RE: [Utah-astronomy] Bryce Canyon trip - Look for gegenschien please
Kim wrote:
At Bryce Canyon NP in June I had an interesting conversation with John Dobson regarding the gegenschein. I've always understood that the source of both the zodiacal light and gegenschein is sunlight reflected from interplanetary comet dust. In his characteristic way, John said, "NO!" According to John, the source is actually reflected sunlight from dust-size fused silica (glass) beads blasted from the surface of the Moon by impacts.
It is possible that I've missed an article, there doesn't seem to be much support for this statement in the journal literature. There are two possible causes: (1) dust in the interplanetary medium from comets and asteriod collisions and (2) dust from lunar impacts. Supporting evidence is stronger for a cometary and asteriod source - graphically illustrated by this year's earlier apparition of the once-in-forty year "great" Comet McNaught. http://antwrp.gsfc.nasa.gov/apod/ap070122.html. I. Possible Cause A: Kordylewski clouds That lunar libration clouds (Kordylewski clouds) at the Earth-Lunar L4 (leading) and L5 (trailing) points might exist have been speculated for some time. ( http://en.wikipedia.org/wiki/Image:Lagrange_points_Earth_vs_Moon.jpg ) The Earth-lunar L4 and L5 points are in the moving reference frame of the Moon's orbit. In the Earth-Moon libration system, points L2 (behind the Moon) and L1 (between the Earth and the Moon) would not be expected to be visible. I understand L3 is too unstable to be expected to hold dust particles. Kordylewski clouds are elevated areas of brightness either within the gegenschien or adjacent to it. See: Kordylewski 1961 http://adsabs.harvard.edu/abs/1961AcA....11..165K Krumm 1968 AAVSO http://www.homestead.com/cleopanther/files/AAVSO.pdf Recent dynamical modeling of the L4 and L5 points (Jorba 2000, A&A 364:327-338) indicates that such stable orbital regions can persist for up to 1,000 years. Freitas's studies related to a SETI search are often cited as failing to physically confirm these credible lunar libration cloud sightings. See - Freitas 1980 (in context of SETI search) http://www.rfreitas.com/Astro/SearchIcarus1980.htm Freitas 1983 (in context of SETI search) http://www.rfreitas.com/Astro/SearchIcarus1983.htm Freitas stated that his work could not rule-out the existence of micrometeorite clouds. In summary, there is no recent visible, radar, radio or infra-red confirmation of the existence of Kordylewski lunar libration dust clouds. II. Potential source B: Comets and asteriods Satellites with dust detectors including Helios, Pioneer 9, Galileo, Ulysses and Cassini have been used to trace the interplanetary dust medium out to about 3 A.U. It is not a local Earth-Moon phenomena. The dust disk has been imaged by Skylab in the 1970s, IRAS in the 1980s and by Clementine in the 1990s. IRAS satellite images from the 1980s revealed subbands of heightened illumination within the smooth zodicial light disk. ( Skyes (2005?), Fig. 3, http://www.lpi.usra.edu/books/CometsII/7024.pdf ). Through modeling, these bands are associated with the orbital paths of: a) Jupiter family comets with an inclination of 7 degs to the ecliptic. b) Halley family comets with an inclination of 33 degs to the ecliplitc. c) Istropically distributed Oort comet clouds. Hahn 2002 ( http://arxiv.org/abs/astro-ph/0204111 ). Hahn's modelling attributes 89% of the volume of interplantary dust within 1 AU to cometary sources. High altitude capture of interplanetary medium dust indicates their structure and composition is consistent with cometary or asteriod origin. See Sykes as Fig. 4. III. Contra-evidence: Lunar sodium atmosphere Spectroscopic studies of the Moon and anti-lunar point made since the mid-1990s indicates that there is a significant sodium atmosphere surrounding the Moon out to 2 or 3 lunar radii. The density of the thin sodium lunar atmosphere varies with the intensity of meteor showers such as Leonid storms in 1998 and 2001. See - Potter 2001 http://adsabs.harvard.edu/abs/2000JGR...10515073P Smith, SM 1999 http://adsabs.harvard.edu/abs/1999GeoRL..26.1649S When the Moon is between the Sun and the Earth, this sodium atmosphere is blown away from the Moon and around the Earth. The sodium wind "tail" has been imaged spectroscoptically at the anti-lunar point by professionals using a 1.2 meter telescope. Smith 1998. (It is not clear whether this sodium atmosphere could be detected by amateurs using modern CCD equipment.) The sodium gas is simply easier to detect - as compared to lunar micrometeorites or dust. Presumably, the impacts that increase the density of the sodium lunar atmosphere also replenish any lunar micrometeor dust in the Earth-Moon system. But the extent and volume of such replenishment is not known. Kim, in conclusion, there is little support in the journal literature that gegenschien is principally caused by reflection from lunar meteor dust. The weight of the literature is that the dust off of which gegenschien reflects has its source in comets, asteriods and the Oort cloud. This does not rule out contributions to gegenschien from lunar micrometeor dust or Kordylewski lunar libration dust clouds. Kordylewski clouds are probably a transient phenomena and without more continuous monitoring, it is unlikely their frequency and causes will be found in the near future. Part of NASA's return-to-the-Moon project is a professional program, using two dedicated RCT 14" robo-scopes to continuously monitor lunar meteor impacts on the Moon. ( http://www.nasa.gov/centers/marshall/news/lunar/photos.html ) Amateur members of the ALPO has been reporting such impacts for years. ( http://www.lpl.arizona.edu/~rhill/alpo/lunarstuff/lunimpacts.html ) The NASA program site listed above provides instructions for amateurs on how to image for lunar meteor impacts and software to automatically scan AVI files for meteor impact flashes. The ALPO site ( http://www.lpl.arizona.edu/~rhill/alpo/lunarstuff/AnnualShowers.doc ) includes a list of favorable meteor showers that might produce impact flashes. The next favorable dates for 2007 are Nov. 6, Nov. 18 (Leonids) and Dec. 14 (Geminids). - Kurt _______________________________________________ Sent via CSolutions - http://www.csolutions.net
Kurt, you have to understand John Dobson. His theories should not be classed with mainstream, peer-reviewed science in most cases. There may be something to his ideas, there may not be, but if you spend hours searching the Web for corroborration or refutation of some of his ideas, as you apparently did for the gegenschien theory, you probably won't get any closer to hard data in his camp. http://quanta-gaia.org/dobson/ Dobson doesn't think like a typical scientist although he does understand hard science. His ideas on cosmology and astronomy are not as well-known as his "sidewalk" telescope concept. But he's a package deal and if you like him, you tend to ignore the bits you can't quite reconcile. Most of us are not motivated to tell the emperor that he has no clothes, at least not yet. He's too entertaining; and besides it's not as if we are defending a thesis. On 9/9/07, Kurt Fisher <fisherka@csolutions.net> wrote:
Kim wrote:
At Bryce Canyon NP in June I had an interesting conversation with John Dobson regarding the gegenschein. I've always understood that the source of both the zodiacal light and gegenschein is sunlight reflected from interplanetary comet dust. In his characteristic way, John said, "NO!" According to John, the source is actually reflected sunlight from dust-size fused silica (glass) beads blasted from the surface of the Moon by impacts.
It is possible that I've missed an article, there doesn't seem to be much support for this statement in the journal literature.
Kurt, I really appreciate all the research that you've done and the information that you provided. Thanks so much. I still couldn't find the web article to which I referred that mentioned the lunar impact connection to the gegenschien. (Should Gegenschien be capitalized for some reason? I've seen it both ways.) At the group site in Capitol Reef I/we easily saw the gegenschien at the anticipated position. Unfortunately there were so many green lasers and much-too-bright red flashlights that I realized that trying to photograph it would be futile. (Note to self: write a letter to the Nova editor about private star party etiquette.) I plan to go up to the Skyline Drive this week to try and photograph the gegenschien from there. In the mid-1990's I experimented with Kodak Ektachrome P1600 transparency film and successfully photographed the zodiacal light on several occasions. I tried to also capture the gegenschien but I was never sure that what I saw on the film wasn't the center-image brightening associated with fast camera lenses. I'm hoping that a digital image will help avoid this problem. Kim -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Kurt Fisher Sent: Sunday, September 09, 2007 8:34 PM To: utah-astronomy@mailman.xmission.com Subject: RE: [Utah-astronomy] Bryce Canyon trip - Look for gegenschien please Kim wrote:
At Bryce Canyon NP in June I had an interesting conversation with John Dobson regarding the gegenschein. I've always understood that the source of both the zodiacal light and gegenschein is sunlight reflected from interplanetary comet dust. In his characteristic way, John said, "NO!" According to John, the source is actually reflected sunlight from dust-size fused silica (glass) beads blasted from the surface of the Moon by impacts.
It is possible that I've missed an article, there doesn't seem to be much support for this statement in the journal literature. There are two possible causes: (1) dust in the interplanetary medium from comets and asteriod collisions and (2) dust from lunar impacts. Supporting evidence is stronger for a cometary and asteriod source - graphically illustrated by this year's earlier apparition of the once-in-forty year "great" Comet McNaught. http://antwrp.gsfc.nasa.gov/apod/ap070122.html. I. Possible Cause A: Kordylewski clouds That lunar libration clouds (Kordylewski clouds) at the Earth-Lunar L4 (leading) and L5 (trailing) points might exist have been speculated for some time. ( http://en.wikipedia.org/wiki/Image:Lagrange_points_Earth_vs_Moon.jpg ) The Earth-lunar L4 and L5 points are in the moving reference frame of the Moon's orbit. In the Earth-Moon libration system, points L2 (behind the Moon) and L1 (between the Earth and the Moon) would not be expected to be visible. I understand L3 is too unstable to be expected to hold dust particles. Kordylewski clouds are elevated areas of brightness either within the gegenschien or adjacent to it. See: Kordylewski 1961 http://adsabs.harvard.edu/abs/1961AcA....11..165K Krumm 1968 AAVSO http://www.homestead.com/cleopanther/files/AAVSO.pdf Recent dynamical modeling of the L4 and L5 points (Jorba 2000, A&A 364:327-338) indicates that such stable orbital regions can persist for up to 1,000 years. Freitas's studies related to a SETI search are often cited as failing to physically confirm these credible lunar libration cloud sightings. See - Freitas 1980 (in context of SETI search) http://www.rfreitas.com/Astro/SearchIcarus1980.htm Freitas 1983 (in context of SETI search) http://www.rfreitas.com/Astro/SearchIcarus1983.htm Freitas stated that his work could not rule-out the existence of micrometeorite clouds. In summary, there is no recent visible, radar, radio or infra-red confirmation of the existence of Kordylewski lunar libration dust clouds. II. Potential source B: Comets and asteriods Satellites with dust detectors including Helios, Pioneer 9, Galileo, Ulysses and Cassini have been used to trace the interplanetary dust medium out to about 3 A.U. It is not a local Earth-Moon phenomena. The dust disk has been imaged by Skylab in the 1970s, IRAS in the 1980s and by Clementine in the 1990s. IRAS satellite images from the 1980s revealed subbands of heightened illumination within the smooth zodicial light disk. ( Skyes (2005?), Fig. 3, http://www.lpi.usra.edu/books/CometsII/7024.pdf ). Through modeling, these bands are associated with the orbital paths of: a) Jupiter family comets with an inclination of 7 degs to the ecliptic. b) Halley family comets with an inclination of 33 degs to the ecliplitc. c) Istropically distributed Oort comet clouds. Hahn 2002 ( http://arxiv.org/abs/astro-ph/0204111 ). Hahn's modelling attributes 89% of the volume of interplantary dust within 1 AU to cometary sources. High altitude capture of interplanetary medium dust indicates their structure and composition is consistent with cometary or asteriod origin. See Sykes as Fig. 4. III. Contra-evidence: Lunar sodium atmosphere Spectroscopic studies of the Moon and anti-lunar point made since the mid-1990s indicates that there is a significant sodium atmosphere surrounding the Moon out to 2 or 3 lunar radii. The density of the thin sodium lunar atmosphere varies with the intensity of meteor showers such as Leonid storms in 1998 and 2001. See - Potter 2001 http://adsabs.harvard.edu/abs/2000JGR...10515073P Smith, SM 1999 http://adsabs.harvard.edu/abs/1999GeoRL..26.1649S When the Moon is between the Sun and the Earth, this sodium atmosphere is blown away from the Moon and around the Earth. The sodium wind "tail" has been imaged spectroscoptically at the anti-lunar point by professionals using a 1.2 meter telescope. Smith 1998. (It is not clear whether this sodium atmosphere could be detected by amateurs using modern CCD equipment.) The sodium gas is simply easier to detect - as compared to lunar micrometeorites or dust. Presumably, the impacts that increase the density of the sodium lunar atmosphere also replenish any lunar micrometeor dust in the Earth-Moon system. But the extent and volume of such replenishment is not known. Kim, in conclusion, there is little support in the journal literature that gegenschien is principally caused by reflection from lunar meteor dust. The weight of the literature is that the dust off of which gegenschien reflects has its source in comets, asteriods and the Oort cloud. This does not rule out contributions to gegenschien from lunar micrometeor dust or Kordylewski lunar libration dust clouds. Kordylewski clouds are probably a transient phenomena and without more continuous monitoring, it is unlikely their frequency and causes will be found in the near future. Part of NASA's return-to-the-Moon project is a professional program, using two dedicated RCT 14" robo-scopes to continuously monitor lunar meteor impacts on the Moon. ( http://www.nasa.gov/centers/marshall/news/lunar/photos.html ) Amateur members of the ALPO has been reporting such impacts for years. ( http://www.lpl.arizona.edu/~rhill/alpo/lunarstuff/lunimpacts.html ) The NASA program site listed above provides instructions for amateurs on how to image for lunar meteor impacts and software to automatically scan AVI files for meteor impact flashes. The ALPO site ( http://www.lpl.arizona.edu/~rhill/alpo/lunarstuff/AnnualShowers.doc ) includes a list of favorable meteor showers that might produce impact flashes. The next favorable dates for 2007 are Nov. 6, Nov. 18 (Leonids) and Dec. 14 (Geminids). - Kurt _______________________________________________ Sent via CSolutions - http://www.csolutions.net _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.utahastronomy.com ______________________________________________________________________ This e-mail has been scanned by Cut.Net Managed Email Content Service, using Skeptic(tm) technology powered by MessageLabs. For more information on Cut.Nets Content Service, visit http://www.cut.net ______________________________________________________________________ Internal Virus Database is out-of-date. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.1/963 - Release Date: 8/20/2007 5:44 PM Internal Virus Database is out-of-date. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.1/963 - Release Date: 8/20/2007 5:44 PM
Kim, that's the exact reason that when I first got semi-serious about astrophotograpy, I made the decision that all imaging sessions devoted to deep-sky subjects would be done outside of the star-party venue. Even the term "star party" denotes a social occassion and once you get several people with varying agendas at an observing site, you lose control of your immediate environment. Lasers and flashlights aside, it also just gets too distracting. Star-parties- public or private- are generally not the place for any serious observational astronomy or data taking, most of the time. Even at a dark-sky site, a star party to me means that the social aspect is just as important, or more so, than pristine skies. Many "serious" amateurs do their important work solo, or those that they "star party" with share thier needs for darkness and lack of distraction. They talk at break time; lasers are not needed and red flashlights are kept discreet and un-noticed. You're not going to get that lucky with a come-one, come-all astronomical society star party in a national park. I now think that if one is at a star-party at a national park or monument, or on public land in general at a publicized event, one can reasonably expect to have to put up with annoying distractions. There's really no such thing as a "private" star party on public land, unfortunately, especially if it's publicized and a lot of beginners are in attendance. I've bitched about it myself and just got criticized for it, so it goes. I do feel sorry that your experience was compromised- I've been there myself and just decided to put the camera away, of necessity. On 9/10/07, Kim <kimharch@cut.net> wrote:
At the group site in Capitol Reef I/we easily saw the gegenschien at the anticipated position. Unfortunately there were so many green lasers and much-too-bright red flashlights that I realized that trying to photograph it would be futile. (Note to self: write a letter to the Nova editor about private star party etiquette.)
I wasn't really complaining as far as the imaging prospects went. - I sort of expected that, for the same reasons that you cite. And, I enjoy our private as well as public star parties as social events every bit as much as observing opportunities - maybe more so, since I'm starved for that kind of camaraderie here in Sanpete. I was annoyed, though, with folks who used way-too-bright flashlights and pointed them in every direction without regard for anyone in the vicinity. I'm also more than annoyed with persons who mark their territory with strings of red lights or flashing red lights around their tripods. There is simply no need for such gadgets at gatherings of other observers, and I'm not sure that they're even necessary at public star parties. With this issue, I'm really not content to simply shrug off the problem. I don't want to offend anyone, but some folks, perhaps newer SLAS members, really need a bit of (gentle) persuasion to leave all the lights at home. Kim -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Monday, September 10, 2007 9:17 AM To: Utah Astronomy Subject: Re: [Utah-astronomy] Bryce Canyon trip - Look for gegenschien please Kim, that's the exact reason that when I first got semi-serious about astrophotograpy, I made the decision that all imaging sessions devoted to deep-sky subjects would be done outside of the star-party venue. Even the term "star party" denotes a social occassion and once you get several people with varying agendas at an observing site, you lose control of your immediate environment. Lasers and flashlights aside, it also just gets too distracting. Star-parties- public or private- are generally not the place for any serious observational astronomy or data taking, most of the time. Even at a dark-sky site, a star party to me means that the social aspect is just as important, or more so, than pristine skies. Many "serious" amateurs do their important work solo, or those that they "star party" with share thier needs for darkness and lack of distraction. They talk at break time; lasers are not needed and red flashlights are kept discreet and un-noticed. You're not going to get that lucky with a come-one, come-all astronomical society star party in a national park. I now think that if one is at a star-party at a national park or monument, or on public land in general at a publicized event, one can reasonably expect to have to put up with annoying distractions. There's really no such thing as a "private" star party on public land, unfortunately, especially if it's publicized and a lot of beginners are in attendance. I've bitched about it myself and just got criticized for it, so it goes. I do feel sorry that your experience was compromised- I've been there myself and just decided to put the camera away, of necessity. On 9/10/07, Kim <kimharch@cut.net> wrote:
At the group site in Capitol Reef I/we easily saw the gegenschien at the anticipated position. Unfortunately there were so many green lasers and much-too-bright red flashlights that I realized that trying to photograph it would be futile. (Note to self: write a letter to the Nova editor about private star party etiquette.)
Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.utahastronomy.com ______________________________________________________________________ This e-mail has been scanned by Cut.Net Managed Email Content Service, using Skeptic(tm) technology powered by MessageLabs. For more information on Cut.Nets Content Service, visit http://www.cut.net ______________________________________________________________________ Internal Virus Database is out-of-date. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.1/963 - Release Date: 8/20/2007 5:44 PM Internal Virus Database is out-of-date. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.1/963 - Release Date: 8/20/2007 5:44 PM
Sorry I misunderstood you Kim; I was sure this was a complaint of imaging prospects: "At the group site in Capitol Reef I/we easily saw the gegenschien at the anticipated position. Unfortunately there were so many green lasers and much-too-bright red flashlights that I realized that trying to photograph it would be futile. (Note to self: write a letter to the Nova editor about private star party etiquette.) " Would it be fair to call it at least a "lament" then? ;o) On 9/10/07, Kim <kimharch@cut.net> wrote:
I wasn't really complaining as far as the imaging prospects went. - I sort of expected that, for the same reasons that you cite.
Lament - maybe. It would have been nice to capture an image of the gegenschien since we had been discussing it during the previous week. I really didn't expect to capture any images at Capitol Reef. I'll be donwloading my pics shortly and I'll post any that might be respectable. Kim -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Monday, September 10, 2007 9:55 AM To: Utah Astronomy Subject: Re: [Utah-astronomy] Bryce Canyon trip - Look for gegenschien please Sorry I misunderstood you Kim; I was sure this was a complaint of imaging prospects: "At the group site in Capitol Reef I/we easily saw the gegenschien at the anticipated position. Unfortunately there were so many green lasers and much-too-bright red flashlights that I realized that trying to photograph it would be futile. (Note to self: write a letter to the Nova editor about private star party etiquette.) " Would it be fair to call it at least a "lament" then? ;o) On 9/10/07, Kim <kimharch@cut.net> wrote:
I wasn't really complaining as far as the imaging prospects went. - I sort of expected that, for the same reasons that you cite.
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.utahastronomy.com ______________________________________________________________________ This e-mail has been scanned by Cut.Net Managed Email Content Service, using Skeptic(tm) technology powered by MessageLabs. For more information on Cut.Nets Content Service, visit http://www.cut.net ______________________________________________________________________ Internal Virus Database is out-of-date. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.1/963 - Release Date: 8/20/2007 5:44 PM Internal Virus Database is out-of-date. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.1/963 - Release Date: 8/20/2007 5:44 PM
participants (3)
-
Chuck Hards -
Kim -
Kurt Fisher