(meteorobs) The Perseids of 1991-1994 - so what *were* the maximum ZHRs?

[Daniel Fischer]

Every year when the Perseids are Moon-free, the IMO Shower Calendar entry reads like:
"The Perseids were one of the most exciting and dynamic meteor showers during the 1990s,
with outbursts at a new primary maximum producing EZHRs of 400+ in 1991 and 1992. Rates
from this peak decreased to ~ 100-120 by the late 1990s ..." Having travelled to Southern
France in *1993* and witnessed a huge outburst with an effective ZHR of 400+ there,
I was always wondering why the IMO stresses 1991 and 1992 instead, and so I finally
checked out the literature, coming upon three lengthy papers from the 1990's:

      Reference                   max ZHR for 1991       1992        1993       1994

Jenniskens,         A&A 295, 206 (1995)     500 (100)   400 (50)    230 (30)      -
Brown & Rendtel, Icarus 124, 414 (1996)     284 (63)    220 (22)    264 (17)   238 (17)
Jenniskens & al., MNRAS 301, 941 (1998)     350 (100)   550 (200)   250 (40)   190 (40)
                                            219 (63)    155 (22)    199 (17)   173 (17)

The first number is always the maximum ZHR value tabulated, followed by the error
(in the 3rd row it's the larger one of the + and - bars). Jenniskens & al. nowhere in
their paper clearly explain why they list *three* different ZHR values for each meteor
outburst (the 3rd being identical with the values in the 1995 paper) in their table 1;
the 2nd one seems to be the observed ZHR from Brown & Rendtel minus a background
component on which the extra peak sits.

There is also a cryptical statement in § 3.1: "The reported rates by Brown & Rendtel were
corrected by +15 per cent in order to match the ZHR scale of Jenniskens" - I thought the
ZHR formula was clearly defined and without personal fudge factors? Anyway, what *were*
the peak ZHR values then, which were recorded reliably in 1991 til 1994, regardless of the
contributions from the 'background' and the extra peak. And how do you define 'ZHR max'
anyway: How much and precisely how are the counts smoothed?


Lots of questions at 3:30 a.m., but I really want to know which year 'won' ...

Daniel