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(meteorobs) Re; Lunar impacts

David & all,
      Surely the HST could watch the moon for impacts.    Although it is
down to two gyros from six, two should be enough for the
Hubble to get a fix on the moon.

For every lunar impact seen by from the earth, the Hubble would see 100.
As only six were seen during the Leonids, odds on no
Geminid impacts will be seen from the earth, due to ZHR, velocity etc.

    Only reason we might see any Geminid impacts is the mass of eyes
that will now be looking.

    While I like the idea of humans making these discoveries, there is a
lot of science that could be gained with the HST. e.g. viewing a
large range of impacts will help us get a better idea of the sizes of
these objects. etc.

NASA?

Stuart.



Joan and David Dunham wrote:

         First, I apologize to those of you who don't have telescopes;
     I must get this message out quickly and am therefore sending this
     to my ENTIRE mailing list - if you are in this category,
     just delete the message now.
     _________________________________________________________________

         Much good information about observing lunar Geminids has
already
     been posted at http://www.LunarImpact.com NASA Science's Web site,
     which you should visit.  Also useful is the diagram showing the
     expected Geminid rates at
     http://www.skypub.com/sights/meteors/geminids
     Although it shows the situation for 1998, it gives solar longitudes

     at the bottom that can be used to also determine the situation for
     1999.  For 1999, the leftmost part of the chart (solar longitude
     261.2 deg.) occurs at 16h U.T. of Dec. 13.  This indicates that
     the best part of the shower, with rates of 100 or more per hour,
     will occur from about 9h to 21h UT of Dec. 14.  Keeping in mind
     that these are for the Earth, and that the Moon follows the
     Earth around the Sun at this time by about 2 hours, it indicates
     that observers in the Pacific Ocean region, Asia and Australia
     should have the best chances for observing Geminids striking the
     Moon.  But the rates will be about half the maximum or more for a
     longer time, from about 18h U.T. of Dec. 13 to 9h U.T. of Dec. 15,
     so observers are encouraged to observe whenever the Moon is
     reasonably well-placed in a dark sky during this period, roughly
     the evenings of Dec. 13th and 14th local time for most, including
     the Americas.

          The LunarImpact site above lists bright stars near the Moon
     that can be recorded briefly at the beginning of a taping for
     calibration.  Also, a few 7th and 8th magnitude stars will be
     near the Moon at times; every 15 minutes or so examine the space
     ahead of the dark limb to see if any stars are approaching it,
     and record them if you see any, preferably up to the time of
     their occultation.  Predictions for some of these events for
     North America are given at IOTA's Web site at
     http://www.lunar-occultations.com/iota

          Occultation observers and others with telescopes and
     video cameras are encouraged to try to record these events with
     whatever equipment they have.  Even visual observers are not
     discouraged, especially if they can time any flashes they might
     see using a tape recorder or stopwatch and either shortwave
     or accurate telephone (such as the USNO master clock) time
     signals.  If Brian Cudnik had not observed visually on Nov. 18th,
     we might still not know about the lunar Leonids, since most of
     us would not have looked at our lunar tapes closely until
     well afterwards, or in some cases, if ever.

          Video observers should also try to take precautions so
     that any flashes that they observe might be located on the
     Moon's surface, to compare with others to rule out for sure
     the possibility of a sunglint from a very high-altitude
     satellite.  Keep your camera at the same orientation and
     at the start of an observing run, record a little of the
     north and south cusps, and terminator.  Then during the
     observation, try to keep part of the dark edge of the Moon
     in view.  The dark side was hard to detect in most videos
     on Nov. 18th with the Moon over 60% sunlit, but for the
     Geminids, the Earthshine will be brighter and glare from
     the sunlit side less, so most telescopic video systems
     should pick it up.

          The Geminids will strike the Moon with less velocity
     than the Leonids, so their flashes will probably not be
     as bright.  Also, the density of objects is lower.
     Nevertheless, I think it is worth a concerted effort to
     see what might happen.  The Geminid rates raise relatively
     slowly to the broad peak, then fall more rapidly.  However,
     I've heard that the later meteors (those on the evening of
     the 14th local time) tend to be brighter (larger), so
     that might produce more observable flashes on the Moon.

          David Dunham, IOTA, 1999 December 10o
     Joan and David Dunham
     7006 Megan Lane
     Greenbelt, MD 20770
     (301) 474-4722
     dunham@erols.com


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