.O. Box 143, Heber Springs,
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Arkansas, 72543. Other countries: $16 for one year, $29 for two.
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6. Observing Aids.
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a) Mars Observer's Handbook, by J.D. Beish and C.F. Capen. This is being re-
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published by the Institute for Planetary Research Observatories. It is a 55-
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page, copiously illustrated book on Mars observing techniques, including how
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to make drawings and micrometer measurements, tips on photography, use of
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filters, etc. Send $10.00 to Jeffrey D. Beish, 9460 Toni Drive, Miami, Florida
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33157.
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b) The A.L.P.O. Solar System Ephemeris: 1990. This contains the complete
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ephemerides for the Sun, Moon, planets and minor planets as well as selected
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comets. This is a "must" if one is to get full enjoyment from his observing.
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Send $6.00 to A.L.P.O., P.O. Box 16131, San Francisco, CA 94116.
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c) Introduction to Observing and Photographing the Solar System, by T.A.
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Dobbins, D.C. Parker, and C.F. Capen. Contains both theoretical and observat-
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ional information on Solar System objects. Very detailed chapters on Mars,
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astrophotography, micrometry, etc. Forward by A.L.P.O. founder Walter H. Haas.
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Hardcover, $19.95 from Willmann-Bell, Inc., P.O. Box 35025, Richmond, VA
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23235, (804) 320-7016.
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d) IMP Astronomical Calculator (IMPAC). Computer program containing complete
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ephemerides of Mars and Jupiter for any year and geographical location. Also
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rise and set times, altitude, azimuths for all Solar System objects for observ-
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er's location. Automatic correction for Daylight Time, lunar phases for star
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party planning, telescope and mirror cell design, and comprehensive astro-
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photography program. Subroutines for color filter calculations and automatic
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computation of Martian polar cap and Jovian belt latitudes from observer's
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input. For IBM XT, AT and compatibles, monochrome, EGA, or VGA. For a 5.25-
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inch diskette, send $49.95 to J.D. Beish at above address.
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Again, many thanks to the dedicated IMP observers for their excellent work in
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the past. In the past, some observers have not sent in their observations be-
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cause they felt their work inadquate, please send them, especially those color
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photographs -- how many discoveries go undetected............................?
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The Association of Lunar and Planetary Observers -- International Mars Patrol
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Good Seeing in 1990-91!
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Don Parker Jeff Beish Carlos Hernandez
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Harry Cralle Dan Troiani |