[Prev][Next][Index][Thread]
(meteorobs) Re: The Leonid Meteor Outburst of 1997
Hello,
> The Leonid Meteor Outburst of 1997
I want to add a few comments to this news flash.
> "This field is wide open," commented Leif Robinson, editor of Sky &
> Telescope magazine, at the recent Partners in Astronomy meeting in Toronto
> hosted by the Astronomical Society of the Pacific. "These new video cameras
> could open the door for amateur astronomers to make important research
> contributions to meteor studies that were difficult or impossible in the
> past."
I do not fully agree with this statements. So far our experiments have
shown, that you need an image-intensified video system for regular meteor
observations. Of course, you can record meteors without it (for example
for fireball-patrol type of observations), but then the efficiency drops
by about one order of magnitude.
> Even the simple task of visually counting meteors can be greatly improved
> through video imaging. For example, during the 1998 Geminid meteor shower
> astronomer Tony Phillips observed a 20 degree-wide patch of sky centered on
> the constellation Orion for 3 hours using an Astrovid 2000 CCD video camera.
> Video images were continuously recorded on tape while Phillips counted
> meteors by eye and recorded the counts in a notebook. The next day, a
> comparison of the video tape with Phillips's notebook revealed that the
> camera had captured twice as many meteors as the astronomer!
>
> "I have 20/20 vision and the limiting magnitude was +6 for both me and the
> video recording system," says Phillips. "It was a fair competition, but the
> camera recorded many more meteors than I did. The ones that I missed tended
> to be faint, short and fast moving. When I played back the tape they were
> there, as clear as day. If lots of amateurs begin using recording devices
> like this we may discover all sorts of new things about meteor showers. "
This contradicts my own experience. Two years earlier I recorded the
Geminid maximum from Germany with an intensified video system that had the
same field of view (20 deg), but a much better limiting magnitude of about
8.5 mag for stars. My personal lm was something around 6.2, but visually I
recorded more than twice as much meteors in less effective observing time.
Looking at the number of shower meteors this ratio becomes even worse for
video, since the smaller your field of view, the fainter the average
meteor you record and the lower the percentage of shower meteors. So far
there has been no occasion that my image intensified camera recorded more
meteors than me - neither during several Perseid or Leonid, nor during
this Geminid campaign!
> The video cameras atop Mauna Kea in 1997 saw about 150 meteors in less than
> 2 seconds. That corresponds to an hourly rate of 180,000 - 270,000 per hour,
> which is comparable to the activity seen over western North America during
> the great Leonids meteor storm of 1966.
This comparison makes no sense at all: If I observe a meteor, I just have
make the observing intervall very small (say 0.01 second) and immediately
I have "stormlike rates". The event of Kinoshita was probably one big
meteoroid desintegrating before entering the atmosphere (as suggested in
the paper), thus it has nothing to do with the great meteor storms of the
19th and 20th century.
BTW, in connection with meteor storm we do not use the term ZHR (zenithal
hourly rate) but EZHR (equivalent ZHR) to underline the fact, that the
duration is much shorter than one hour.
Best regards,
Sirko Molau
----------------------------------------
Sirko Molau -- Video Commission Director
International Meteor Organization
e-mail: video@imodot net
WWW : http://www.imodot net/video
----------------------------------------
To UNSUBSCRIBE from the 'meteorobs' email list, use the Web form at:
http://www.tiacdot net/users/lewkaren/meteorobs/subscribe.html
References: