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 ; Fri, 15 Feb 91 20:50:54 -0500 (EST) Message-ID: <8bj8zoa00WBw44fU4M@andrew.cmu.edu> Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Fri, 15 Feb 91 20:50:47 -0500 (EST) 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 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 ---------------------------------------------------------------------- Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 11 Feb 91 12:40:07 GMT From: world!ksr!clj%ksr.com@uunet.uu.net (Chris Jones) Organization: Kendall Square Research Corp Subject: Apollo lunar surface photography References: <1991Feb10.022219.2255@zoo.toronto.edu> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu In article <1991Feb10.022219.2255@zoo.toronto.edu>, 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 clj@ksr.com {world,uunet,harvard}!ksr!clj ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 12 Feb 91 19:28:31 GMT From: crash!dang@nosc.mil (Dan Gookin) Organization: Crash TimeSharing, El Cajon, CA Subject: Re: Fire in Space References: <1991Feb11.185010.18933@eagle.lerc.nasa.gov> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu In <1991Feb11.185010.18933@eagle.lerc.nasa.gov> finley@snuffy.lerc.nasa.gov (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 ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 14 Feb 91 06:10:03 GMT From: unmvax!ariel.unm.edu!ghostwheel.unm.edu!john@ucbvax.Berkeley.EDU (John Prentice) Organization: University of New Mexico, Albuquerque, NM Subject: Re: Kevlar (was: Manoeuvring using rope and anchor) Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu > gregc@cimage.com 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 john@unmfys.unm.edu (Internet) Dept. of Physics and Astronomy, University of New Mexico, Albuquerque, NM, USA Computational Physics Group, Amparo Corporation, Albuquerque, NM, USA ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 13 Feb 91 23:23:56 GMT From: usc!wuarchive!emory!rsiatl!nanovx!chara!don@ucsd.edu (Don Barry) Organization: Center for High Angular Resolution Astronomy Subject: E. Journal of the Astro. Soc. of the Atlantic, Vol. II, No. VII Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu 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. asa%chara@gatech.edu or asa@chara.uucp 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, 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: 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. 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 rbunge@magnus.ircc.ohio-state.edu. 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 (404) 651-2932 | don%chara@gatech.edu Center for High Angular Resolution Astronomy | President, Astronomical Georgia State University, Atlanta, GA 30303 | Society of the Atlantic ------------------------------ End of SPACE Digest V13 #154 *******************