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(meteorobs) RE: Leonids: 1966 rates revised down!



----Mensaje original-----
De:	Robert H. McNaught [SMTP:RMN@aaocbn2.aao.gov.au]
Enviado el:	sábado 24 de octubre de 1998 1:24
Para:	meteorobs@latrade.com; imo-news@imo.net
CC:	RMN@aaocbn2.aao.gov.au
Asunto:	Leonids: 1966 rates revised down!

 Dear Mr. McNaught,

	I read your last e-mail addresed to IMO list. I'm working from 1997 in the tractament of 1966 Leonids photographs in the University of Valencia (Spain).

	I know of photographs of Scott Murrell, J.W.Young and D.McLean but could you send me their e-mails to obtain more data (and images) of 1966 storm? I think you possibly know more people with photographs during the maximum.  

With the peak rates lasting for under 15 mins, not many photographs weretaken during this period.  If we do the sums for say one photographedLeonid every 2 seconds (assuming 1/sec is a statistical aberration),
with a photographic limiting mag of +3.0, a mag distribution index of 1.5
(and radiant elev fixed at 65 deg) one gets a "ZHR" of over 9,000 in the
camera field alone.  I would assume that the rates as seen by a visual
observer would be at least 3 times that of the camera field.  Thus even
with what I presume to be clearly underestimated numbers, the ZHR as
implied from the photographs is over 25,000.
[Josep Mª Trigo i Rodriguez]  For example, from the U. Minor A. Scott Murrell photography (12minutes exposure, limiting meteor magnitude 0 according Hawkins 1966) a ZHR(m<=+3.5) of approx. 16.000+-2000 has been obtained by me. Please note that a major ZHR will be obtained to visual observers because they have a limiting magnitude close to +6.5. 

Going back to my initial point, I feel a ZHR of 15,000 for 1966 cannot
be sustained on the basis of the photographic evidence, but it would be
interesting to have someone do a formal analysis of these photos.

[Josep Mª Trigo i Rodriguez]  But from this photograpy data we can obtain only the meteoroid flux in the magnitude range ]-inf.,0]. The extrapolation of these results to a minor magnitude range and comparison with visual data is approximate due to possible changes in the population index or the different perception of observers.  

Please send me suggerences, new photographic data, etc...

 Thank you,

			Josep Ma. Trigo i Rodriguez
			Dept. Astronomy and Astrophysics
			University of Valencia (SPAIN)