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(meteorobs) Two more confirmed lunar impacts - now 5



In a message dated 11/24/99 1:00:18 PM Eastern Standard Time, 
dunham@erols.com writes:

> David Palmer reports two more lunar impacts that he 
>  videorecorded at his home in Greenbelt, Maryland at 3:49:41 and 
>  4:08:00 UT of 1999 November 18.  The times are estimated to be 
>  accurate to +/-3 seconds since they were obtained just by 
>  calibrating the VCR clock with time from the CNN cable TV broadcast. 
>  The flashes are also in the video recording that I made at Mount 
>  Airy, about 60 km to the northwest, bringing the total now to five 
>  confirmed lunar impacts, four of them on my tape and also on other 
>  videotapes made by others, and the other, the first one reported, 
>  confirmed with Brian Cudnik's timed visual observation. 
>  
>       Brian Cudnik reports that the flash he saw was yellowish-orange 
>  in color, redder than nearby psi1 Aquarii.  All of the 
>  videorecordings are black-and-white.  A third probable untimed 
>  visual confirmation of that event has been provided by Steve 
>  Hendrix, who watched the dark side of the Moon with a 4.5-inch Meade 
>  telescope from Cameron, Missouri from 4:40 to about 4:55 UT.  It was 
>  the only flash that he saw during that period and it matched Brian 
>  Cudnik's description.  Before hearing about Cudnik's and my 
>  description of the flash, Hendrix was hesitant to share his 
>  observation since he had "never seen anything like this before and 
>  didn't want to appear over zealous".
>  
>       A summary of the five confirmed lunar impacts are given in the 
>  table below.  This is an ASCII plain text table that must be viewed 
>  with a fixed-space font such as Courier for the columns to line up 
>  properly.  For the time being, we are naming these with letters in 
>  the order of discovery.  The UT date is 1999 November 18.  In each 
>  case, the events were confirmed on my videotape made at George 
>  Varros' backyard in Mount Airy, Maryland, and the timings are from 
>  my tape.
>  
>             Accuracy, Approx.  Discovered  Selenographic
>  Name  U.T.    sec. Mag1  Mag2    by       Long. Lat. Description
>     h  m   s
>  D  3:49:40.5   0.4   3    7  David Palmer  48W   1N 175km SW of Kepler
>  E  4:08:04.1   0.6   5    8  David Palmer  70W  15S 175km S of Grimaldi
>  A  4:46:15.2   0.1   3    8  Brian Cudnik  71W  14N  50km ENE of Cardanus
>  B  5:14:12.93  0.05  7    8  Pedro Sada    58W  15N 200km WNW of Marius
>  C  5:15:20.23  0.05  4    7  Pedro Sada    59W  21N  75km S Schiaparelli 
>  
>  Mag1 is the approximate magnitude of the flash estimated from my tape on 
>  the half-frame on which it first appears.  Mag2 is the estimated 
>  magnitude a half-frame, or 1/60th second, later.  In all cases except D 
>  I can't see any evidence of the flash in the half-frame 1/30th second 
>  after the first one, except for D, where it seems to appear there at 
>  about 9th mag. The selenographic locations for D and E are very 
>  approximate, based on rough estimates rather than measurements, and 
>  could be in error by 5 deg. or more.  The others should be accurate to 
>  within about 2 deg. or 50 km.  All of these are in the western part of 
>  Oceanus Procellarum (Ocean of Storms) except E, which is in highlands 
>  area a short distance west of the western shore of Oceanus Procellarum. 
>  The times of B and C have been determined by Don Stockbauer, Victoria, 
>  Texas, after creating an accurately time-inserted copy using an IOTA-
>  Manly video time inserter.  He also determined the time of A, but for 
>  technical reasons to less accuracy; it will be possible to refine it 
>  later.  D and E have been timed from the tape just using a stopwatch. 
>  
>       Several have asked me how large the impacting meteors are, and if the 
>  new crater they form might be seen.  I need help from an expert in impact 
>  dynamics on this - I don't have expertise in that field.  I have heard one 
>  estimate that the impactors, to produce flashes this bright, are meter-
>  size, but another estimate is that they may be just 100 grams or so.  In 
>  any case, I believe that the "splash" that these objects made are less 
>  than 100m across and will not be visible with Earth-based telescopes.  In 
>  2003, the Japanese Selene spacecraft plans to map the Moon from low orbit 
>  in detail, and coparison of its images with those of Lunar Orbiter, 
>  Apollo, and/or Clementine will hopefully reveal some small new craters.
>  
>       Ray Sterner and I digitized our images of B and C yesterday and we 
>  hoped to get them posted on our Web site at http://iota.jhuapldot edu, but 
>  that might not be possible now until Monday.  In the meantime, we will 
>  post the latest information about these flashes at the main IOTA site at 
>  http://www.lunar-occultations.com/iota
>  including Sada's images of B and C, and Palmer's images of D and E.
>  I don't plan to make any more mass-mailings like this one about these 
>  events, but will distribute future updates to a few who are especially 
>  interested.  Otherwise, check the Web site for further updates, but I will 
>  try to answer specific questions about these events.
>  
>  David Dunham, IOTA, 1999 November 24
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