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LEONID 2001 Observations: Shane L. Larson


Leonid Meteor Rate Graph
Leonid meteor rate, west facing, for about 1/3 of sky, as observed and recorded by Shane L. Larson, 17/18 November 2001. The times are to the closest minute, in Pacific Standard Time (UT = PST + 8 hr).
Raw Data File (ASCII Text, TAB delimited)
Leonid Meteor Rate Graph, IMO
Leonid meteor rate, from the International Meteor Organization. Their early reports can be obtained here.

LEONID STORM REPORT: 2001

Shane L. Larson

LOCATION: Cloverdale, CA
DATE: night of 17/18 November 2001
SESSION: 201

LAT: 38d 46.51m N (GPS)
LONG: 122d 57.80m W (GPS)
ALT: 556 ft (GPS)

ASIDE:

We had a good look at Comet LINEAR C/2000 WM1 in Perseus. It is definitely NOT a naked eye object, but I was able to sweep it up near Algol with a simple grid search using a 6" f/8 Dob. The core is obviously extended and not pointlike -- it reminds me of how Uranus or Neptune look, only white. The halo was very extended, but round without any obvious extensions in any direction; the edge was slightly irregular as you traced your way around the halo. I looked at it again later in the evening to see it move; about 18 arcmin in 228 min.

DATA BINNING:

I bin my meteor observations in brightness, rather than estimating the magnitude. The reasons for this are (a) I can't estimate magnitude values to save my life, and (b) when they are coming fast and furious, it is easier to bin my data (for me) by recording hash marks to tally meteors in 4 brightness classes.

I have 4 classifications:

  • X = "extreme" = meteors brighter than Jupiter (m = -2.54)
  • B = "bright" = meteors brighter than Sirius (m = -1.47)
  • M = "medium" = meteors with bright core, dimmer than Sirius
  • D = "dim" = vapor trails only, or no bright core

    When binning, I would maintain a count for about 5 minutes, then start a new count, which I could use to get the rate at different moments during the night. If I had thought hard about it before I went out, I would have prepared to do it in even time increments. In reality, I recorded until I ran out of room on the line in my logbook, then started a new count. The bins range in size from 3 to 7 minutes for the most part.

    The times listed in the data set were recorded to the closest minute; I didn't have time to jot down the seconds, since I was watching the sky! My watch was synchronized to within 5 seconds of the time provided over the network via Apple Computer's time server. The times are all in Pacific Standard Time (UT = PST + 8 hr).

    OBSERVATIONS:

    (1) Surprisingly, I wasn't seeing a lot of sporadic events early in the evening (before 11pm). Early on (before about 2am) I simply recorded individual sightings, classifying the meteors by the above scheme, noting the apparent length in degrees, and where in the sky I saw it. This gave me about 1/min (fast as I could record), and I was noticing about 1-3 others/min in my peripheral vision. This initial phase was facing due east.

    (2) The first Leonid we saw was probably the best of the night. It (X class) emerged from behind a tree in the east at 11:16pm PST, travelling almost due west. We picked it up just N of Gemini, and it didn't fade until it reached the neck corner of Pegasus. Handspanning across the sky, I estimated the length to be about 125 degrees (I checked in Starry Night, and the distance is about 115 deg). It took just over 3 seconds to cross the sky, and left a major vapor trail that persisted for some time. My memory of the event is of jumping out of the folding lounge I was occupying, pointing at this thing as it streaks across the sky, and screaming "THERE'S ONE! THERE'S ONE!" over and over again. :-)

    (3) The skies clouded over completely about 1:19am. I thought about giving up, but several of the bright ones were showing through the clouds, so I binned data in that way until about 1:54am. In all, I saw 23 meteors through the clouds.

    (4) At 1:54am the western half of the sky began to open up (progressing east until the whole sky was open), so I flipped my gaze to watch due west. The rates were high enough that I stopped recording individual events (except for some notable ones), and simply binned by brightness class. The highest total rates I saw were 14.33/min, and 11.75/min around 2:35am. The typical rate floated in the 5-10/min range for the better part of 2 hours.

    (5) Starting at about 3:25am, we began to get a significant bolide component to the storm. Whereas we hadn't noted a single bolide the entire evening, between 3:25 am and 3:56am, we noted 6 different bolide events, either directly or by seeing the flash on the ground and turning to see the vapor trail. It was FANTASTIC.

    (6) I called it a night at 4:00am. Between 1:54am and 4:00am, I recorded 846 meteors, giving 846/(126min) = 6.71 per minute. The average of each of my data sets is 8.27 per minute.

    I figure I was watching about 1/3 of the sky, so my all sky rate would have been (3 x 846)/(126min) = 20.14/min.

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