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Re: (meteorobs) Re: Cetids



>Jure & All,
>
>These meteors are Perseid-like in that they are bright, swift, and
>produce numerous trains.The radiant has not been pinpointed yet but
>it seems to be somewhere in the west or certral portion of Cetus.
>Some other experienced observers have reported this activity but like
>myself, they have not given this radiant the attention it needs.
>
>Clear Skies!
>
>Bob

The Cetid region is an interesting one during July and August, with three
notable periods of activity being produced by three somewhat different
streams. All of the streams are moving in retrograde orbits and are of
short period, something not seen among asteroids and comets with similar
orbital periods. Two of these three radiants just missed making the final
cut in my Meteor Showers book. The radar meteors typically exhibit very
fast speeds of 50-60 kilometers per second.

The first stream is active during the period of July 14 to 18, or from a
solar longitude of 111.6 to 114.4 degrees. The radiant is about right
ascension 25 degrees, declination -5 to -20 degrees. The declination spread
is because there seems to be a northern and southern branch. This is a very
active branch with visual support from previous catalogs. The reason I did
not include this stream is because of the declination spread. It has
produced more radar meteors than the other two Cetid streams and seems the
most active.

The second stream is active during the period of July 28 to August 1, or
from a solar longitude of 125.0 to 128.7 degrees. The radiant is about
right ascension 30 degrees, declination -9 degrees. It is second highest in
the number of radar meteors it produced among these three Cetid streams.
Once again there might be a northern and southern branch. There is a slim
possibility that this group is related to the mid-July group, but there is
absolutely no trace of anything from the Cetid region between these two
groups. It would seem probable that whatever created the first stream might
have been responsible for this stream after its orbit was perturbed.

Finally, the third Cetid group is rather weak in radar meteors, but still
has some visual observations backing it up. I think this is because it
occurs during the Perseids. The duration is from August 10-12, or solar
longitude 137.4 to 139.4 degrees. The radiant is about right ascension 20
degrees, declination -10 degrees. There is a large uncertainty in the
declination because of the small sample.

There is no indication among the data I have collected that indicates any
of these streams are annual or periodic, so I am not sure what to tell
anyone what to expect. All supporting observations were published between
the 1930s and the 1960s. Radar meteors are present up through 1969, while
some photographic evidence exists as recently as 1996.

Sincerely,
Gary


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