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RE: (meteorobs) Leonid eZHR question, plus others
Ed, be sure your Sine angle is in radians if that's what your calculator
requires.
However, with LM +4.2 and a one minute count of 22, that's not out of
line. I'm sure my highest one minute count of 18 would translate close to
3000. The point is that one minute of observation, from one observer is too
small a sample to be statistically useful. Check out the science of
statistics..dot it's a challenging, but rigorously mathematical subject! :-)
When I ran my rough EZHR's yesterday I used a 15 minute bin. And as I
stated, that was really pressing the envelope. I used that to figure peak
times, not actual ZHR's. When Rainer has the dozens of intervals for a
minute, then it becomes statistically significant. Until then, it's just
fun.
Wayne
----------
From: Ed Cannon[SMTP:ecannon@mail.utexasdot edu]
Sent: Wednesday, November 21, 2001 8:51 PM
To: meteorobs@atmob.org
Subject: (meteorobs) Leonid eZHR question, plus others
Last night I spent three or four hours catching up on everyone's
reports to Meteorobs -- a great read! This afternoon I read a
lot more mostly informal Leonid reports on the Space.com forum
pages -- more good reading.
Now I'm trying to do estimated ZHR just for fun using the formula
from this page: http://web.infoavedot net/~meteorobs/guidechap8.html
> b) Formula with an LM below 6.5
>
> (HR) (r)^6.5-LM
> ZHR = -------------------
> Sine A
But I think I'm getting outlandish results. So this is to
request a little help please. Here are some sample values --
what I saw in the one-minute period of 10:56:00-10:57:00 UTC on
Sunday.
Raw one-minute count = 22, so HR = 1320
r = 2 (Maybe this is too high for this year's Leonids?)
Limiting magnitude (LM) = +4.2 (Earlier it had been much better.)
Radiant height (A) = 55 degrees (I was at 31.4N, 103.4W, 850m.)
Sky obstruction = none (But I have a question about fog below.)
What are the right answers? I'm getting ZHR=7897, which can't be
right. Can it? What am I missing? I'm certain of my count. I
was writing in a 4"x6" tablet while watching the sky, about 60-65
degrees up in the NE. I didn't try to estimate magnitudes
(except for a few extremely bright ones), so it wasn't hard to
count them at those rates; I just marked a simple "1" for each
one as I saw it. If I saw two or three at once, it was just a
matter of two or three quick marks. If I saw them while turning
a page, I only had to remember those for a couple of seconds
before marking them down. For non-Leonids I wrote an "s". So I
feel good about my counts.
Other questions. First, I was wondering how to deal with fog.
My LM at 11:00 UTC was about 4.0, but I could see the really
bright ones down low in the sky. So I think that F=1.0, but the
sky wasn't really "unobstructed". Is there a transparency
factor? Or maybe that's in the LM value?
Second, I had taken the LM chart for Gemini out, but when I
looked up and of course saw Jupiter in the middle of it, I
wondered if it was possible to do a valid star count with a -2
magnitude planet in the field. (Relatedly, I wondered how many
novices, just a little newer than I, might have used the Taurus
star field and counted Saturn as a star.)
Third, I wonder if I was looking too far from the radiant. I
saw quite a few bright, very short ones in Leo but wonder how
many more I would have seen there if the center of my field of
view had been closer to the radiant. I was looking at about
alt. 60, azi. 45, so I guess I was looking at least 45-50
degrees away from the radiant, which put it near the edge of my
FOV.
Here are some things that may be of interest.
There are Houston Astronomical Society Leonid reports on this
page:
http://spacsun.ricedot edu/~has/Meteors.html
There's a 2-minute Leonids video (that I haven't seen yet) on
this page:
http://wwwdot caffreydot net/leonids.html
I gleaned those from the many Leonid reports on the Space.com
Web site that I read earlier today. The relevant URLs are too
long, but the area titles are:
"SPACE.com Uplink > Space Science & Astronomy > Leonid Meteor
Shower Sightings" (2001 Leonids only)
"SPACE.com Uplink > Space Science & Astronomy > Leonid Meteor
Shower: Share What You See!" (pages 1 and 2 are year 2000;
page three is year 2001 reports)
Finally, regarding my Leonids 2001 experience, imagine my
reaction when, at the motel in Fort Stockton, I discovered
that I had left my lawn chair and ground cover in Austin. So
I did my Leonids 2001 observing from the hood of my car. But
at least I remembered my warm clothes and footwear, pens and
tablet!
Ed Cannon - ecannon@mail.utexasdot edu - Austin, Texas, USA
http://wwwvms.utexasdot edu/~ecannon/meteorlinks.html
The archive and Web site for our list is at http://www.meteorobs.org
If you are interested in complete links on the upcoming LEONIDS, see:
http://www.meteorobs.org/storms.html
To stop getting email from the 'meteorobs' list, use the Web form at:
http://www.meteorobs.org/subscribe.html
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end
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