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Re: (meteorobs) Re: AKM video observations 12/99

Hello Cary,

I'm going through my mailbox in the order of message arrival, so I read
Bob's reply and your second mail only now.

> I understand that any intensified CCD can record down to 5th magnitude -
> this is a piece of cake - I've heard Sirko state this before.

5th mag is an arbitrary number. With the variety of lenses I currently 
have it can be anything between 5 (60 deg fov) and 9 (15 deg fov) mag.

> But the
> trick is in the automatic analysis as it is very easy to totally BURY
> yourself in hours and hours of tape that you have to watch to extract
> any information from.

No. The trick is _not_ to use any video tapes anymore but directly feed
the video signal into the computer an do an online analysis. No video
tapes are involved, unless I observe in the field or do some special
observations (Leonids) which I would also like to have a movie from.
 
> As I stated in my previous message - it's my understanding that the
> Metrec software can only log Magnitude 1 and brighter meteors.

I don't know where you got that impression from, but it's wrong. Right now
MetRec has a detection rate of about 80%. That is, on average 80% of all
meteors within the range of the camera are automatically detected (and
analysed). If you assume a typical population index between two and three,
the missing 20% are equal to a loss of lm of half a magnitude. That is, if
the camera is able to record meteors down to +5 mag, MetRec will find on
average all meteors down to +4.5 mag.

For comparison: A human observer watching a video tape finds in a
single pass about 85% of all recorded meteors, and at a second inspection
in the order of 95%. That is, MetRec is almost as good in detecting
meteors as a human observer.

> If this
> is correct then I pose the question what is the justification under
> utilizing the intensified CCD?  

Is that question answered now? :-)

> Also, I don't understand how a shower association can be tagged onto a
> meteor occurrence if it's radiant (or orbit) isn't being calculated.

Just as a visual observer does it: You do a backward prolongation of the
meteor path and check whether it intersects a known radiant assuming
typical position errors. In addition, the meteor velocity has to be
consistent with geocentric velocity of the shower, the meteor path has not
to be too long, and the shower needs to be active and above the horizon
at the given time.

Sirko

--
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*  Dipl.-Inform. Sirko Molau                  *                          *
*  RWTH Aachen, Lehrstuhl fuer Informatik VI  *              __          *
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