Let's Try to record Geminids - Dec. 10
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 At this site click on "sights", then in the left menu on "meteors", and about 3/4th of the way down that item, on "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/iotandx.htm 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 13 7006 Megan Lane Greenbelt, MD 20770 (301) 474-4722 dunham@erols.com