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Subject: SPACE Digest V13 #415

SPACE Digest                                     Volume 13 : Issue 415

Today's Topics:
          Electronic Journal of the ASA - April 1991

Administrivia:

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Date: 16 Apr 91 19:45:08 GMT
From: deccrl!news.crl.dec.com!shlump.nac.dec.com!advax.enet.dec.com![e-mail]  (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.

         [e-mail]

         ASA BBS: [phone], 300/1200 Baud.

        or telephone the Society recording at [phone] 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:

        [e-mail]
        or - ...!decwrl!advax.enet.dec.com!klaes
        or - [e-mail]
        or - [e-mail]

        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

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End of SPACE Digest V13 #415
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