To: [email protected] From: "D.Staps" Subject: [SE] Shadow Band Observations at the Oct 24,1995 Eclipse in India
Hello from Wiesbaden (Germany),
1. I would like to hear about (astr. magazins, newspapers, internet-links) shadow band observations at the Oct 24, 1995 eclipse in India.
2. Has anybody an explanation, why at Fatepur Sikri there are no reported shadow band observations (the results of two known groups are negative) and at a site some ten kilometers away the shadow bands are very obvious???
Thank you for every answer. Dietmar Staps
From: "Carton, WHC" To: "'[email protected]'" Subject: RE: Shadow Band Observations at the Oct 24,1995 Eclipse in India
Sir, the cause of (2) might be the largeness of the free observation field. I had the same experience in La Paz, Baja California, with the eclipse of 11 July 1991: I was with some Dutch and Flemish amateur astronomers at the outside of the Campus of the Universidada Autonoma de Baja California Sur, with free panorama to the horizon spanning 270 degrees azimuth. We observed in the last about ten seconds shadow bands of about two meters wide that passed with tremendous speed, similar to the velocity that a passenger in an airplane see at take-off of the lights aside the runway. But the crew observers on the campus football field between the buildings, about 500 meters south from us, did not see any showband. My opinion: their view field was to limited by the surrounding buildings.
May be that in India a similar circumstance, for instance a forest, interfered and spoiled their view field. I found a "new" physical cause of shadow bands: interference of light along a sharp edge, the lunar horizon. I made a trigonometrical computation of how far on the ground two light rays
fall with a half wavelength phase difference: in La Paz about 4 meters. 4 meters = basis of a triangle to the 360.000 km high moon, that had an elevation of 82 degrees above the horizontal plane. But my interpretation is difficult to believe: the shadow bands must then have the same velocity as the lunar umbra, that was 600 meters per second, in La Paz. That sounds very hard observable for groundbased observers as we were. Greetings from Wil Carton, Kastanjelaan 25, 1901 SB Castricum, HOLLAND.
To: "JVG Send SE Listing" From: "Patrick Poitevin" Subject: Re: [SE] Shadow Band Observations at the Oct 24,1995 Eclipse in India
Dear Dietmar and others, I just finished an interesting investigation (also historically) and wrote an article about shadow bands.
In short :
- The flying shadows consist of undulating, moving bands or shades of light and shadow of some centimetres to some decimetres in width. The intervals between light and dark are alike and holes of some meters can come between the pattern.
- The bands are perpendicular to the edge of the moon's shadow further away from totality, and parallel with the edge of the shadow near totality. The band orientation runs parallel with the sun's crescent. The band orientation is the same near the central line before and after totality. Near the extremities of the totality zone, the band orientation has shifted up to 90 degrees.
- The turbulence, which is mainly the cause of the shadow bands, is under 2 kilometres altitude. Turbulence in the tropopause would have no impact on the shadow bands 2 to 3 seconds away from totality.
- Although they sometimes seem stationary, they can reach a speed of some meters per second. One shadow band can appear and disappear so fast that it moves individually over more than one meter before it dissolves.
- Shadow bands are visible from some seconds to various minutes before and after totality. During partial and annular solar eclipses, this could even be more. The bands themselves have the biggest contrast when there is space between them, and the least when the sun's crescent is at it's smallest.
- The contrast between light and shadow is bigger when wavelengths are shorter. So the shadow bands must be seen the best in blue light and the worst in red light. The band gap on scale (band spacing) is the square root of the wavelength near totality.
- Longer solar eclipses would have shadow bands with more contrast and linearity.
- Because the turbulence and the winds are not predictable, the explicit shadow bands can not be predicted. But with the meteorology they can be better understood.
Best regards, Patrick
From: Penaloza M A To: Patrick Poitevin Subject: Re: [SE] Shadow Band Observations at the Oct 24,1995 Eclipse in India
For a further and specialised theoretical discussion on the origin of shadow bands during TSE see:
Codona, J.L. (1986). "The Scintillation Theory of Eclipse Shadow Bands". ASTRONOMY AND ASTROPHYSICS, 164: 415-427.
Marcos A. Penaloza M. Essex University England.
To: "JVG Send SE Listing" From: "Patrick Poitevin" Subject: Re: [SE] Shadow Band Observations at the Oct 24,1995 Eclipse in India
Dear Marcos, (and others),
> For a further and specialised theoretical discussion on the origin of shadow bands during TSE see:
>
> Codona, J.L. (1986). "The Scintillation Theory of Eclipse Shadow Bands". ASTRONOMY AND ASTROPHYSICS, 164: 415-427.
Yes indeed, I did use also this reference. Thank you for sending this message. If you would come across other references, please let me know.
For your information, I did use following references on shadow bands:
References :
Guiness Book of Astronomie, Patrick Moore, 1983
Hemel en Dampkring 1912
Gazette astronomique, 8 juin 1912
History of Physical Astronomy
Observing and reporting shadow bands, Edgar Paulton, S&T September 1959
Eclipse Shadow band motions - An Illusion?, Edgar Paulton, S&T June 1963
A shadow-band experiment, Roger Burgess en Malcom Hults, S&T August 1969
Recording shadow bands at the March eclipse, Edgar Paulton, S&T February 1970
The problem of shadow band observations, Andrew Young, S&T May 1972
Shadow bands - solar eclipse Phantoms, Laurence Marchall, S&T February 1984
The scintillation theory of eclipse shadow bands, J. Codona, Astron. Astrophys. 1986
Shadow bands during the total solar eclipse of 11 July 1991, B. Jones en A. Jones, J. of Atmospheric and Ter. Phys., 1994
Shadow bands during the total solar eclipse of 3 November 1994, B. Jones, J. of Atmospheric and Ter. Phys., 1996
Total Eclipses of the Sun, Mabel Todd, 1894
The story of Eclipses, George Chambers, 1902
Eclipses of the Sun, Mitchell, 1923
De Natuurkunde in het vrije Veld, Minnaert, 1968
Best regards, Patrick
From: Jean Marc Lariviere To: [email protected] Subject: Re: [SE] Shadow Band Observations at the Oct 24,1995 Eclipse in India
At the risk of dragging the level of the discussion down a few notches, but since I do not have ready access to the reference documents listed previously, can someone sum up our present day understanding of the origin of shadow bands.
The mental picture I have is that of atmospheric lenses (ie. pockets or layers of different densities) giving rise to a phenomena akin to the shadows produced by the crests and throughs at the bottom of a pool. Is that a much too simplistic model? Jean Marc Larivi�re
From: Penaloza M A To: Patrick Poitevin Subject: [SE] Shadow bands bibliography
Bhatnagar, A., Jadhav, D.B., Jain, R.M., Shelke, R.N., Purohit, S.P., Bhonsle, R.V. and Pratap, R. (1982). Photoelectric Observations of Shadow Bands During 16 February 1980 Total Solar Eclipse from Japal-Rangapur Observatory. (1982). In Proceedings of INSA, Part A: Total Solar Eclipse of February 1980. Results of Observations, edited by S.K. Trehan, 48 A. INSA Publication, New Delhi, India; pp. 260-262.
Burgess, R.D. and M.E. Hults. (1969). A Shadow Band Experiment. Sky and Telescope, 38: 95.
Feldman, R.L. (1974). On Shadow Bands Accompanying Total Solar Eclipses. American Journal of Physics, 42: 1024-1026.
Gabiola, E. (1948). On Shadow Bands at Total Eclipse of the Sun. Popular Astronomy, 56: 353.
Henry, R.C. (1975). Atmospheric Phenomena During Total Solar Eclipse. Solar Eclipse 1973 Bulletin, Final Report 5. National Science Foundation, Washington, D.C. pp. 103-106.
Holden, E.S. (1883). Observations of the Diffraction Bands before and after the Total Phase - Solar Eclipse, May 6, 1883. Memories of the National Academy of Sciences, 2: 101.
Hultz, M.E., R.D. Burgess, D.A. Mitchell and D.W. Warn. (1971). Visual, Photographic, and Photoelectric Detection of Shadow Bands at the March 7, 1970 Solar Eclipse. Nature, 231: 255-258.
Klement, G.T. (1974). Observations of Short-Term Light Variations During the June 30, 1973 Solar Eclipse. Astronomy and Astrophysics, 37: 431-433 .
Marschall, L.A. (1984). Shadows Bands - Solar Eclipse Phantons. Sky and Telescope, 67: 116.
Marschall, L.A., R. Mahon and R.C. Henry. (1984). Observations of Shadow Bands at the Total Solar Eclipse of 16 February 1980. Applied Optics, 23: 4390-4393.
Quann, J.J. and C.J. Daly. The Shadow Band Phenomena. Journal of Atmospheric and Terrestrial Physics, 34: 577-583.
Seykora, E.J. (1979). Observations of Eclipse Shadow Bands and Related Phenomena. Applied Optics, 18 (21): 3538-3539.
Stanford, A.Y. (1973). On Shadow Bands Accompanying Total Solar Eclipses. American Journal of Physics, 41: 731-733.
From: Penaloza M A To: JVG Send SE Listing Subject: [SE] More shadow bands bibliography
Shadow bands during the total solar eclipse of 11 July 1991 B W Jones and C A L Jones J Atmos and Terrest Phys, vol 56, pp1535-1543 (1994)
Shadow bands during the total solar eclipse of 3 November 1994 B W Jones J Atmos and Terrest Phys, vol 58, pp1309-1316 (1996)
Abbe, C. (1900). Eclipse Shadow Bands and Correlated Atmospheric Phenomena. MWR, 28: 210-211.
Douglass, A.E. (1925). Cause of Shadow Bands. BAMS, 6: 150-151.
Feldman, R.L. (1935). Shadow Bands Caused by Diffraction. Am. Assoc. of Phys. Teachers; 6 pp. (mimeo).
Rotch, A.L. (1908). The Eclipse Shadow Bands. Harvard College Astron. Obs. Annals, 58, pt. 3; pp. 217-222.
Talman, Ch. F. (1906). Observations of "Shadow Bands" without an Eclipse. MWR, 34: 227-???
Watts, H.M. (1925). Shadow Bands During the Period of Greatest Obscuration - Partial Eclipse of the Sun, Philadelphia, Jan. 24, 1925. Popular Astronomy, Northfield, Minniapolis, 33: 236-240.
Wylie, C.C. (1925). Quoted on "Cause of Shadow Bands". BAMS, 6: 150-151.
BAMS = Bulletin of American Meteorological Society, Milton, Massachusetts MWR = Monthly Weather Review, U.S. Weather Bureau, Washington, D.C.
Hoping it will be very useful to you, regards. Marcos Penaloza Essex University England
From: "M. Jahan Miri" To: "'[email protected]'" Subject: RE: Shadow Band ...
On Fri, 13 Nov 1998, Carton, WHC wrote: Patrick, your quote "- The ..." supports my interpretation, that shadow bands are caused bij interferention of the last light rays along a sharp edge (the moon's circumference).
So, is it correct to conclude that SBs are due to "diffraction pattern at the edge of the Moon"? Or, is it that they are caused by "scintillations in the Earth atmosphere"? I believe the latter interpretation was also given on this List, earlier. Regards, Jahan [IASBS, Zanjan, Iran]
From: Barrie Jones To: SOLARECLIPSES Subject: Re: [SE] Shadow Band ...
Shadow bands are a scintillation phenomenon, in which the thin crescent of the Sun interacts with density variations in the atmosphere to produce an interference pattern on the ground. The density variations evolve, and move with the winds, hence the band's motion. A related phenomenon are the moving light and dark patches on the bottom of a swimming pool, though here its variations in the water surface, not the bulk density, that give rise to the interference. Barrie W Jones The Open University UK
From: Penaloza M A To: Patrick Poitevin Subject: Another reference
Codona, J.L. (1991). The Enigma of Shadow Bands. Sky & Telescope, 81: 482-487.
From: "Carton, WHC" To: "'[email protected]'" Subject: RE: [SE] Shadow Band Observations at the Oct 24,1995 Eclipse in India
Patrick, your quote "- The bands are perpendicular to the edge of the moon's shadow further away from totality, and parallel with the edge of the shadow near totality. The band orientation runs parallel with the sun's crescent. The band orientation is the same near the central line before and after totality. Near the extremities of the totality zone, the band orientation has shifted up to 90 degrees." supports my interpretation, that shadow bands are caused bij interferention of the last light rays along a sharp edge (the moon's circumference). In books about physics of technical optics, for instance by prof. Van Heel, interference and deflection of light along a sharp edge is graphically shown as a waving pattern between the area of fading light and the area of total shadow. That was exactly what I saw in La Paz, but on a scale thousand times magnified when I compare it with the Fresnel-Young experiment in a laboratory. Greetings from Wil Carton.