First Announcement of Other Confirmations - Nov. 23-24
Pedro Valdes Sada reports two lunar flashes that he videorecorded near Monterrey, Mexico, about half an hour after the event seen by Brian Cudnik and recorded by me that is now so famous. He gives the times in his message, copied below. They are also on my tape, made in Mount Airy, Maryland, at the times he gives! Later today, we will digitize these two new flashes and put them up at http://iota.jhuapl.edu They are also near the lunar equator. We will be determining the exact times from the tapes when we can; I'm sure they will agree to within the 1/15th or so second of timing that we can probably recover from the tapes. I had a WWV minute tone recorded at 5:07:00 UT, 7 and 8 minutes before the flashes, respectively. The new objects are also probably Leonids, since it was still near the time the peak was striking the Moon, but of course we do not know for sure, since we don't know from which direction the meteoroids approached the Moon. For observers, a key to my success in this endeavor was the focal reducing lens that I purchased from Orion; it decreased the f-ratio of my 5-inch Schmidt-Cassegrain telescope from 10 to 6.3. That not only increases the field of view by more than a factor of 3 in area, but also increased sensitivity by concentrating the seeing disk of point sources onto fewer pixels, and allowed, for example, recording (faintly) the Earthlit dark side of the Moon. By measuring images showing the lunar cusps and terminator taken before and after the 4:46:15 UT event, I was able to determine that it occurred at an angle (measured from the Moon's center, called "cusp angle" in occultation terminology) of 77 deg. from the north cusp. Using also the distance of 1.7' in from the edge, this puts the impact point in Oceanus Procellarum (Ocean of Storms) about 50 km east-northeast of the center of the 50-km crater Cardanus, at selenographic longitude 71 deg. W., latitude 14 deg. N., with estimated accuracy of 2 deg. or 50 km. David Dunham, IOTA, 1999 Nov 23
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 SchiaparelliMag1 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.
David Dunham, IOTA, 1999 November 24