I remember reading about the "false dawn" in a novel about Africa when I was a child, but I'd never seen it until I became educated as an amateur astronomer about 20 years ago. I love seeing the ZL in the mornings in the fall, when the Pleiades appear to be enveloped in its glow. My most memorable observation of the ZL light occurred in the fall at the Wedge Overlook a few years ago. The sky was unusually dark and transparent, even for central Utah. As the ZL first became visible in the pre-dawn sky, I noticed that it wasn't simply the usual cone of brightness that I'd seen before; it was possible to trace a band of light all the way across the ecliptic, including a discernible brightening at the anti-solar point, the Geggenshein, my first observation of that phenomenon. Dave Bernson was with me, and of course, it was nothing new or unusual for him. It was he who identified the anti-solar point and the Geggenshein, and I later confirmed it at home on my star atlas. Alas, I think it was also the last time that I've seen the Geggenshein.
Kim, what direction is the ZL in? I once thought I saw it sort of to the south. Thanks, Joe
Hi Joe. The ZL generally occurs along the ecliptic - it is brightest, however, in the inner solar system and is therefore more visible when the sun is not too far below the horizon. Where you see it depends on where the ecliptic intersects your horizon. This varies throughout the year, just as the points of sunrise and sunset change from the same observing point. The ZL is generally most visible when the following also occur:(1) When the ecliptic is at a relatively steep angle to the horizon, which occurs in the northern hemisphere in the evening hours in the spring and in the morning hours in the fall. (2) When skies are dark and transparent - it doesn't take much light pollution or moonlight to obscure the ZL. (3) When you're looking for it. I think that because of (1) the "false dawn" is a year-round phenomon in equatorial regions. Can anyone confirm this? Also, there should be a corresponding "false evening twilight" that might last well after both civil and astronomical twilight have ended, but I've never heard of it described that way. There's a good discussion of the ZL and Geggenshein in the Observer's Handbook published by the Royal Astronomical Society of Canada. Kim -----Original Message----- From: utah-astronomy-bounces+kimharch=cut.net@mailman.xmission.com [mailto:utah-astronomy-bounces+kimharch=cut.net@mailman.xmission.com] On Behalf Of Joe Bauman Sent: Tuesday, August 22, 2006 2:46 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Zodiacal light Kim, what direction is the ZL in? I once thought I saw it sort of to the south. Thanks, Joe _______________________________________________ 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 ______________________________________________________________________
I really saw it, or at least recognized it as such, for the first time while out in the West Desert in the Spring of '05 with several others, about an hour or so after sunset; very cool phenomenon. --- Kim <kimharch@cut.net> wrote:
Hi Joe. The ZL generally occurs along the ecliptic - it is brightest, however, in the inner solar system and is therefore more visible when the sun is not too far below the horizon. Where you see it depends on where the ecliptic intersects your horizon. This varies throughout the year, just as the points of sunrise and sunset change from the same observing point. The ZL is generally most visible when the following also occur:(1) When the ecliptic is at a relatively steep angle to the horizon, which occurs in the northern hemisphere in the evening hours in the spring and in the morning hours in the fall. (2) When skies are dark and transparent - it doesn't take much light pollution or moonlight to obscure the ZL. (3) When you're looking for it.
I think that because of (1) the "false dawn" is a year-round phenomon in equatorial regions. Can anyone confirm this? Also, there should be a corresponding "false evening twilight" that might last well after both civil and astronomical twilight have ended, but I've never heard of it described that way.
There's a good discussion of the ZL and Geggenshein in the Observer's Handbook published by the Royal Astronomical Society of Canada.
Kim
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On Behalf Of Joe Bauman Sent: Tuesday, August 22, 2006 2:46 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Zodiacal light
Kim, what direction is the ZL in? I once thought I saw it sort of to the south. Thanks, Joe
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Rich: Were you able to see more than the usual bright tiangular shape above the horizon, i.e. across the entire sky and/or the Geggenshein? -----Original Message----- From: utah-astronomy-bounces+kimharch=cut.net@mailman.xmission.com [mailto:utah-astronomy-bounces+kimharch=cut.net@mailman.xmission.com] On Behalf Of Richard Tenney Sent: Tuesday, August 22, 2006 3:19 PM To: Utah Astronomy Subject: RE: [Utah-astronomy] Zodiacal light I really saw it, or at least recognized it as such, for the first time while out in the West Desert in the Spring of '05 with several others, about an hour or so after sunset; very cool phenomenon. --- Kim <kimharch@cut.net> wrote:
Hi Joe. The ZL generally occurs along the ecliptic - it is brightest, however, in the inner solar system and is therefore more visible when the sun is not too far below the horizon. Where you see it depends on where the ecliptic intersects your horizon. This varies throughout the year, just as the points of sunrise and sunset change from the same observing point. The ZL is generally most visible when the following also occur:(1) When the ecliptic is at a relatively steep angle to the horizon, which occurs in the northern hemisphere in the evening hours in the spring and in the morning hours in the fall. (2) When skies are dark and transparent - it doesn't take much light pollution or moonlight to obscure the ZL. (3) When you're looking for it.
I think that because of (1) the "false dawn" is a year-round phenomon in equatorial regions. Can anyone confirm this? Also, there should be a corresponding "false evening twilight" that might last well after both civil and astronomical twilight have ended, but I've never heard of it described that way.
There's a good discussion of the ZL and Geggenshein in the Observer's Handbook published by the Royal Astronomical Society of Canada.
Kim
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utah-astronomy-bounces+kimharch=cut.net@mailman.xmission.com
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On Behalf Of Joe Bauman Sent: Tuesday, August 22, 2006 2:46 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Zodiacal light
Kim, what direction is the ZL in? I once thought I saw it sort of to the south. Thanks, Joe
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Definitely saw the large triangular light cone extend fairly high into the sky, almost to zenith, though no further. --- Kim <kimharch@cut.net> wrote:
Rich: Were you able to see more than the usual bright tiangular shape above the horizon, i.e. across the entire sky and/or the Geggenshein?
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Anyone in the group have a burning intrest in history, particularly the Revolution? If so, I'd be happy to send a pdf file of an article I wrote, just published in the Daguerreian Society's Annual. It's about a daguerreotype I own -- a portrait of a Revolutionary War veteran, Dr. Eneas Munson. But I have to warn you, the file is pretty hefty. Best wishes, Joe
Hi Kim Out here in Hawaii we see the 'False Dawn' fairly easily 6 months out of the year and other times there seems to be a glow, though not too distinct of a triangle. As for a 'false twilight' gotta check that out ................ from what I saw this AM, as the sunrise approaches, the ZL is QUICKLY lost. When I arrived on site about 3:30, I did notice a glow that brightened into the ZL that could be followed up to the zenith, maybe the slight glow is the 'false twilight' but I've never heard of that event either. Either way, it sure was a lovely morning and a great sunrise at 10,000 ft. aloha Rob
Joe: Might make for an interesting article, along with other atmoshperic and/or astronomical phenomena that folks don't usually realize are there, such as the earth's shadow on the atmosphere, earthsine visible when the moon is a thin crescent, moon halos and moon dogs, etc. -----Original Message----- From: utah-astronomy-bounces+kimharch=cut.net@mailman.xmission.com [mailto:utah-astronomy-bounces+kimharch=cut.net@mailman.xmission.com] On Behalf Of Joe Bauman Sent: Tuesday, August 22, 2006 2:46 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Zodiacal light Kim, what direction is the ZL in? I once thought I saw it sort of to the south. Thanks, Joe _______________________________________________ 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 ______________________________________________________________________
I've got some pretty good pics as well and I'd be happy to share them. -----Original Message----- From: utah-astronomy-bounces+kimharch=cut.net@mailman.xmission.com [mailto:utah-astronomy-bounces+kimharch=cut.net@mailman.xmission.com] On Behalf Of Rob Ratkowski Photography Sent: Tuesday, August 22, 2006 3:59 PM To: Utah Astronomy Subject: RE: [Utah-astronomy] Zodiacal light
You're right! I'll have to work on this sometime. Thanks, Joe
Joe I might some photos that can help ......... RR _______________________________________________ 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 ______________________________________________________________________
participants (4)
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Joe Bauman -
Kim -
Richard Tenney -
Rob Ratkowski Photography