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Subject: SPACE Digest V13 #154

SPACE Digest                                     Volume 13 : Issue 154

Today's Topics:
           Apollo lunar surface photography
              Re: Fire in Space
     Re: Kevlar (was:  Manoeuvring using rope and anchor)
   E. Journal of the Astro. Soc. of the Atlantic, Vol. II, No. VII

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  [e-mail].  Other mail, esp. [un]subscription requests,
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Date: 11 Feb 91 12:40:07 GMT
From: world!ksr![e-mail]  (Chris Jones)
Organization: Kendall Square Research Corp
Subject: Apollo lunar surface photography
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In article <[e-mail]>, henry@zoo (Henry Spencer) writes:
>
>(As a side note, if you're looking at a still photograph from Apollo 11
>on the surface, the astronaut is 99.9% certain to be Aldrin, because
>Armstrong had the camera most of the time.  I believe they've turned
>up one still which is, based on context, Armstrong.)  (It took another
>mission or two before they figured out that it was a good idea to mark
>the spacesuits so you could tell the two astronauts apart easily.)

The first mission with the red "racing stripe" on the commander's helmet was
Apollo 13 (not that it got any use on that flight).  This was done since the
surface video camera on Apollo 12 failed shortly after the astronauts got out
of the LM (it got pointed at the sun, I believe, and was useless from then on).
Looking at the stills after the flight, it couldn't always be determined which
astronaut took the shot and which was in it.  Apollo 11 hadn't had this problem
since the whole EVA was televised, and it was easy to correlate the stills with
the video.

One of my favorite shots from the lunar landings is of the LM lift-off, taken by
a remotely operated camera on the last couple of flights.  The camera was
controlled from the ground, and in order to keep the ascent stage in view, it
was necessary to command the camera to track upwards.  The commands had to be
sent somewhat before liftoff due to the 1.3 second earth-moon signal travel
time.
--
Chris Jones    [e-mail]    {world,uunet,harvard}!ksr!clj

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Date: 12 Feb 91 19:28:31 GMT
From: crash![e-mail]  (Dan Gookin)
Organization: Crash TimeSharing, El Cajon, CA
Subject: Re: Fire in Space
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In <[e-mail]> [e-mail] (Brian Finley) writes:

[the reason behind the fire-burning experiments on the shuttle is]

>The objective of the Solid Surface Combustion Experiment is to determine the
>mechanism of gas-flame spread over solid fuel surfaces in the absence of
>buoyancy-induced or externally imposed gas-phase flow.  Measurements in
>low-gravity environment of flame shape and rate of flame spread will be
>made.  This data will provide insight into relative importance of
>gas-phase momentum generated by vaporization/pyrolysis of the fuel surface
>and the diffusion of gas-phase fuel in controlling fuel/air mixing.
>Temperature measurements of both the fuel surface and the gas phase will
>provide an indication of forward heat conduction in both the solid and the
>vapor phases; it also will provide qualitative information on the radiant
>heat flux to and from the fuel surface.

Funny.  I used the same excuse when I was 12 and my father caught
me torching ants with a WD40-powered flame thrower.  :-)

dang

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From: unmvax!ariel.unm.edu!ghostwheel.unm.edu![e-mail]  (John Prentice)
Organization: University of New Mexico, Albuquerque, NM
Subject: Re: Kevlar (was:  Manoeuvring using rope and anchor)
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> [e-mail] writes:
> Person: Greg Cronau
>
> I don't even want to *think* about the number of G's on the spacecraft
> when that sucker goes taunt. You'd have to make the cable out of something
> resilient so that it would stretch to absorb the initial shock.
> You could make the cable out of a kevlar bungee. Certainly would give a
> new meaning to the concept of a "slingshot" manuever. :-)
>

Kevlar was a bit of a fad in rock climbing a few years ago.  It fell a
bit out of favor however because it can be brittle and does not do well
when repeatedly bent or even when tied in a knot.  Put another way, yes,
it has a high tensile strength in uniaxial tension, but it does not have
as high a shear strength (as I recall from the controversy of few years
ago, maybe someone can speak to this who knows more than I do about it).

One thing about using something like Kevlar for a cable that is going
to have to absorb a shock.  It doesn't stretch all that much, so the
force exerted on the places where it is anchored would be tremendous!
If you have to absorb energy, you want something that will stretch and
dissipate the strain more gradually.  That is why rock climbers use
nylon ropes and not steel cables.  Either will stop you, but the steel
cable would cut you in two.

John

--
John K. Prentice    [e-mail] (Internet)
Dept. of Physics and Astronomy, University of New Mexico, Albuquerque, NM, USA
Computational Physics Group, Amparo Corporation, Albuquerque, NM, USA

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Date: 13 Feb 91 23:23:56 GMT
From: usc!wuarchive!emory!rsiatl!nanovx!chara![e-mail]  (Don Barry)
Organization: Center for High Angular Resolution Astronomy
Subject: E. Journal of the Astro. Soc. of the Atlantic, Vol. II, No. VII
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                        THE ELECTRONIC JOURNAL OF
                THE ASTRONOMICAL SOCIETY OF THE ATLANTIC

                    Volume 2, Number 7 - February 1991

                       ###########################

                            TABLE OF CONTENTS

                       ###########################

         * ASA Membership/Article Submission Information

         * Saturn's Great White Spot - Don Barry

         * When the Light Gets in Your Eyes, You Shouldn't Have to
            Drive to the Country - James Smith and Ken Poshedly

         * Stephan's Quintet - Bob Bunge

                       ###########################

                       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] or [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, Jim Bitsko, Bill Bagnuolo
         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.


                          SATURN'S GREAT WHITE SPOT

                                by Don Barry

        What an exciting time the past decade has been for observers and
    theorists of dynamic astronomy!  Only four years ago, observers were
    treated to the first reasonably bright stellar explosion in centuries
    (Supernova 1987A in the Large Magellanic Cloud galaxy).  In the last
    two years, transient phenomena have recurred on the giant planet
    Jupiter (the disappearance of the South Equatorial Belt and darkening
    of the North Temperate Belt).  The unmanned space probe VOYAGER 2
    found long-lived dynamic structures on the planet Neptune (the Great
    Dark Spot (GDS) and the "Scooter" cloud) in 1989.

        Infrared astronomy now permits routine monitoring of the
    vicissitudes of volcanic eruptions on Jupiter's Galilean moon, Io,
    and yet another Sol system moon is now known to exhibit dynamic
    behavior (geysers on Neptune's largest known satellite, Triton).
    Our own CHARA program now images binary stars with periods down to
    three months (Capella).

        This is not "old-fashioned", static astronomy.  Now we have a new
    dynamic event on our hands, and it is from one of the normally most
    stable planets:  The Jovian world named Saturn.

        S. Wilber reported sighting a bright white feature on Saturn's
    disk just after Sun "set" on September 25, 1990.  Within the next
    three nights, dozens of reports had reached the Central Bureau for
    Astronomical Telegrams, including a report of the "spot" from the
    venerable Clyde Tombaugh, discoverer of the planet Pluto in 1930.
    Wilber's report, after three subsequent nights of observation, was
    that the spot appeared brighter and more condensed initially, though
    the seeing was poorer on subsequent evenings.  It was first seen near
    the center of the planet's disk, on the southern side of the North
    Equatorial Belt.  One observer (R. Tatum of Richmond, Virginia) even
    saw the spot near Saturn's limb with just a ten-centimeter (four-inch)
    refractor telescope.

        By September 30, the spot had already evolved considerably.  M.
    Kidger, of the Instituto de Astrofisica de Canarias, reported a major
    disruption of the North Equatorial Belt in the region of the spot.  To
    the west of the spot, the belt was very dark and active, but it had
    faded and narrowed considerably to the east.

        Then the spot began lengthening, stirring up activity in the
    entire equatorial zone of Saturn.  ASA members Nils Turner and Don
    Barry first observed the spot on October 3 with the forty-centimeter
    (sixteen-inch) CHARA instrument.  They reported the object to be
    brilliant and somewhat elongated.  Dan Green of the Central Bureau for
    Astronomical Telegrams (CBAT) described it at that time as being
    "almost fluorescent" in appearance.

        An observation only a few hours later, by Ralphe Neill of
    Melbourne, Australia, revealed the equatorial belt transformed from
    its usual indeterminate yellow color to a thin brownish line with
    evidence of scalloping.  The spot itself was a prominent oval, but the
    overt effects extended 120 degrees around the planet.  Ralphe's next
    observation on October 14 showed the brightened area surrounding the
    spot extending about 150 degrees around the planet.  He also observed
    obscured areas within the spot and surmised it had split into three
    different zones.

        Several observers used a little of the old and a little of the new
    for their observations.  Brent Archinal took CCD exposures using the
    venerable sixty-centimeter (24-inch) reflector of the United States
    Naval Observatory (USNO).  Brent confirmed his photographs with visual
    detail noted by observers with the USNO's thirty-centimeter (twelve-
    inch) Alvan Clark refractor.

        By this time, it was well established that the spot did not rotate
    with the planet.  Transiting some 24 minutes ahead of Saturn's rotation
    (Saturn rotates on its axis once every 10.23 Earth hours), the spot was
    observed to move some 1,440 kilometers (900 miles) per hour faster than
    the planet's "surface" (atmosphere, actually) in rotation.

        Ralphe's speculation of "twinning" was in fact prognosticated by
    observations from Kidger four days previously (October 10, in better
    seeing) of two smallish, extremely brilliant white spots superimposed
    upon the original spot area, which intriguingly appeared when the
    original spot was near the Saturnian longitude where it initially
    appeared.  Kidger also noted a larger and less spectacular spot in
    the trailing border of the original Wilber spot.

        A very provoking observation by Stephen J. O'Meara of SKY AND
    TELESCOPE magazine on October 16 revealed a dark marking near the
    trailing edge, almost as if a cloud shadow were projecting onto the
    planet's equatorial zone.  He also noted two other brightening spots
    offset by sixty and one hundred degrees from the Wilber spot.  The
    North Equatorial Belt had faded dramatically since the onset of spot
    activity.

        A working theory was advanced by Phil Marcus (Berkeley Univer-
    sity) in NATURE (1988, 331, page 693) to explain spot formation and
    endurance in gas giant atmospheres.  His model, which was tested
    hydrodynamically with a large rotating water tank (Sommeria et al.,
    same issue) required the existence of horizontal shear (i.e., differ-
    ential rotation) which is now a well-observed phenomenon on all of
    the Jovian planets.  The shear tends to create turbulent vortices,
    which occasionally coalesce into larger vortices.  If the shear is
    sufficiently large and the coalesced vortex exceeds a critical size,
    then decay can be inhibited, leading to long-lived active structures.
    None of this explains, however, why Saturn has remained quiescent
    since 1933, when the last large series of spots were seen in its
    atmosphere.

        Saturn has currently disappeared behind the Sun.  When the planet
    reappears, much of this activity may have ended and the "surface"
    returned to quiescence.  While it remains in view, though, several
    theories of spot formation and propagation will get a workover.  Ama-
    teur and professional astronomers alike will wait to see what Saturn
    does next.  Even the Hubble Space Telescope (HST) is in on the act,
    taking occasional photographs in blue and near-infrared as its Earth
    orbit and the decreasing Sun-Saturn angle permits.  From a newly
    dynamic planet, new science is even now being born.

        About the Author -

        Don Barry, President of the Astronomical Society of the Atlantic
    (ASA), is an astronomer with the Center for High Angular Resolution
    Astronomy (CHARA) currently pursuing his Ph.D..  Don's professional
    interests include optical interferometry, binary astrometry and
    photometry, and innovative instrumentation.  An active amateur as
    well, Don's interests include telescope making, antique instruments,
    and fostering amateur-professional collaborations.

        Don is also the author of the following EJASA articles:

        "Astronomy Week in Georgia" (August 1989)
        "Profiles in Astronomy: Albert Whitford" (September 1989; an
    interview with Edmund Dombrowski and Sethanne Howard)
        "Alar Toomre: Galactic Spirals, Bridges, and Tails" (October
    1989; an interview with Edmund Dombrowski and Sethanne Howard)
        "Observing the Wreaths of Winter" (December 1989)
        "The Mayall Four-Meter Telescope" (May 1990)
        "A Southern Travel Diary: An Observer's Tale" (August 1990)


                        WHEN THE LIGHT GETS IN YOUR EYES,
                   YOU SHOULDN'T HAVE TO DRIVE TO THE COUNTRY

                         by James Smith and Ken Poshedly

        Our cities have become marvels of lighting, with night turned to
    day and illumination filling every highway, byway, and alley.  Light
    is no longer a rarity:  Now in excess, it is a nightly annoyance,
    intruding where it is not wanted or needed, in our windows, yards,
    and eyes.

        Urban astronomy is now a subject of nostalgic interest only.  The
    growth of metropolitan regions and the increasingly wasteful use of
    light has raised sky brightness for most suburban residences to the
    point that faint-object astronomy is no longer practical near cities.

        Amateur astronomy usually involves observation of low-contrast
    objects or dim stars against the night sky background.  In competition
    with the cast-off glow of street lights, buildings, parking lots, and
    outdoor advertisements, dim celestial objects invariably lose the
    battle.  Dark, light-free skies where the Milky Way can be seen in
    all its glory now require excursions with telescope and observing
    equipment 80 to 160 kilometers (50 to 100 miles) out of town.

        For professional astronomers, the celestial situation is even more
    serious.  Urban sky glow threatens (and in some regions of the country
    has already doomed) professional observatories.  Palomar Mountain in
    California, home to the famous five-meter (200-inch) telescope, is now
    magnitude-limited by sky glow from the city of San Diego.  Mount Wilson
    Observatory's 2.5-meter (100-inch) telescope was completely retired in
    1986, primarily because of light pollution from local developments.
    The major national facility at Kitt Peak in Arizona was threatened by
    light pollution in the late 1970s and has been saved only by aggressive
    implementation of strict lighting codes in nearby Tucson, which has
    doubled in size over the last decade.

        Outdoor lighting is essential to modern society, but it should be
    used wisely.  Most light pollution results from poorly-designed light
    fixtures, unshielded lights and misapplied light sources.  Most light
    pollution is unnecessary!  The most effective way, therefore, of
    reducing light pollution is to require correctly designed light
    fixtures which illuminate the ground and not the sky.

        Georgia State University's (GSU) Hard Labor Creek Observatory
    illustrates some examples of 'good' lighting.  All outside illumination
    is generated by low-pressure sodium lamps, which are the most cost-
    efficient and the most easily filtered type known for general-purpose
    lighting.  All fixtures are shielded with no light emerging above the
    horizontal.  The only fault of this lighting is that it must be kept
    on at all night-time hours due to state-government insurance regulations.
    Many other forms of lighting can and should be restricted to the hours
    they are needed, both to save costs and reduce light pollution.

        The aim of light pollution control is not to abolish outdoor
    lighting but to encourage responsible, efficient, and well-engineered
    lighting that directs light to the ground where it is needed.  A
    number of future ASA activities will stress the distinction between
    good and bad lighting and explore techniques for encouraging the
    adoption of efficient, non-polluting outdoor illumination.

        For more information on the problems and solutions to light
    pollution, please refer to the article "Stopping Space and Light
    Pollution", written by Larry Klaes and Phil Karn, published in the
    September, 1989 issue of the EJASA.

        About the Authors -

        Ken Poshedly, ASA Secretary, is a long-time amateur astronomer
    and maintains an ongoing interest in astronomical writing and
    historical astronomy.  Ken's interests also include education and
    Volkswagens.  A technical writer by profession, Ken has a degree in
    Journalism from Kent State University in Ohio.  Ken assists with
    editing and electronic management of the hardcopy ASA Journal's
    computerized assembly.

        Ken is the author of "Did Kepler Fake the Evidence?" in the
    May 1990 issue of the EJASA.

    James Smith is a community representative of Georgia Power,
    Inc., a division of the Southern Company.  He has supported
    efforts to foster communication between power utilities and
    those with special lighting needs and concerns.


                              STEPHAN'S QUINTET

                                by Bob Bunge

        Stephan's Quintet is a popular "challenge object" for astronomers
    in the constellation of Pegasus, with five galaxies situated in a
    single field of view.  Although this galactic cluster is usually con-
    sidered a challenge for a twenty-centimeter (eight-inch) telescope,
    I would not rule out seeing these galaxies with smaller telescopes,
    even at 90 millimeters (mm), assuming the Quintet is not confused
    with nearby NGC 7331 at magnitude 9.5, which can be seen in a 60 mm
    refractor.

        Stephan's Quintet was discovered visually in 1877 by astronomer
    Edouard Stephan at the Marseilles Observatory in France, using a
    78.75-centimeter (31.5-inch) telescope whose mirror was constructed
    and installed by Leon Foucault (1819-1868) in 1864.

        Stephan's Quintet is composed of the following galaxies:

        RNGC     UGC      Size          Magnitude (Relative)

         7317     N/A      N/A           13.6
         7318A    12099    1.7 x 1.2'    13.1 connected with 7318B
         7318B    12100    1.7 x 1.2'    13.1 connected with 7318A
         7319     12102    1.6 x 1.2'    13.1
         7320     12101    1.9 x 1.0'    12.7

        The fainter magnitudes in the RNGC can be very misleading.  While
    group member 7317 is listed in the RNGC with a photographic magnitude
    of 15.5, the same galaxy is listed in the NGC 2000.0 with a visual
    magnitude of 13.6.  Indeed, 7317 is the dimmest member listed in NGC
    2000.0.  The brightest, 7320, is listed at 12.7, but is a face-on
    galaxy with a low surface brightness and can sometimes be the hardest
    of the five to see.  Remember, visual magnitudes are about three
    quarters of magnitude brighter than photographic ones.  The visual
    magnitudes in the NGC 2000.0 were well researched and often reduced
    from photometric data.  In other words, I trust them.

        As an object, Stephan's is quite small (ca 3.5') and the galaxies
    are even smaller.  The combined brightness of all the objects may be
    within reach of a small telescope under good observing conditions with
    the use of medium-to-high magnification powers.

        The Uppsala General Catalogue (UGC) lists four of the five
    galaxies in the group.  All are smaller than 2' (arcminutes) in blue
    light.  Because the UGC is a complete catalogue of all galaxies north
    of declination -02, brighter than photographic magnitude 14.5, and
    larger than 1', one can assume the lone missing entry (RNGC 7317) is
    dimmer than 14.5 and smaller than 1'.  As a matter of interest, note
    the following:  Out of 12,940 UGC galaxies, 10,748 are smaller than
    2 arcminutes!

        A brief breakdown of UGC galaxies by size (Blue light):

        Size (arcminutes)       Number of objects

         <1.9                    1,989
          1.9                    232
          1.8                    474
          1.7                    613
          1.6                    763
          1.5                    783
          1.4                    918
          1.3                    1,039
          1.2                    1,382
          1.1                    2,014
          1.0                    2,122
         >1.0                    408

        Most galaxies in the Northern Hemisphere sky are relatively small.
    It has been my observation that many amateurs breaking away from
    observing the Messier objects and moving into the realm of faint
    galaxies often use too low magnification.  To see a small object, it
    helps to make it appear larger.  At medium powers, many telescopes
    will show a slight increase of contrast, helping the situation.
    Stephan's Quintet is an excellent example of this.

        I observed the Quintet several times with companions using a
    forty-centimeter (sixteen-inch) F/5.6 from a site in north central
    Ohio.  At 5,400 meters (1,800 feet), it is the fourth highest point in
    the state.  Each time we were disappointed to view only four of the
    galaxies.  Several years later, when that site became the Warren Rupp
    Observatory, I was able to observe the grouping with a 77.5-centimeter
    (31-inch) F/7 Newtonian and was amazed to easily see all five galaxies.

        I could also see the reason.  With a 28 mm eyepiece, the 77.5-
    centimeter telescope was working at almost 200 power.  We had been
    using no more than 120 power with the forty-centimeter instrument
    because "everyone knows not to use too high of power on deep sky
    objects."  The reason was due to galaxies 7318A and B being somewhat
    difficult to separate.  At 200 power, these galaxies reminded me of
    a pair of sunny-side up eggs in the skillet.  A later look through
    the forty-centimeter at 200+ power also revealed this "missing"
    galaxy.

        For more information on Stephan's Quintet and the constellation
    Pegasus, please refer to Brian Mason's article "Pegasus: Winged Horse
    of Autumn" in the September 1990 issue of the EJASA.

        About the Author -

        Bob Bunge may be reached at [e-mail].
    An active amateur with the Richland Astronomical Society, Bob
    corresponds actively on the FIDONET astronomy echo and also
    contributes to M-111, the newsletter of the Richland group.


     THE ELECTRONIC JOURNAL OF THE ASTRONOMICAL SOCIETY OF THE ATLANTIC

                       February 1991 - Vol. 2, No. 7

                         Copyright (c) 1991 - ASA


--
Donald J. Barry       [phone]         | [e-mail]
Center for High Angular Resolution Astronomy | President, Astronomical
Georgia State University, Atlanta, GA 30303  | Society of the Atlantic

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End of SPACE Digest V13 #154
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