Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from hogtown.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Wed, 17 Apr 91 01:50:44 -0400 (EDT) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Wed, 17 Apr 91 01:50:32 -0400 (EDT) Subject: SPACE Digest V13 #415 SPACE Digest Volume 13 : Issue 415 Today's Topics: Electronic Journal of the ASA - April 1991 Administrivia: Submissions to the SPACE Digest/sci.space should be mailed to space+@andrew.cmu.edu. Other mail, esp. [un]subscription requests, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Date: 16 Apr 91 19:45:08 GMT From: deccrl!news.crl.dec.com!shlump.nac.dec.com!advax.enet.dec.com!klaes@decwrl.dec.com (Larry Klaes) Subject: Electronic Journal of the ASA - April 1991 THE ELECTRONIC JOURNAL OF THE ASTRONOMICAL SOCIETY OF THE ATLANTIC Volume 2, Number 9 - April 1991 ########################### TABLE OF CONTENTS ########################### * ASA Membership/Article Submission Information * The Mystery of ZOND 2 - Andrew J. LePage * In Search of the Horsehead Nebula - Eric Greene ########################### ASA MEMBERSHIP INFORMATION The Electronic Journal of the Astronomical Society of the Atlantic (EJASA) is published monthly by the Astronomical Society of the Atlantic, Inc. The ASA is a non-profit organization dedicated to the advancement of amateur and professional astronomy and space exploration, and to the social and educational needs of its members. Membership application is open to all with an interest in astronomy and space exploration. Members receive the ASA Journal (hardcopy sent through U.S. Mail), the Astronomical League's REFLECTOR magazine, and may additionally purchase discount subscriptions to ASTRONOMY, DEEP SKY, SKY & TELESCOPE, and TELESCOPE MAKING magazines. For information on membership, contact the Society at: Astronomical Society of the Atlantic (ASA) c/o Center for High Angular Resolution Astronomy (CHARA) Georgia State University (GSU) Atlanta, Georgia 30303 U.S.A. asa@chara.gsu.edu ASA BBS: (404) 985-0408, 300/1200 Baud. or telephone the Society recording at (404) 264-0451 to leave your address and/or receive the latest Society news. ASA Officers and Council - President - Don Barry Vice President - Nils Turner Secretary - Ken Poshedly Treasurer - Alan Fleming Board of Advisors - Edward Albin, Bill Bagnuolo, Jim Bitsko Council - Jim Bitsko, Bill Crane, Toni Douglas, Eric Greene, Larry Klaes, Tano Scigliano, Bob Vickers, Michael Wiggs, Rob Williams ARTICLE SUBMISSIONS - Article submissions to the EJASA on astronomy and space exploration are most welcome. Please send your on-line articles in ASCII format to Larry Klaes, EJASA Editor, at the following net addresses or the above Society addresses: klaes@advax.enet.dec.com or - ...!decwrl!advax.enet.dec.com!klaes or - klaes%advax.dec@decwrl.enet.dec.com or - klaes%advax.enet.dec.com@uunet.uu.net You may also use the above net addresses for EJASA backissue requests, letters to the editor, and ASA membership information. Please be certain to include either a network or regular mail address where you can be reached, a telephone number, and a brief biographical sketch. DISCLAIMER - Submissions are welcome for consideration. Articles submitted, unless otherwise stated, become the property of the Astronomical Society of the Atlantic, Inc. Though the articles will not be used for profit, they are subject to editing, abridgment, and other changes. Copying or reprinting of the EJASA, in part or in whole, is encouraged, provided clear attribution is made to the Astronomical Society of the Atlantic, the Electronic Journal, and the author(s). This Journal is Copyright (c) 1991 by the Astronomical Society of the Atlantic, Inc. THE MYSTERY OF ZOND 2 Copyright (c) 1991 by Andrew J. LePage The author gives permission to any group or individual wishing to distribute this article, so long as proper credit is given and the article is reproduced in its entirety. Twenty six years ago this month, the unmanned Soviet space probe, ZOND 2, was limping through interplanetary space towards the planet Mars several weeks behind its much smaller American counterpart, MARINER 4. Though launched just two days apart in November of 1964, MARINER 4 - the sole survivor of American's first attempt to reach Mars by spacecraft - followed a much faster trajectory which would bring it past Mars on July 14, 1965. The American craft was destined to become the first space vehicle to flyby the Red Planet and return close-up data. ZOND 2 was scheduled to reach Mars on August 6, 1965, on a relatively slow approach trajectory. Much to the disappointment of the Soviets, ZOND 2 ceased communications enroute to the Red Planet on May 5, 1965, just three months before completing its mission. One major question still remains a quarter of a century after the Soviet probe drifted off into solar orbit: What was the actual mission of ZOND 2? Official Soviet press releases made no mention of its intended mission. Little was said about the experiments and instruments it carried. There have never been any drawings or photographs of the spacecraft released. To this day, ZOND 2 gets little if any mention in Soviet books on the history of spaceflight. ZOND 2 is probably the most mysterious of any planetary mission whose existence has been officially acknowledged by Soviet authorities. What was ZOND 2 suppose to do when it reached Mars? The best place to start is with what we know: ZOND is derived from the French word "sonde", which can be translated as meaning "probe". ZOND 2 was launched by a MOLNIYA booster at 1:12 in the afternoon (Moscow Time) on November 30, 1964. The first three stages of the MOLNIYA placed ZOND 2 and its escape stage into a 153-by-219- kilometer (95-by-136-mile) parking orbit inclined 64.7 degrees to Earth's equator, with a period of 88.2 minutes. Before it completed its first orbit, the Block L escape stage ignited, placing ZOND 2 into a solar orbit with a perihelion of 0.98 AU, an apohelion of 1.52 AU, inclined 6.40 degrees to the ecliptic, and having a 508-day period of revolution. This orbit would bring the spacecraft to the vicinity of Mars after a voyage of 249 days. It would be the longest inter- planetary mission ever attempted up to that time. As a side note, one AU (Astronomical Unit) is the average distance between Earth and the Sun, about 150 million kilometers (93 million miles). ZOND 2, like previous Soviet interplanetary probes, communicated with Earth for a few hours every couple of days to conserve power. The first communication session on December 1 indicated that there was a serious problem. Available power on the spacecraft was only half the expected level, possibly due to a solar panel that did not deploy properly. As a result, any experiments planned for the cruise to Mars were greatly curtailed to save as much electrical power as possible to ensure success for the probe's main goal. The only major experiment announced on ZOND 2 was a new plasma engine to be used in helping the spacecraft orient itself. These plasma engines would first convert a working fluid into a plasma which would then be accelerated by an electromagnetic field to speeds up to one hundred kilometers (sixty miles) per second. These engines may have been included as a possible backup to the main attitude control system. The previous acknowledged Soviet probe to Mars, MARS 1, is believed to have failed in March of 1963 due to a malfunction in its attitude control system. The plasma engines are said to have been tested between December 8 and 18, 1964. ZOND 2 continued on its way to Mars operating at half power. Sometime before February 17, 1965, ZOND 2 most likely made a course correction to fine tune its aim at Mars. After this correction it was determined that ZOND 2 would approach Mars at an angle of 44 degrees to the Sun-Mars line and would be traveling at a speed of 3.77 kilo- meters (2.34 miles) per second relative to the Red Planet when it reached the edge of Mars' gravitational sphere of influence. Calcula- tions indicated that without further corrections, ZOND 2 would pass within 1,500 kilometers (930 miles) of the planet's surface at a peak speed of 5.62 kilometers (3.49 miles) per second. Communications were maintained with ZOND 2 for several months. The spacecraft's communication system began operating irregularly during April of 1965. On May 5, 1965, Soviet technicians were unable to raise ZOND 2. Sometime during the days between communication sessions, the underpowered spacecraft had succumbed to a critical failure, most likely in its communication system. ZOND 2 is believed to have silently flew by Mars on August 6, 1965, and headed off into interplanetary space. These are the only details available on the ZOND 2 mission from Soviet sources. Examining Soviet aerospace engineering practices and other interplanetary missions in the early to mid-1960s, however, does help us begin to fill in some of the blanks in our picture of ZOND 2 and its mission. It has been a Soviet engineering practice since the dawn of the Space Age to use standardized spacecraft as much as possible. As time goes on, existing problems uncovered during ground testing or actual flight are corrected and the reliability and capabilities of the spacecraft are gradually improved. This helps explain the large percentage of failures with the introduction of a new spacecraft. The first few missions invariably uncover hidden problems in the design of the spacecraft. As each problem is discovered and understood, design changes are incorporated into the next version of the spacecraft to correct it. Gradually, spacecraft reliability improves with each successive generation. All VENERA spacecraft launched between 1965 and 1972 as well as ZOND 3 (launched in 1965) and MARS 1 (launched in 1962) shared the same basic design. Indeed, one can easily see the gradual evolution of this design as improvements were introduced making this family of spacecraft more and more reliable over the course of a decade. It is a virtual certainty that all the other unrevealed interplanetary spacecraft launched to Mars in 1962 and 1964, including ZOND 2, and all those launched to Venus between 1962 and 1972 shared this same basic design. Based on an analysis of the evolution of the design of this family of interplanetary spacecraft, we can make a reasonably accurate guess of the design of ZOND 2: The Soviets' first Chief Designer, Sergei Korolov, developed the basic spacecraft design. The detailed design and hardware construction was done by the Babakin Design Bureau and its subcontractors. The spacecraft consisted of two pressurized compartments with a total length of 3.6 meters (12 feet) and a total mass of just under one metric ton, give or take several hundred kilograms. The larger of these two compartments, called the Orbital Compartment, was a cylinder 1.1 meters (3.6 feet) in diameter and about as long. As is the usual Soviet practice, the interior of this compartment was pressurized to about one atmosphere to simulate an Earthlike laboratory environment for its internal equipment. This equipment would have included transmitters, batteries, the astro- orientation and other automated control systems, some experiment electronics, and so on. On top of the Orbital Compartment was a KDU 414 course correction engine developed and built by the Isayev Design Bureau. This engine developed a thrust of 200 kilograms (440 pounds) and used unsymetric dimethylhydrazine and nitric acid as propellants. Also located here was the attitude control system that made use of pressurized gas. Mounted on either side of the Orbital Compartment were two large solar panels that had a total span of about four meters (thirteen feet). These panels supplied electrical power to the spacecraft. The panels were folded against the Orbital Compartment during launch and were deployed after the spacecraft was on its interplanetary trajectory. It is quite likely that one of these panels did not deploy on ZOND 2 thus depriving it of half its electrical power. On the ends of each solar panel were hemispherical radiators which were used to control the interior temperature of the Orbital Compartment. Located on the side of the compartment pointing away from the Sun was a two-meter (6.6 foot) umbrella-like high gain antenna that was used for communications over long distances. Other low gain antennae and in-flight experiments and sensors were mounted on the compartment's exterior. The second pressurized compartment was referred to as the Planetary Compartment. This compartment held instruments that were to be used to examine the target planet. It is this compartment that is the focus of this article. The Planetary Compartments on the MARS 1, ZOND 3, and VENERA 2 spacecraft contained a package of spectrometers and a phototelevision system to analyze the target's composition and take high resolution photographs of the surface. The Planetary Compartments of VENERA 3 through 8 were designed to detach from the rest of the spacecraft and ultimately land on the target planet. While the Soviets never mentioned what type of Planetary Compartment was carried on ZOND 2, indirect evidence suggests that the Soviets were going to attempt a simple landing on Mars over a decade ahead of similar American plans with their VIKING project, originally named VOYAGER and not to be confused with the VOYAGER 1 and 2 spacecraft which explored the Jovian planets from 1979 to 1989. The first piece of evidence comes from Soviet sources: A recent Soviet book about Sergei Korolov, the Soviets' chief spacecraft designer in the early years of the Space Age, titled THE CREATIVE LEGACY OF SERGEI KOROLOV. In this biography, it is stated that a series of spacecraft had been designed by 1964 that would be able to photograph and examine the planets Venus and Mars during flybys and also land on them. The spacecraft descriptions closely match those actual vehicles known to have been launched towards Venus and Mars during the 1960s. It is reasonable to assume that by the time ZOND 2 was launched, the design of a Mars lander existed. In another recent Russian language book, COURSE TO MARS, there is a story about an early Soviet Mars mission. According to this information, an unmanned Mars probe in its final weeks of preparation was found to be overweight for the trip. In order to lighten the spacecraft, Korolov ordered that an experiment designed to detect life on Mars be removed and taken to the barren steppes outside of the Baikonour Cosmodrome for testing. He reasoned that if the experiment could detect signs of life there, it could detect any signs of life on Mars whose surface conditions were expected to be similar. The instrument failed the test and was subsequently omitted from the spacecraft's payload. The only definitive means to detect signs of life is to actually sample Mars' soil or atmosphere. This can only be done by a lander. The conclusion that this experiment was originally on a lander is further supported by the comments that it was taken outside the Cosmodrome, presumably for testing on the ground. Since Korolov was alive for only the 1960, 1962, and 1964 Soviet Mars mission attempts, at least one of these missions (most likely the latter two) must have carried a lander originally capable of performing biological tests on the surface of Mars. Another piece of evidence is the trajectory that ZOND 2 followed to Mars. Most Soviet and American interplanetary probes of that era tried to use the lowest possible Earth departure energy so that the largest possible payload could be carried. At the same time, a trajectory was chosen to minimize the flight time to the assigned planet to increase the chances that the spacecraft would reach its target before it malfunctioned. Also, the trajectory was chosen to minimize the communication distance once the spacecraft reached its target so that greater amounts of data could be transmitted with a smaller transmitter. ZOND 2 seemed to break all these rules. It could have been launched on a lower energy trajectory that would have brought it to Mars more quickly and at a time when Earth was closer to Mars. Instead it was sent into a higher energy trajectory that just happened to minimize its approach speed to Mars. This sort of tactic would only make sense if ZOND 2 was carrying a package that was to land on Mars. A lower approach speed means that the Martian atmosphere would not have to slow the package down as much during entry. This would be important if the Soviets were interested in maximizing the payload delivered to the surface of Mars or increase their safety margin. The idea of a safety margin is very important. The properties of the Martian atmosphere were very uncertain before the flight of ZOND 2 and the American MARINER 4. The general consensus in the early 1960s, when the first Mars landers were designed, was that the Martian atmosphere was composed primarily of nitrogen mixed with a small amount of carbon dioxide. Several reputable astronomers in the 1950s and early 1960s performed measurements which consistently indicated that the Martian atmosphere had a surface pressure of about 80 milli- bars (compared to Earth's 1,013 millibars at sea level), give or take a few tens of millibars. Once again, if we look at typical Soviet aerospace engineering practices, we find that they tend to use simple designs. The simplest construct for a package that must enter a planet's atmosphere is a spheroid whose center of gravity is offset from its geometric center so that one end always points in the direction of travel. This is done so that no sort of active attitude control system would be needed to orient the descending capsule. By the early 1960s, the Soviets were using such a design for their manned VOSTOK and VOSKHOD space- craft as well as Earth spy satellites based on the VOSTOK design. All the VENERA entry capsules starting with VENERA 3 (launched in 1965) used a spherical entry module. The return modules of the Soviet's lunar sample return flights in the 1970s used the same shape. It would be reasonable to assume that the Soviets used a spherical entry module on ZOND 2. I have performed a series of simulations to see if a spherical entry module could slow down enough to actually deploy a parachute and land on Mars. Using the approach data for ZOND 2 and a Martian atmosphere composed primarily of nitrogen with a surface pressure of 80 millibars, I discovered that it was possible for a sphere about one meter (3.3 feet) across weighing less than about 350 kilograms (770 pounds) to easily slow down enough with a fairly large safety margin to take into account the spacecraft's aiming accuracy and the uncer- tainties in the characteristics of the atmosphere. This compares nicely with the entry sphere of VENERA 4, which was one meter in diameter and weighed about 383 kilograms (843 pounds). A Mars lander would weigh much less than this, since it would not have to withstand the higher pressures and temperatures that were expected on Venus. All other things being fixed, the easiest way to increase the safety margin is to minimize the approach speed. If ZOND 2 did carry a lander, what sort of instrumentation would it have carried? As told earlier, it may have been planned to carry some sort of biological package. Although this is purely speculation, it is likely that an early Mars lander would also carry equipment similar to the Soviets' first successful Venus entry probe, VENERA 4, launched in June of 1967. This entry probe carried instruments to measure temperature, atmospheric pressure and density, as well as a simple gas analyzer to estimate the amounts of such gases as nitrogen, oxygen, carbon dioxide, and water vapor. These measurements would begin as soon as the parachute was deployed at an altitude of a few kilometers, and, with some luck, continue to be transmitted directly to Earth for some time after landing. Depending on the weight limita- tions, sensors capable of examining the composition of the soil might also have been carried. Unfortunately, if ZOND 2 did carry a Martian lander, it was destined to fail from the start. Results from MARINER 4 indicated that the Martian atmosphere was much different than expected. Before MARINER 4, Earth-based spectroscopic studies of Mars detected only small amounts of carbon dioxide, amounting to a partial surface gas pressure of a few millibars, but its spectral lines were broadened. The simplest explanation for this was that additional pressure from a gas undetectable by Earth-based spectroscopy, such as nitrogen, was responsible for this broadening. The small amount of detected carbon dioxide accounted for a small fraction of the total atmosphere. An analysis of data returned by MARINER 4 indicated that there was actually little or no nitrogen in the Martian atmosphere and that it was composed mainly of carbon dioxide with a surface pressure of about six millibars. If ZOND 2 had made it to Mars and was carrying a lander designed to pass through the previously assumed dense atmosphere, it would have crashed into the Martian surface at a speed of a few kilo- meters per second, hardly braked at all by the very thin atmosphere! What about the broadened carbon dioxide spectral lines? It was later found to be caused by light scattering off of the dust that permeates Mars' atmosphere. The discovery of the Martian atmosphere's true properties instantly made any Soviet Mars lander design obsolete. A total redesign was now required. What happened next behind the scenes in the Soviet Union is for the most part still unknown. We do know that there were no more attempts to launch a first generation interplanetary probe towards Mars. Not even a photographic flyby was attempted, despite the fact that the hardware was successfully tested on the ZOND 3 mission and could have returned an order of magnitude more photographic data than the simpler MARINER 4. Instead, the Soviets continued to send probes to Venus at every launch window through 1972 in an attempt to learn more about that world's atmosphere and ultimately land on its surface. For whatever reason, the Soviets abandoned all further first generation interplanetary flights to Mars. Whether it was already being planned or decided on as a result of the data returned by MARINER 4, the Soviets began designing a much larger second generation interplanetary probe that would be sent on the PROTON launch vehicle then under development in part to support the Soviets' manned lunar exploration program. This new Mars probe would weigh over four metric tons and be capable of placing a separate newly designed lander on the Martian surface. Depending on how favorable the launch window was, it would even be possible for this new spacecraft to carry enough fuel to slow itself down and enter orbit around Mars. The new lander was designed by a group of relatively young engineers. The lander itself was still spherical in shape but it was placed in a broad conical aerobrake to greatly increase the air drag, thus allowing the package to slow down enough even in the thin Martian atmosphere. High altitude tests of this design were conducted by the Soviets in the late 1960s. It is rumored that the first of these new second generation Mars probes were ready in early 1969. As a result of various factors (and some hindsight), it is generally thought that a couple of these much larger and more capable spacecraft would attempt a repeat of the ZOND 2 mission, this time with a properly designed lander. Two launch attempts around March of that year ended in failure as a result of malfunctions in the unreliable PROTON launch vehicle. Again, at the next Mars launch window in 1971, the Soviets were ready to send their new lander to Mars. The first probe, simply an orbiter without a lander attached to save weight, was launched on May 10, 1971, and became stranded in Earth orbit due to a programming error in the PROTON escape stage's guidance system. The Soviets named this attempt KOSMOS 419 to try and cover the probe's true intentions. Finally, MARS 2 was successfully launched toward Mars on May 19 and was quickly followed by MARS 3 on May 28. History tells us that the MARS 2 lander crashed into the Martian surface on November 27, 1971. The MARS 3 lander, however, did reach the surface in one piece on December 2. Because of problems with the radio relay on the MARS 3 main bus, which had just slipped into orbit around Mars, the lander's signal was lost after only twenty seconds and was never heard from again. After a decade of hard work and a costly false start, Soviet engineers had finally developed the means of delivering a lander through the thin Martian atmosphere to its ruddy surface. The road ahead would be rocky, but in 1971, six years after their first attempt with ZOND 2, they had finally taken the first step towards exploring the Red Planet. For more information on the history of the Soviet Mars program, see Larry Klaes' article, "The Rocky Soviet Road to Mars", in the October 1989 issue of the EJASA. References - Bergaust, Erik, THE RUSSIANS IN SPACE, 1969 Davies, Merton E., and Bruce C. Murray, THE VIEW FROM SPACE, 1971 Gatland, Kenneth, ROBOT EXPLORERS, 1972 Harvey, Brian, RACE INTO SPACE: THE SOVIET SPACE PROGRAM, 1989 Hendrickx, Bart, "Correspondence: Soviet Mars Missions", SPACE- FLIGHT, British Interplanetary Society (BIS), March, 1991 Hess, Seymour L., "Mars as an Astronautical Objective", SPACE SCIENCE AND TECHNOLOGY, Volume 3, 1961 Johnson, Nicholas L., HANDBOOK OF SOVIET LUNAR AND PLANETARY EXPLORATION, 1979 Klaes, Larry, "The Rocky Soviet Road to Mars", SPACEFLIGHT (BIS), August, 1990 Murray, Bruce C., and Merton E. Davies, "A Comparison of U.S. and Soviet Efforts to Explore Mars", SCIENCE, February 25, 1966 Murray, Bruce C., Merton E. Davies, and Phillip K. Eckman, "Planetary Contamination II: Soviet and U.S. Practices and Policies", SCIENCE, March 24, 1967 Wilson, Andrew (Editor), INTERAVIA SPACE DIRECTORY 1989-90, 1989 Wilson, Andrew, (JANE'S) SOLAR SYSTEM LOG, 1987 About the Author - Andrew J. LePage is a member of the Boston Group for the Study of the Soviet Space Program, Krasnaya Orbita. In addition to his interests in astronomical and space related topics, Andrew has been a serious observer of the Soviet space program for over one decade. Andrew is the author of the following EJASA articles: "Mars 1994" - March 1990 "The Great Moon Race: The Soviet Story, Part One" - December 1990 "The Great Moon Race: The Soviet Story, Part Two" - January 1991 IN SEARCH OF THE HORSEHEAD NEBULA by Eric Greene At the December 4, 1990 meeting of the Astronomical Society of the Atlantic (ASA), a group of Society "hard-core" sky observers made plans to visit the Schiffer's observing site at the clear skies near Carnesville, Georgia, on Saturday night, December 5, for an evening of celestial exploration. As darkness fell and the Milky Way burst into full brilliance, a small group made up of the Schiffers, Harry Gelblat and a friend, future ASA members Robert Weaver and Duane Cady and, of course, your humble reporter, started setting up our astronomical instruments. The types of telescopes ranged from Harry's 13.75-centimeter (5.5-inch) Schmidt Newtonian to Duane's brand new Meade 25-centimeter (ten-inch) Schmidt-Cassegrain to Bob's 32.5-centimeter (thirteen-inch) Dobsonian. Rather than spreading across the observing field, the group huddled at one end in the hope that our body heat might ward off the expected chill of the night. The evening started with a magnificent fireball meteor burning across the sky to the west. Little did the observing crew realize, however, that this was just the beginning of one of the best nights yet seen! It was soon noted that while the sky appeared very transparent, seeing was not as good as it might have been. The image of the planet Mars through all the telescopes was very unsteady and very little detail could be seen. However, the transparency soon became a topic of discussion as some of the instruments picked out exceptional detail in the Veil Nebula, a wonderfully bright object in the larger telescopes. While other members of the party spent their time poking around old favorites in the night sky, this observer took advantage of the clear conditions to hunt down a couple of faint galaxies in the con- stellation of Cetus the Whale. While NGC 157 was recorded as bright and easy in the twenty-centimeter (eight-inch) Celestron, nearby NGC 145 was very difficult to view and was best seen with averted vision. Several pleasant hours passed this way while the constellation of Orion the Hunter "rose" higher in the southeast. We were avoiding turning the telescopes on Orion until it was high enough to provide a really spectacular view of the Great Nebula, in an effort to practice some self-control. Around 23:30 (11:30 p.m.) it was decided that the constellation was high enough for a good look. It was soon discovered that the wait had been worth every minute! In the larger telescope, Messier 42 (M42) was magnificent, with the whole nebula showing a hint of color and its streamers taking on the appearance of knotted ropes. As those who have attended the ASA winter observing sessions know, it is usually around this time that I pop up with comments like: "Now, let's see if we can pick out the Horsehead Nebula." The usual response is not fit for publication. For those unfamiliar with the Hunt for the Horsehead, let me describe the usual tactics employed. The Horsehead Nebula (B33) is located just south of Zeta Orionis, also called Alnitak, the eastern- most (leftmost) star in Orion's Belt. The first object to look for is the Flame Nebula (NGC 2024), a large, multipart nebulosity located just to the northeast of Alnitak. Bright Zeta floods the eye with light, making the Flame Nebula a fairly difficult object under most seeing conditions. Placing Alnitak out of the field usually brings a bit of nebulosity into view. Once NGC 2024 is spotted, the telescope is moved a tad south of Zeta to find the nebulous star NGC 2023. Unless both NGC 2023 and 2024 are seen brightly, you can essentially forget seeking the Horsehead. The Horsehead itself is a dark nebula against another very dim bright nebula known as IC 434. Basically, you are looking for a darker area against an almost black sky! Arming Bob's 32.5-centimeter Dobsonian telescope with a fairly wide-field eyepiece and a Lumicon Ultra High Contrast (UHC) filter, the hunt began. Reflection Nebula 2024 was immediately obvious as a very bright nebulosity split with several lanes and easily seen with bright Alnitak in the field of view. Through Duane's 25-centimeter Meade and a moderately high power ocular, the nebula filled my entire field of view. It was one of the best sights of this object I have ever seen! Continuing the stalk, I moved the Dobsonian a bit south of Zeta Orionis to see how NGC 2023 would look. As soon as I put the star out of the field of view, I saw what I thought to be an internal reflection from the eyepiece: A long, fairly bright streak of light. It was not. It was IC 434 jumping out of the field of view as an easily observed band of nebulosity! Silhouetted against this was a large and darker patch. "Holy (expletive)!" I shouted. "I think I see it! Let me check BURNHAM'S to make sure of the field." BURNHAM'S CELESTIAL HANDBOOK (Three volumes, Dover Books, 1978) has several excellent photos of the Horsehead area and we made sure of the placement of the stars that mark the location of this object. Back to the eyepiece I went, and exactly where B33 should be located was seen a dark intrusion into IC 434 - we had the Horsehead! Not only that, but it was a fairly easy celestial object. The seasoned observers were able to hold it easily with direct vision while some of the new observers found the trick of moving the telescope helpful at bringing out the nebula. Flushed with success, we moved to the other telescopes to see what they would show. In Harry's 13.75-centimeter Schmidt Newtonian, the Flame Nebula was quite evident, as was IC 434 both with and without the UHC filter. I thought I could just make out B33, but the short focal length of his telescope and resultant low power made the detec- tion very difficult. Moving to Duane's Meade and the UHC, the nebula was a bit more difficult than in the Dobsonian but still obvious and I was able to pick it up without any filters on the Celestron. Our success was total and, for most of the people present, gave them their first view of this "Holy Grail" of amateur astronomers. As the Moon started to "rise" and the temperature continued to drop, our cold group finally packed away their equipment, being well satisfied with the evening. Although the seeing never did substan- tially improve - it was so bad that splitting the stellar pairs in Epsilon Lyrae was impossible - the night's transparency more than made up for Earth's unstable atmosphere. It was one of those nights that come all too infrequently to most astronomical observers and one that will be long remembered. For more information on the Horsehead Nebula and the constellation Orion, see Michael S. Wiggs' article, "Orion: Winter's Mighty Hunter", in the December 1989 issue of the EJASA. About the Author - Eric Greene, ASA Observing Coordinator, is an active and avid amateur with a talent for astronomical education and an interest in presenting astronomy comprehensively to all levels of interest in the field. Eric is the recipient of the ASA's 1990 Meritorious Service Award for his work as the Society's observing coordinator and for founding and maintaining the ASA electronic bulletin board service (BBS). Eric is the author of the following EJASA articles: "The Cosmic Distance Scale" - April 1990 "Aperture Arrogance" - March 1991 THE ELECTRONIC JOURNAL OF THE ASTRONOMICAL SOCIETY OF THE ATLANTIC April 1991 - Vol. 2, No. 9 Copyright (c) 1991 - ASA ------------------------------ End of SPACE Digest V13 #415 *******************