(meteorobs) IMO METEOR SUMMARY REPORT: 11/12 Aug 2004, Lew Gramer (GRALE)
Lewis J. Gramer
lgramer at upstream.net
Tue Aug 24 19:39:08 EDT 2004
As mentioned, I noticed that my Perseid rates were increasing toward the
end of this session, even though the moon had risen. I wondered why!
And the usefulness of my "NAMN-Report.xls" Excel spreadsheet was really
brought home to me on this report: notice in my original report I divided
my whole observing session into THREE EQUAL periods - each less than one
full hour of Effective Observing Time (Teff = total time minus breaks and
meteor recording "dead time"). As I mentioned in a prior report from this
week, this is NOT the normally recommended way of dividing sessions into
Periods - in either the IMO or the old AMS reporting methods.
However, I did this for two reasons... First, the Period Summary done in
this way does give a very clear picture of the relative strength of the
Perseids as the session progressed - and of their changing magnitudes!
Second, while entering my report I'd noticed that my Perseid rates were
noticeably increasing as the night neared its end, DESPITE the moonrise,
and the fact that my LM was steadily declining, and the PER radiant was
already well up in the sky by the time my first period began.
I really began to wonder why this would be - I had not thought that the
PERs were known for sudden, rapid increases in rates during their (back
ground) peak night! So I asked myself what the effect of "sampling bias"
(i.e., choice of periods to sum and average over) might be on my rates?
I experimented with a series of different Period divisions. (See the
end of this message for the various "experimental period summaries".)
Notice the way I reported this session to IMO clearly shows the PERs
were in fact BRIGHTENING very steadily as the night went on. And this
was apparent BEFORE the moon rose and LMs went down, as well as after.
(This brought to mind the discussion we had on 'meteorobs' recently,
of the evidence supporting a steady increases in the brightness of the
Geminids as they approach and pass their primary peak each year...)
However, some of the other Period samplings did not show this steady
brightening very clearly at all, e.g., see the last sampling, where I
divided my session in 20-minute periods instead of 51-minute periods.
In this Period Summary, the PER average magnitudes appear to vary
much more noisily - the brightening trend is quite difficult to see!
And I would imagine, that if I used the IMO formula to calculate 'r'
values and "effective ZHRs" for each of these very narrowly divided
periods, a similar "scatter" of results might show up... This really
reminded me of the saw, "There are lies, d*mn lies, and statistics!" :)
Obviously, when all individual meteors are entered in IMO's database,
these sampling effects can be easily corrected for. However, I found
this a very interesting little "experiment" in analyzing my own data.
Clear skies to all!
Lew Gramer
Period Summary (three equal-Teff periods, as reported to IMO)
PER Spor
Per Start End Teff LM N Mavg N Mavg
--- ----- ---- ---- ---- ------- ---- ------- ----
1 5:10 6:10 0.85 6.65 28 2.79 5 3.40
2 6:10 7:24 0.86 6.50 32 2.50 11 3.36
3 7:24 8:33 0.84 6.33 38 2.14 14 3.39
Period Summary (IMO method, bottom loaded)
PER Spor
Per Start End Teff LM N Mavg N Mavg
--- ----- ---- ---- ---- ------- ---- ------- ----
1 5:10 6:20 1.00 6.66 35 2.89 7 3.43
2 6:20 8:33 1.54 6.39 63 2.20 24 3.40
Period Summary (IMO method, front-end loaded)
PER Spor
Per Start End Teff LM N Mavg N Mavg
--- ----- ---- ---- ---- ------- ---- ------- ----
1 5:10 7:07 1.54 6.58 58 2.65 15 3.47
2 7:07 8:33 1.00 6.34 40 2.15 15 3.30
Period Summary (AMS method, bottom loaded)
PER Spor
Per Start End Teff LM N Mavg N Mavg
--- ----- ---- ---- ---- ------- ---- ------- ----
1 5:10 5:49 0.54 6.61 15 2.40 4 3.50
2 5:49 7:07 1.01 6.57 43 2.73 11 3.45
3 7:07 8:33 1.00 6.34 40 2.15 15 3.30
Period Summary (AMS method, front-end loaded)
PER Spor
Per Start End Teff LM N Mavg N Mavg
--- ----- ---- ---- ---- ------- ---- ------- ----
1 5:10 6:20 1.00 6.66 35 2.89 7 3.43
2 6:20 7:44 1.00 6.44 44 2.23 16 3.44
3 7:44 8:33 0.54 6.32 22 2.11 8 3.31
Period Summary (20-minute sub-periods)
PER Spor
Per Start End Teff LM N Mavg N Mavg
--- ----- ---- ---- ---- ------- ---- ------- ----
1 5:10 5:31 0.33 6.50 11 2.64 1 3.00
2 5:31 5:57 0.33 6.69 9 2.72 4 3.50
3 5:57 6:19 0.33 6.70 15 3.17 1 3.00
4 6:19 6:50 0.33 6.54 8 1.56 7 3.29
5 6:50 7:20 0.34 6.40 16 2.69 3 3.67
6 7:20 7:43 0.33 6.37 17 2.15 6 3.50
7 7:43 8:19 0.33 6.32 16 2.19 7 3.21
8 8:19 8:33 0.22 6.30 8 2.31 1 4.00
> -----Original Message-----
> From: meteorobs-bounces at meteorobs.org
> [mailto:meteorobs-bounces at meteorobs.org] On Behalf Of Lewis J. Gramer
> Sent: Tuesday, August 24, 2004 7:12 PM
> To: 'Global Meteor Observing Forum'
> Cc: dedalus at alum.mit.edu
> Subject: (meteorobs) IMO METEOR SUMMARY REPORT: 11/12 Aug
> 2004, Lew Gramer (GRALE)
>
>
> Here is the summary report for the final night... during my
> Florida Perseids campaign this year...
>
> A very interesting thread of questions came out of analyzing
> this night's data - having to do with how I divided my session
> into Observing Periods. I'll summarize that line of questions
> in a follow-up email to this one...
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