In a message dated 6/2/00 7:09:28 PM Eastern Daylight Time, molczan@home.com writes: > The strategy is to use a stopwatch referenced to an accurate time source, > such > as WWV. WWV broadcasts on several shortwave frequencies, including: 5 MHz, > 10 > MHz, 15 MHz, 20 MHz; or you can hear it by phoning 303-499-7111. There are some good time links at: http://www.eecis.udel.edu/~mills/ntp/test.htm (Ted, you didn't mention the Canadian SW broadcast - CHU. That was the only SW station that I could hear duting the aurora a few months ago) > My $30 Casio wristwatch has a stopwatch function with a memory that can > record 30 split times. I'm using the Ultrak 499 ~$59US (at stopwatches.com) and the $25US SW/HW package that allows d/l of the data. I probably don't need the 500 lap memory but it does come in handy when timing the BWGS flashers - particularly the one with strange secondary flashes. > Shortly before I go out to observe, I start the stopwatch. Then I phone the > WWV number, and record several splits at one minute intervals. Is there an advantage to a telephone connection vs SW signal? > I write down the actual UTC time of each split, so that I have a way to > relate > the elapsed time of the stopwatch to UTC. > > If I am reasonably alert, I should be able to consistently hit the stopwatch > to > within a range of a few hundredths of one second. > > I do not take the splits at the start of a minute, because WWV has a several > second pause with no clock ticks prior to the long tone at the start of the > minute. Actually it is only silent for seconds #29 and #59 every minute. The announcement kicks in just before second #53. I generally set my wristwatch ($20 Casio) to the WWV beep a minute or 2 prior to starting the stopwatch. I can anticipate the zero-second beep (minute beep?) better that way. BTW - the GPS that I am using is consistently 1 second behind WWV. Go figure. > Instead, I count off 5 seconds after the minute, and then take a > split. > This should reduce the reaction-time error, but I can anticipate each tick > of > the clock. > > By this process, I have in effect calibrated the start time of the stopwatch. Basically the reaction time error + the start time error is corrected by this click - right? > I may do this calibration as a safety measure, in case I > should > accidentally stop the watch after I have recorded a few positions (it is all > too easy to do that in the dark). Having done the pre-observation > calibration > means that even if I stop the watch, I can still compute the UTC time of > each > split that I have recorded. Without the calibration, the data would be lost. What's really fun is when you have 100+ splits, drop the stopwatch and the whole thing resets. I needed to recalibrate myself by counting to 10. That aside - another good feature of the Ultrak 499 is that you are able to start another group of times. IOW if you stop the time by hitting the wrong button, you clear the time (the splits are still stored in memory) and restart (+ recalibrate) at another known time. Cheers Don Gardner 39.1799 N, 76.8406 W, 100m ASL Homepage: http://hometown.aol.com/mir16609/ ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Fri Jun 02 2000 - 19:00:16 PDT