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(meteorobs) Fwd: Telescopic video of Leonids & Linearids SOON
NOTE: David is not a current subscriber of 'meteorobs': if you wish to
follow up on the following message - as I expect many of you will! - you
must MANUALLY put 'dunham@erols.com' in the "Cc:" line of your reply.
PS: David, if you wouldn't mind following up with a message to your own
distribution list, the sound tracks of these videos may also contain an
important poorly-observed feature of certain very bright meteors: sounds!
Simply mentioning that sound tracks from these videos ARE worth scanning
by the observer if bright fireballs are noted, would be very helpful.
Thanks!
Lew Gramer <owner-meteorobs@jovian.com>
------- Forwarded Message
Date: Tue, 09 Nov 1999 11:59:09 -0500
To: burke@surfsouth.com
From: Joan and David Dunham <dunham@erols.com>
Subject: Telescopic video of Leonids; & Linearids SOON
Everyone interested in the sky will be interested in the third item
below, a possible intense meteor shower during the next couple of nights
from Comet LINEAR, if you don't already know about it. But this is
being distributed to all observers on my occultation observer list,
mainly to encourage those with video capability for recording
occultations telescopically to use their equipment for recording certain
aspects of the Leonids that can not be recorded, or recorded as well,
with the mainly wide-field systems of dedicated meteor observers. This
is an opportunity for occultation observers to make some unique and
valuable observations in another field of astronomy. The major topics
are given below.
1. Telescopic video observations of Leonid meteors.
2. Leonids hitting the dark side of the Moon - especially the Americas.
3. Meteors from Comet LINEAR possible November 10-12 - Leonid preview?
________________________________________________________________________
1. Telescopic video observations of Leonids are sought, with and
without image-intensified systems. For example, observation with the
sensitive PC23C camera with any telescope are sought. Although an
audio record of shortwave time signals is nice if available, be sure
to give some visual cue to the time since when successful observation
tapes will be scanned, there is no access to the audio track. A
time/date stamp generator is ideal but if that is not possible,
passing a white card across the field of view (or briefly shining a
flashlight into it) at a known (recorded/written down) time works as
well. Timings to the nearest second are preferred.
Use the widest field of view (FOV) that your telescope/video
combination can achieve (use a focal reducer lens if you have one).
Observations are sought from 0h UT November 17 to 0h UT November 19.
Peter Gural, who is coordinating a worldwide effort to record
Leonids with wide FOV (20 deg. and more) intensified video systems, writes
about this:
"I had a thought yesterday that you may be interested in trying but
unfortunately I do not have time to coordinate another data collection
effort and will be out of the country for the Leonids. This has to do
with the narrow field of view imaging systems that your group uses. Dr.
Bob Hawkes of Mount Allison University (the video meteor guru) claimed
to have seen "jets" protruding perpendicular to several Leonid tracks in
last year's video. The physical phenomena is unknown at this time.
Conjectures are ejected material (explosively), discharges (lightning)
in the E-layer, or just pixel noise in the intensifiers. An interesting
project may be to record narrow field of view (telescopic video) to try
and resolve the question of the jets' reality. The drawback is that
with a narrow field of view, the chances of capturing a meteor are low.
Having a storm helps but there is no guarantee a storm will occur.
Alternatively, by having many telescopic video cameras operating, the
odds are greatly improved of capturing several meteors on tape. [In a
given area where several telescopes with video are available,] one could
set up a bank of several non-overlapping telescopic fields of view and
record away all night. Time stamps are nice but not required. Setting
the scopes pointing in the same region of sky (but non-overlapping)
would enable the possibility of a meteor traversing several cameras.
Best pointing would be 60 degrees elevation and 60 degrees from the
radiant. Above the north celestial pole is a possibility. All the
systems could be in a common site but again that is not required
[certainly, observations at any location in the world could potentially
catch some Leonids]. You would have to do the coordination of observers
and equipment [I will attempt that in the Maryland-DC-n. Virginia area;
others can coordinate other areas, as for grazes or asteroidal
occultations]. I can process the tapes after I get back. We will have
15 intensified cameras operating at various sites around the world but
all will have fairly wide 20-40 degree fields of view."
Peter S. Gural
Science Applications International Corp. (SAIC)
4001 N. Fairfax Drive, Suite 400
Arlington, VA 22203
Phone +1-703-816-5954
If you obtain a useful tape, send it (or a VHS copy) to Peter Gural.
Specify your observing location, preferably including longitude,
latitude, and height above sealevel (don't need to be as precise as for
occultations, although for some observations accurate locations might be
useful, especially if two separated cameras happen to catch the same
meteor, a very unlikely occurrence). Also, specify where the telescope
was pointed, at least approximately (alt. and azimuth, or RA and Dec,
and whether driven or not). If you know that you caught one or more
meteors, it would be helpful to give the approximate time, but that is
not necessary; tell whether you have viewed the tape or not (viewing is
not ncessary). Specify whether the telescope was clock-driven or not
(doesn't need to be), and the start and stop times of the recording.
Include your address, telephone number(s), and e-mail address (if you
have one) in the report that you enclose with the tape.
Since accurate pointing is not necessary, the telescope and equipment
can be left mainly unattended while the video records; you just need to
be there to note the end time of a recording and change tapes. For
observation periods like this that are much longer than for
occultations, you need to be sure adequate power and blank tapes are
available. Also, you need to try to prevent dewing using dew caps
and/or heating elements (and then, more power needed).
________________________________________________________________________
2. It has been suggested that observers watch the dark side of the Moon
for large Leonid impacts (see, for example,
http://www.earthchangestv.com/comets/). Last year, there were some
Leonids as bright as the full Moon, which I figure at the 4000 times
greater distance might show up around 4th mag. on the dark side of the
Moon, although the dynamics of a lunar impact would certainly be
different than one in the Earth's atmosphere. Maybe a lunar impact,
being quicker, might even be brighter, so that events on Earth of -2 to
- -4 mag. might even show up on the Moon around 7th or 8th mag., which
would be within reach of many occultation video systems. So maybe in
this way, we could detect the Leonid peak from the Americas, since the
expected peak is around 2h U.T. of Nov. 18 U.T., during the evening of
the 17th local time when the Moon will be well-positioned for observing
from the Americas and 67% sunlit (or 1/3rd of its disk dark). This
would mean observing ALL night, first the Moon, then after midnight the
sky, for meteors. But the good Leonid opportunities only come every 33
years, so I think it is worth it.
All you need to do is image the dark side of the Moon, excluding all,
or as much as possible, of the sunlit side as you can, very similar to
recording an occultation. To avoid duplication and observational bias,
if your system can not cover the entire dark side (few can), then you
should image the northern third (or sector) of the dark side (cusp angle
0N to 60N) if your family name starts with A to H, the central (or
equatorial) third of it (cusp angle 60N to 60S) if your family name
starts with I to P, and the southern third (cusp angle 60S to 0S) if
your family name starts with Q to Z. If your system FOV is
significantly less than 10' so you can't image a whole third of the dark
side, try to observe a part of the sector closer to the north side of
the sector if your last name starts with a letter closer to the lower
end of the alphabetic range for your sector. As far as I know, a meteor
striking the Moon has never been recorded before. If you make a
recording of the dark side of the Moon, send me a message giving the
location from which you observed, the start and end times of your tape,
the approximate FOV, its location (approximate cusp angles covered), and
an estimate of your limiting magnitude on the dark side (the occultation
stars mentioned below might help), and if you noticed any lunar meteor
impacts or not. If so, give their approximate brightness, time, and, if
possible, an estimate of their location (you may need to image a tiny
bit of the terminator to be able to tell the location, since most
systems will not be able to image features on the dark side illuminated
by feeble Earthshine; if you image the terminator, you might do that
only briefly every 5 to 10 minutes by moving the telescope smoothly in
R.A., just to establish your viewing area). If positive observations
are made, we will want to collect the tapes so that the impact locations
can be measured and correlated with others, and we'll ask others to
examine their tapes at the appropriate times. But we'll work out the
proceedures for that ONLY IF we positive observations are obtained.
See the remarks about observing at the top of item 1. above, since they
will apply if there is success and we want to scan your tape.
Of course, as long as you are imaging the dark side, you may as well
try to record some occultations of stars. Perhaps the brightest to be
occulted will be 4th-mag. psi1 Aquarii (= ZC 3419) before and after 4h
U.T. of the 18th U.T. visible from most of the western and north-central
USA and western Canada. For example, in Los Angeles, the star will
disappear at 3:57 U.T. (7:57 pm PST) at a cusp angle of 36S. Times for
many dozen other cities will soon be posted on IOTA's Web page at
http://www.lunar-occultations.com/iota
A good grazing occultation will occur along the southern limit of the
occultation, passing just north of Yuma and south of Flagstaff, Arizona;
south of Colorado Springs; just south of Sioux Falls, Iowa and
Minneapolis; and very close to Sault Ste. Marie. This limit is shown as
line 203 on p. 153 of the RASC Observer's Handbook, that map also being
found at the IOTA Web site given above. Another southern-limit graze
path, of 7.0-mag. ZC 3409 around 2h U.T. of the 18th U.T., passes near
Fresno, Calif.; Brigham City, Utah; and Winnipeg, Manitoba; it is path
202 on the RASC Handbook map. Also, some 7th and 8th-mag. stars will be
occulted; times for two locations are given below. Many of you have
your own predictions for your station. C.A. is cusp angle. Those with
U.T. 23h are Nov. 17th U.T.; other hours are of Nov. 18th, and all
events are during the evening of the 17th local time:
Washington, D.C. Los Angeles, Calif.
Star mag. U.T. C.A. Star mag. U.T. C.A.
h m h m
SAO 146590* 7.1 23:13 14N SAO 146570* 7.8 2:51 25N
SAO 146518 8.3 23:29 78N SAO 146578* 8.2 2:51 56N
SAO 146570* 7.8 3:35 81N SAO 146577* 7.6 2:53 55N
SAO 146577* 7.6 3:55 79S psi1 Agr. 4.5 3:57 36S
*star probably double, expect disappearance in steps.
________________________________________________________________________
3. The Earth will pass only 0.0115 A.U. from the orbit of Comet LINEAR
(C/1999 J3) at 19:41 U.T. of November 11th, U.T., 40 days after the
comet itself was in that area. The geometry is rather similar to that
for Comet Giacobini-Zinner when it produced Giacobinid storms in 1933
and 1985. But Comet G-Z is a short-period (6 years) comet, while Comet
LINEAR is expected to be relatively fresh with a period of about 63,000
years. So it is not obvious that there will be any "Linearids", but it
is certainly worth looking for them. The radiant is in the bowl of the
Big Dipper, near Phecda, at R.A. 11h 40m, Dec. +53 deg. Asia is favored
for seeing LINEAR meteors at the time of closest approach, but the
International Meteor Organization is calling for a watch during the 48
hours surrounding the time of closest approach given above (that is,
from 19:41 UT of Nov. 10 to 19:41 UT Nov. 12). More information is at
http://science.nasadot gov/newhome/headlines/ast05nov99_1.htm
If there is a significant shower of Linearids, we may as well use them
to practice for the Leonids. The Moon will be near new, so it won't be
possible to see Linearids striking the Moon.
David Dunham, IOTA, 1999 November 9
Joan and David Dunham
7006 Megan Lane
Greenbelt, MD 20770
(301) 474-4722
dunham@erols.com
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