From: Andrew Scheck [Andrew.Scheck@jhuapl.edu] Sent: Thursday, October 18, 2007 4:55 PM To: Dunham, David Subject: Re: Your ZC 2702 observation from northwest Laurel Telescope info: size 8", f/10, Celestron NexStar 8 GPS, clock-driven Andy On Oct 18, 2007, at 02:37 PM, Dunham, David wrote: Andrew, Many thanks for your observation. It's valuable because of the relatively short events that you had; your location was higher on the lunar profile than any of the other observers, so it provides unique information to help map the profile. I'm copying this to Dale Lehman who conducted his own one-man expedition to northeastern Columbia to observe the occultation from a location that was between yours and our locations on the profile, since he had only a single 2-minute occultation. Using www.topozone.com, I determined your height above sea level to be 400 feet (the ground elevation was a little lower, but I assume your scope was on a tripod a little above ground level; also, the topo map used at that Web site did not show the housing development that you currently live in, so there may be a small elevation change from whatever grading the developer did during the construction, but that would probably not be significant; in the plans for the development, there may be drawings showing both the original and current elevation contours, but we only need an accuracy of 10m). Our official report for the graze also wants the size, focal length, and type of your telescope, and whether it was manually guided or clock-driven (as are GoTo telescopes). Unfortunately, we ran out of time at our own expedition. Before our meeting at 7 pm, I managed to set up three telescopes at hidden locations north and south of the high school. After getting a couple of others with independent capability squared away to set up at locations at opposite ends of the high school, and setting up a 4th telescope to show what to do for the other helpers (and keeping that in my car, intending to use it myself at the last minute from a location not far from one of the others), we went to each of the 3 pre-set-up telescopes to point them at the star and attach recorders to them. By the time we got the last of the 3 up and running, located in a field behind some trees about 100 feet from the nearest parking place, the graze had just started, so I didn't have a chance to use the 4th telescope at a location next to my minivan where I could record WTOP. So unfortunately, I didn't get the WTOP recording. I should have delegated that job to someone else. I'm copying this to Bart Huxtable who observed at the school and was planning to use WTOP as the time base, but I gave him a WWVB-self- setting alarm clock to use for timing. I don't know if he recorded WTOP and the alarm, or only the alarm. If he did the former, then we can use his tape to calibrate yours; I did record the alarm clock he used after the graze to calibrate it, in case there's any offset of it relative to UTC determined from GPS. If he didn't record WTOP, we'll use the WTOP 8 pm hour tone (lucky the graze period included that), and in any case, I'll check a couple of WTOP's hour tones tonight. If they're not accurate, I'll contact WTOP to see if they have a record of the timing of last night's broadcast; some stations keep such a record, at least for a few days. David ____________________________ Later, I learned that Kevin Hartness recorded WWV and WTOP, creating a useful calibration tape. Bart Huxtable also recorded WTOP and the alarm from a WWVB-self-setting clock that I in turn calibrated with GPS after the event. -------------------------------------------------------------------------------- From: Andrew Scheck [mailto:Andrew.Scheck@jhuapl.edu] Sent: Thursday, October 18, 2007 9:01 AM To: Dunham, David Subject: Re: So far, staying clear for tonight's good graze; I could use your help near Atholton H.S. or elsewhere Dave, I think I was successful last night; unfortunately I was about 3 mi south of your location so maybe this isn't as useful as it could have been. I'm including what I got: mp3 of my "on" & "off" events with WTOP recorded in the background Google Earth location notes indicating where in the audio to look for my events Date: 10/17/2007 Time: ~ 7:57:26 through 8:00:06 (if WTOP's 8:00 *beep* is accurate) Location (from Google Earth image) Lat: 39.149419144668 Lon: -76.887334650749 WTOP recorded in background. Approximate times (from recording beginning) for important(?) events. 00:00 (start recording) 00:04 (my voice) "still on" 00:12 (my voice) "off" 00:32 (my voice) "on" 00:51 (my voice) "off" 01:58 (my voice) "on" 02:34 (WTOP radio) "It's 8:00 *beep*" 02:40 (end of recording) Note: I recorded over 16 minutes but trimmed to just this section as it spanned everything that I thought was important. I have the whole thing if you need it.