[meteorite-list] 1993/94 Perseids - The Night of Lights!

From: Becky and Kirk <bandk_at_meteoritecentral.com>
Date: Sat, 14 Aug 2010 09:03:26 -0500
Message-ID: <EDBFE72735A142BC9832FE230BB3A862_at_owner55652f88b>

Hi All,
Just a quick correction. Actually Greg reported some 20-25 meteors per hour
witnessed with a TOTAL night of watching at 183 meteors seen.

That is much less though than the 100 or more per hour that my friends and I
saw in 1993, but still very impressive indeed. Also----even more astounding
was that for about a 5 or 10 minute period, we were seeing about 1 every
10-15 seconds. I remember that one of the guys was timing it!

Thanks very much to Bernd for all of his great info!!

Best to all,
Kirk......:-)

----- Original Message -----
From: <bernd.pauli at paulinet.de>
To: <Meteorite-list at meteoritecentral.com>
Sent: Saturday, August 14, 2010 6:54 AM
Subject: [meteorite-list] 1993/94 Perseids - The Night of Lights!


Hello List,

Some of you may have been surprised when they read about more than
300 Perseids in the Sky & Telescope article I mentioned last night:

'Counts made from western Europe, the Canary Islands, and eastern North
America indicate the maximum zenithal hourly rate (ZHR) topped out at
more than 300 around 3:30 Universal Time on August 12th.'

This would make Kirk's and his friends' observation of 100 and even Greg's
183 look rather "average" but it's not like that at all because ZHR is the
total number of meteors an experienced observer with an incredible 360? view
would see under ideal conditions.

Let's see how ZHR > 300 translates into what was actually observed, i.e. the
actual HR (hourly rate or actual number of meteors observed). The formula
for
computing the actual number is:

ZHR = HR x r^ (6.5-LM) / sinA

r = usually 2.5 for the Perseids (called population index)
6.5 = a real dark sky (limiting magnitude of stars you can see)
LM = limiting magnitude in the part of the sky being watched
A = the altitude of the shower's radiant

Assuming almost ideal conditions (on the Canary Islands for example),
let's use LM = 6 and an altitude of 60? of the Perseid radiant (around
01:00 hrs after midnight), ... so we have:

300 = HR x 2.5^ (6.5-6.0) / sin 60?
300 = (HR x 2.5^0.5) / sin 60?
300 = (HR x 1.58) / 0.87
HR = (300 x 0.87) / 1.58
HR = 261 / 1.58
HR = 165

That's the actual number a single experienced person may have been able
to see under favorable conditions, so Greg's Lindh's number (HR = 183) is
quite close to that mathematical result and Kirk's and his friends' HR of
100 Perseids is still a very respectable number of meteors!

Happy Computing,
Happy Observing,
Clear Skies,

Bernd :-)

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Received on Sat 14 Aug 2010 10:03:26 AM PDT