Good Lunar Leonid Opportunity This Weekend
Updated: 2001 Nov. 151. This weekend's Leonids opportunity could be the best chance in our lifetimes to observe lunar meteor impacts. 2. The Watec 902H camera is highly recommended for recording lunar meteor impacts, and experience has shown it also GREATLY aids videorecording lunar and asteroidal occultations. _________________________________________________________________ 1. This coming weekend's Leonids meteor shower may present the best chance to record lunar meteor impacts in our lifetime, since planetary perturbations are expected to move the Leonid streams away from the Earth and Moon during the next two Leonid opportunities around 2033 and 2066. Detailed information is given by Brian Cudnik at the ALPO Lunar Section lunar impacts web site at http://www.lpl.arizona.edu/~rhill/alpo/lunarstuff/lunimpacts.html At that site, read the top and click on the large type "Lunar Impact Alert Notice!" that has the direct link http://www.lpl.arizona.edu/~rhill/alpo/lunarstuff/impactalert.html that includes a diagram from Armagh Obs. showing the predicted paths of the Earth and Moon through the Leonid streams. It indicates passages of the Moon through streams on Nov. 17 around 15h UT and again (3 or more streams) on Nov. 18 from 12h to 19h UT. The Moon will be a thin waxing crescent in the southwest. With the Moon's southern declination, it will stay higher in a dark sky for southern observers, and at the times above, observers in South Africa and western Australia will have the best views. But opportunities are also good farther north, from Europe and most of Asia on Nov. 18 UT, and more around the Middle East on Nov. 17th. Of course, there should be some increased activity inbetween, so even observers in the Americas are encouraged to observe from when it gets a little dark after sunset for as long as possible before moonset especially the evening of Nov. 17th local time, and also the evening of Nov. 18th local time. But Americans are very unlikely to have activity as high as occurred on 1999 Nov. 18. This will be offset by the fact that the Moon will be a thin crescent this time, with much less lunar glare, allowing imaging the fainter impacts that were more difficult with the gibbous Moon in 1999. Also, locating the impacts will be much easier this year since the maria and other lunar features will be strongly illuminated by Earthshine. There are few lunar occultations these evenings, and the ones that occur are very localized, so we won't try to give predictions of them. If you videorecord the dark side of the Moon for lunar impacts, be sure to videorecord at least a couple of stars nearby so that the brightness of any impacts that you record can be measured. This year, observers need to concentrate on the central part of the Moon, the area on the dark side closer to the terminator, rather than near the dark edge, since no Leonids will fall on the third of the Moon closest to the dark edge. This is shown in the diagram for the Leonids on the first ALPO Web site noted above, where you need to click on the item called "THE LUNAR IMPACT PLOTS". This is long, with plots for many minor meteor showers; the one for the Leonids is about 4/5ths of the way from the top to the bottom. I will try to isolate the diagram for the Nov. 17-18 Leonids and place it on the lunar meteor impacts section of http://iota.jhuapl.edu later this week. _________________________________________________________________ 2. If you act quickly, you might be able to upgrade your capabilies for recording lunar Leonids, and later, all occultations. The Watec 902H camera is highly recommended for recording lunar meteor impacts. Last night, I used it for the first time to image the 10% sunlit Moon's dark side, recording 4 reappearances of stars. It was fantastic, with incredible detail visible on the Earthlit dark side, and the 9th-mag. stars showing brilliantly, using my 8-inch Schmidt-Cass. and f6.3 focal reducing lens. The Watec camera will clearly be able to record lunar impacts about 2 magnitudes fainter than the PC-23C, and similar gains are obvious for lunar and asteroidal occultations as well. It has almost the same performance as my image-intensified system at a fraction of the cost; I bought my Watec 902H from Security Products International, Pottstown, PA (phone 610-970-5150) for $340 + $6.63 for shipping, but lower costs may be available elsewhere - see the end of this message, which also has some more information about operating the camera. The Watec 902H camera is made in Japan and widely used by observers there. Contact information is available at http://www.watec.com but that is for the American division in Las Vegas; you can e-mail them at watec@watec.com to perhaps ask them about dealers selling the camera in other countries (you might also check with security camera and telescope dealers in your country). With my telescope, it will make it possible to observe grazes of 9th and probably even 10th-mag. stars during the crescent phases, giving more opportunities to observe these events closer to home. It is also HIGHLY recommended for asteroidal occultations, making it possible to videorecord many more of these events than with the PC- 23C. Visual observations of asteroidal occultations, especially of fainter stars, suffer greatly from always larger-than-reported reaction times which always complicates the analysis of those events; removing the "personal equation" greatly increases the value of those observations. The larger area as well as the sensitivity helps considerably in finding the target star. Visual observations of asteroidal occultations are not useless, and are encouraged at least to help define the path limits, but video timings are better. Also useful, if you have a Schmidt-Cass. telescope, for inceasing the area of the Moon imaged, is a focal-reducing lens; this also helps for asteroidal occultations (larger field of view) and lunar occultation reappearances. The f6.3 focal reducer is available in the range of $125 to $140 or so from many telescope dealers. Probably even better, for a larger field of view to image virtually all of the Moon's dark side, is the Meade Series 4000 CCD f3.3 focal reducer available for $144.95 from Focus Camera, Inc. in Brooklyn, NY (phone orders 888-221-0828), and probably from some other Meade dealers. I just received mine today, and it fits my C-8 since Meade and Celestron backs are the same. I hope to try it out tonight and will send another message only if I have any problems with it. As mentioned in my message in early August, the Watec 902H is very small (32mm on a side) and operates essentially the same way as the common Supercircuits PC-23C (but it has just an RCA output rather than BNC video output, so you don't need a BNC-to-RCA adaptor) and is powered the same way, with 12V DC, with the same power cord available from Radio Shack - see details in the video information on the IOTA Web site at http://www.lunar-occultations.com/iota Don't through away your PC-23C since it's handy as a microphone/mixer to record sound (WWV); the Watec doesn't have a microphone. Frank Anet writes, and I concur (and add some more information): The standard high sensitivity setting on the WAT-902H is useless, as the noise background is very high, greatly reducing the dynamic range, and the sensitivity is no better than with the low setting. The cover on the back of the camera needs to be removed (micro-size Phillips screws) to get to the ultra-micro switch to change the sensitivity to low (the camera is extremely small and light weight). On the low setting, the background noise for a dark scene is still greater than necessary (but much reduced from the high setting and certainly acceptable). I permanently set the sensitivity to low. When observing lunar occultations, it behaves in the same way as does the PC23C, so that the gain is reduced automatically if too much of the bright side of the moon is visible (or also if there is a lot of glare from the invisible bright limb). Like the PC23C, it has a switch to control the exposure time (either 1/60 second or automatic). For dark images, these two settings give the same results. The sensitivity is adjusted from high to low with a microswitch that can be reached only by taking off the back plate of the camera. Frank recommends a No. 00 Phillips screwdriver to remove these small screws; the screwdriver available in the "Radio Shack" kit works, according to one source. But I was able to remove the screws with a No. 0 Phillips screwdriver. With the back removed, the tiny white sensitivity microswitch (not labelled) is mounted on the right side of the right side card (looking down into the camera with the RCA video output jack up), about a 4th the size of the shutter on/off switch on the left side that is accessible through a hole in the back plate. The sensitivity microswitch comes in the up (high sensitivity) position; just use a small object, or your fingernail, to push it down). Then reattach the back plate (last night, I observed without the back plate on, wanting to know what would happen when I changed from high to low sensitivity, but after seeing the results, the much higher noise with high sensitivity, I'm going to keep it on the low setting). More about sources for the Watec 902H: Tony Cook wrote in Aug.: As for prices - I hunted around on the web. The price for the 902HS at the following site is claimed to be $350 but when I phoned up and asked they gave me a price of $320? and the 902H was under $300. (the 902H is recommended; tests show that the 902HS is noisier, but not really more sensitive for detecting stars, than the 902H). http://www.4spi.com/pages/pg1.html [this is the route I followed, but the "under $300" price doesn't seem to be available now. David] Frank Anet wrote earlier: I purchased a Watec video camera (WAT-902H) from Rock House Products International, 2 Low Avenue, Suite 205, Middletown, New York 10940, because of its "Ultra Low Light" ability and "Incredible Low Light Operation", as quoted on the Rock2000.com web site. The price was about $500, but that was several months ago; it is probably cheaper there now. _________________________________________________________________ David Dunham, IOTA, 2001 Nov. 15