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(meteorobs) Saturn occ'n Dec. 2/3; Leonids & Geminids, etc.
------- Forwarded Message
Date: Wed, 01 Dec 1999 03:05:51 -0500
To: webmaster@lunar-occultations.com
From: Joan and David Dunham <dunham@erols.com>
Subject: Saturn occ'n Dec. 2/3; Leonids & Geminids, etc.
More information is given below about:
1. Occ'n of 9.2-mag. SAO 93040 by Saturn throughout Americas Thurs.night
2. Telescopic videos from Nov. 16-18 wanted for meteor studies
3. Lunar Leonid news - now 6 confirmed; obs. info. wanted, other news
4. Let's try to record lunar Geminids
5. Next camcorder occultation - Jan. 2nd am & 9th pm, best in East
6. Next Mid-Atlantic graze expedition - Jan. 1st near Richmond
_______________________________________________________________________
1. Occultation of SAO 93040 by Saturn throughout Americas Dec. 2/3
The 9.2-mag. star SAO 93040 = PPM 118428 will be occulted by Saturn
and its rings for observers throughout the Americas from just before 4h
UT to shortly after 6:30 UT of December 3, UT. The disappearance can
also be seen from the Canary Islands and the reappearance will be
visible from Hawaii. The star will disappear behind the ball of Saturn
near the South Pole around 3:50 UT and will reappear almost 80 minutes
later. Then for the next 1.5 hours, the star will pass behind Saturn's
B ring, then its A ring. It will be visible in Cassini's Division for
at least a few minutes around 6:10 UT. For observers in Puerto Rico,
Cuba, Guatemala, and southernmost Mexico, the star will "graze"
Cassini's Division, staying visible in it for almost an hour! For
observers in South America, the star will pass entirely south of
Cassini's Division, avoiding it and the B ring. The southern limit will
not cross Ecuador and the Amazon Basin, as stated in my article on p.
108 of last February's Sky and Telescope, but instead lies near Tierra
del Fuego. Predictions of the occultation for many locations, including
a view of the star behind the planet, can be found at Doug Mink's
planetary occultation Web sit at http://tde-www.harvarddot edu/occultations
This would be a much more interesting event if the star were
brighter. But because Saturn's surface brightness is 7th mag. per
square arc second, actual occultation events will be extremely hard to
see or record unless one can decrease the planet's brightness relative
to the star by observing, for example, in the methane absorption band
around 8900 Angstroms.
_______________________________________________________________________
2. Telescopic videos from Nov. 16-18 wanted for meteor studies
As mentioned in my message of November 9th, telescopic video
observations of Leonids in Earth's atmosphere are sought, with and
without image-intensified systems. Observations are sought from 0h UT
November 17 to 0h UT November 19. Dr. Bob Hawkes of Mount Allison
University, New Brunswick, claimed to have seen "jets" protruding
perpendicular to several Leonid tracks in last year's videos. The
physical phenomena is unknown at this time. If you made any such
recordings, please send them to:
Peter S. Gural
Science Applications International Corp. (SAIC)
4001 N. Fairfax Drive, Suite 400
Arlington, VA 22203
Phone +1-703-816-5954
He will have the tape digitized and computer-searched for meteors; you
don't have to view your tape to tell if there are any meteors in it or
not. Specify your observing location, preferably including longitude,
latitude, and height above sealevel (don't need to be as precise as for
occultations). Also, specify where the telescope was pointed, at least
approximately (alt. and azimuth, or RA and Dec, and whether driven or
not). Some of us started our tapes pointed at a bright star, then
didn't use a clock drive to just let it drift out of the field of view;
if you did this, just identify the star. Specify 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.
_______________________________________________________________________
3. Lunar Leonid news - now 6 confirmed; obs. info. wanted, other news
The first 5 confirmed lunar impacts were described in I.A.U.
Circular 7320 issued on Nov. 27th. It included David Asher's prediction
that the Moon passed much closer to the core of the 1899 Leonid stream
around 4:49 UT than the Earth did around 2:08 UT, causing a storm on the
Moon comparable to what the Earth experienced in 1966, so the impacts
that we recorded around that time are most likely due to Leonids.
If you made any video recordings of the Moon's dark side between 0h
UT November 17 and 0h UT November 19, or even watched it visually during
these times, please send me a message stating the telescope and camera
used, the estimated limiting magnitude, the start and stop times of the
tape (or observation), how the observations were timed, whether or not
the earthlit dark edge is visible, the approximate field of view size,
and whether you predominantly recorded the central, northern, or
southern part of the Moon's dark side. Also useful to know for
calibration is whether or not you imaged any stars or recorded any
occultation disappearances. We are working on ways to digitize the
tapes and search them with software to find impacts. Once we work out
the procedures, we will ask for the tapes, but for now, keep your
original tapes.
Besides the 5 confirmed lunar impacts that were tabulated in a
message a few days ago, a 6th has been confirmed, impact F, recorded by
both David Palmer and I at 3:05:44 UT November 18. Besides this and the
other known impacts, please check your tape at the following times when
flashes were recorded that have not yet been confirmed:
UT Nov. 18 Observer Remarks
2:40:04 David Palmer might be a tape defect
4:32:50.8 Pedro Sada n. of equator; Dunham had nothing recording s.
4:34:49.7 Pedro Sada n. of equator; Dunham had nothing recording s.
4:50:15.9 David Dunham visible in only one half-frame
These are around 4th mag., 5th mag. for Sada's events. Although impact
A at 4:46:15.2 UT was seen and timed by Brian Cudnik, and apparently
seen but not timed by Steven Hendrix in Cameron, Missouri, mine is the
only known video of the event - if you have a video covering that time,
please check it. Impact D at 3:49:40.5 was recorded by Rick
Frankenberger in San Antonio, Texas, as well as by Sada, Palmer, and me,
quadruply confirming it. Two observers who used large telescopes on
separate nights, one visual on the 18th UT and the other video on the
17th, reported dozens of faint flashes on the Moon's dark side, mostly
around 10th and 11th mag., beyond the reach of the 5 and 8-inch
telescopes used by the observers mentioned above.
There remains considerable uncertainty about the size of the bodies
causing these impacts, with estimates ranging from tens of grams to 20
kilograms, depending on the efficiency with which the large kinetic
energy of these objects (relative velocity 71 km/sec) was converted into
light (from 20%, almost certainly too high, to only 0.1%, which gives
the larger size).
_______________________________________________________________________
4. Let's try to record lunar Geminids
The Geminid meteors are expected to peak around December 13th, with
possibly larger objects predominating after the peak. Although not of
storm caliber like the recent Leonids, the Geminids do have a
respectible rate and include many large meteors. The lunar geometry is
quite favorable this year with the Moon being a waxing crescent. So
wherever you are, I recommend trying to record the dark side of the Moon
as much as possible both the evenings of December 13th and 14th, local
dates. In eastern North America, the Moon will be 30% sunlit on the
13th and 39% sunlit on the 14th. We will place predictions for some
occultations during these nights for at least North American locations
on IOTA's Web site at http://www.lunar-occultations.com/iota
As noted earlier, those using Schmidt-Cassegrain and other long
focal-length telescopes can both enlargen their field of view and
increase sensitivity by using focal-reducing lenses. Wayne Warren
searched different sources for these and found the lowest cost, around
$120, from Adorama.
_______________________________________________________________________
5. Next camcorder occultation - Jan. 2nd am & 9th pm, best in East
Two occultations that can be recorded directly with most
camcorders, without a telescope, will occur early in the new year. On
Sunday morning, Jan. 2, 4.0-mag. gamma Librae will reappear on the dark
side of the 16% sunlit waning Moon between 10:30 and 11:10 UT for most
of the USA east of the Rocky Mountains and Canada east of Manitoba.
Then a week later, late in the afternoon of Jan. 9th, an occultation of
3.0-mag. delta Capricorni will be visible from much of North America,
but after sunset with disappearance on the dark side of the 9% sunlit
waxing crescent primarily in Pennsylvania, New York, New England,
Quebec, and the Atlantic Provinces. Spectacular grazes will be visible
from the southern limits of these occultations, over Lower Matecumbe Key
in Florida on the 2nd and in Pennsylvania (Mercersburg, n. of
Harrisburg, and near Scranton), part of New York, Massachusetts (near
Amherst), and New Hampshire (near Portsmouth) on the 9th. Predicted
times for large North American cities, and a small-scale map showing the
limits, is in my lunar highlights article in the January 2000 issue of
Sky and Telescope, and predictions for dozens of other cities are
available at the IOTA Web site. Also in the Southeastern USA on Monday
morning, Jan. 3rd, will be an interesting occultation reappearance on
the dark side of a thin crescent Moon of the asteroid 4 Vesta; some
predictions for it are on the IOTA Web site. More about these events
will be distributed later.
_______________________________________________________________________
6. Next Mid-Atlantic graze expedition - Jan. 1st near Richmond
For those of you in the Mid-Atlantic States, due to too much other
work, we did not mount an expedition for the graze of an 8th-mag. star
near York, PA on Tues. morning, Nov. 30th, although it was very clear,
and we also will not try the graze of 8.0-mag. SAO 138923 just after 6
am Thursday morning, Dec. 2, near Lewisbury, PA and Newark, DE, by the
26% sunlit waning Moon. If you want to try the Dec. 2nd graze, let me
know and path information can be provided. The next graze that we plan
to try will be the similar graze near Richmond, VA at 4:34 am EST New
Years Day.
_______________________________________________________________________
David Dunham, IOTA, 1999 December 1
Joan and David Dunham
7006 Megan Lane
Greenbelt, MD 20770
(301) 474-4722
dunham@erols.com
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