[Prev][Next][Index][Thread]
(meteorobs) We are having fun now...
In no particular order,
Sirko says:
>Do you think that the shower rates calculated within the IMO are manipulated
>to look better?
Good heavens, no. I have never implied that IMO was "cooking" the books. I
just have an opinion, MY OWN, not an "official" AMS one, about numbers with
so many correction factors cranked in you wind up with 50% error bars.
Granted that that example is only one data point among many, but as long as
we are talking about contaminated data, how contaminated is the rest of the
sample with such data? Without error bars, the reader has no idea what's
happening. I had my wife, who lived, ate, drank, and breathed statistics
for many years in the market research world look over some of this
discussion and the data presentations. She said you never, never, ever
quote statistically derived numbers without including error limits.
>Have you ever investigated how short intervall for
>visual observers can be still containing meaningful data? Juergen Rendtel
>presented his investigation about this at the last IMC. Basically he found
>out, that you can calculate meaningful ZHRs for single observers down to ten
>minute intervalls, if the activity is very high.
You can plug any numbers you want into the various ZHR formulae, but that
doesn't make for good statistics. Having not read the paper, I can't say
anything directly about it, but very small samples make for big, big error
limits, and unless that's the only data you have, then it should probably
not be used in in analysis.
>By the way, a little earlier you complained that IMO gives only ZHRs
>without error bars. So what is the +/- 45?
It's on a data point. The lists and calendars don't included error bars.
By contrast the DMS "master list" gives error bars with every rate. I don't
intend to slam the IMO calendar, which is a great document that I carry (by
permission from IMO) a copy of on our Meteor Group Hawaii web site. I may
have a statistical quibble or two with some numbers, but the calendar rates
a big "A" in my book.
>There is simply no way to correct such observations since most important
>data is missing! If you do not know the limiting magnitude, you cannot
>even compare observations of two observers. If you do know it but have
>not recorded the brightness distribution, you don't know the population
>index.
When I learned about recording meteors in 1970, the AMS way, we recorded
(and still do) the LM, any sky obscuration, the cloud cover, and any changes
to these items during the session, as well as any breaks in observing. I
don't know what else you need for analysis. Here is where you can educate
me, what is the "brightness distribution"? Is that the little chart each
observer fills in with the numbers of meteors of different brightnesses? If
it is, all the data is present to make one, it just hasn't been done before
the analyst looks at it. What other data is missing?
And George chimes in:
>When I get the WGN journal, I often see
>analysis been performed giving credit to those whose data was used.
And when I get Meteor News, I often see the same thing. Granted we haven't
seen a MN for a while, but I trust that'll be rectified soon.
>To discover that my efforts have been
>pidgeonholed with little or no feed back would be discouraging to say the
>least.
There's a difference between pidgeonholed and archived. The AMS records are
an archive. The observers from end of the last century and the very
beginning of this one whose data is there are no doubt dead, but their names
and work lives on in the archives. When Dr. Olivier passed the baton to Dr.
Meisel, he was careful to chose someone with academic credentials and an
institutional affiliation that could care for the records appropriately.
When the time comes, I know Dr. Meisel will do the same, and I like the
thought of researchers having access to my data 100 or even 200 years from now.
Similarly my variable star observations in the AAVSO database live on.
Years after I made them, I see observations I made cropping up in the AAVSO
Monograph series. The pleasure of using my time under the stars to
contribute to the body of knowledge is the name of the game, not instant
gratification.
And Mark contributes:
>Since NAMN does publish 'masses of raw data'
Here's where I may need some education. Is everything necessary for
analysis included in the data published? What I've looked at are your
Summary pages on the web site, if you are presenting other data I haven't
found it. I didn't see anything about cloud cover, etc. Or does the 'F'
factor listed include all that? My ignorance again, I don't know what your
'F' is. How about observer location for radiant height?
>I, for one, would like to see an AMS update to the fine Olivier "Tables of
>Hourly Rates..." that I have here on my shelf.... :-)
And I, too. But as very well discussed by Jim Richardson last summer, there
is no money for professional work on visual meteor data. Someday, a few
dedicated amateurs with professional guidance? It would be great, wouldn't it?
Good night, all.
Jim Bedient
Follow-Ups: