Very nice John! I'm curious as to what mapping program you use... I've also been very impressed with the aerial color photos that are available to you. In the U.S., generally all that's freely available are B&W USGS photos, such as this of my digs: http://terraserver.microsoft.com/image.aspx?t=1&s=10&x=2096&y=19320&z=17&w=2 I'm about centered in the photo- my neighbor 2 houses to the north (up) has a swimming pool in his back yard, that's evident as a black rectangular, bordered by white. A somewhat interesting website that also displays USGS aerial photos of the U.S. is this: http://www.terrafly.com I've been replacing old wooden windows with hi-tech vinyl ones, and I've got 3 more to go, so now that the rain from Hurricane Charlie has ended (not much of an effect, where I am), I guess I need to get at it. It would be helpful to me, for later analysis, if you included a couple of my ground track points, on either side of your obs point. A------- B----- C----- D--- E----- F--- G------- H-------- I---- 3.3 N 14 Aug 103153 39.1 124.3 341 53.4324 -3.1221 2.0 5.3 NE 14 Aug 103154 39.2 124.4 340 53.4450 -3.0081 2.0 Using decimal notation, your location was 53.4380° N, 3.0639° W, and according to my track, the ISS should have passed the center of the Sun at about 10:31:53 + (3.0639 - 3.0081) / (3.1221 - 3.0081) = 10:31:53 + 0.0558 / 0.1140 = 10:31:53.49 I didn't digitally dissect your gif, but just eyeballing it, that appears to be about 0.5 sec early (factoring in 235 msec latency for your webcam). The MCC TLEs apparently are computed to allow the simplifying assumption that UT1 - UTC = 0.00 (UT1 supposedly is the proper time to use in the SGP4 computation), and (coincidentally or not) UTC is currently leading UT1 by about 0.5 seconds: ftp://maia.usno.navy.mil/ser7/ser7.dat http://tycho.usno.navy.mil/systime.html http://www.boulder.nist.gov/timefreq/pubs/bulletin/leapsecond.htm http://home.tiscali.se/pausch/comp/time.html The day-of-year time was 227.397153, and the nearest MCC TLEs would have been: 1 25544U 98067A 04226.42819699 .00020000 00000-0 20000-3 0 9012 2 25544 51.6324 33.5657 0005255 107.0130 253.1608 15.70811150 7316 1 25544U 98067A 04227.44609185 .00020000 00000-0 20000-3 0 9023 2 25544 51.6314 28.3608 0005243 110.3838 249.7887 15.70791748 7479 (My prediction actually would have used the first one.) OIG reports: 1 25544U 98067A 04227.08328711 .00017992 00000-0 14584-3 0 4409 2 25544 51.6326 30.2103 0005561 113.4008 353.7675 15.70830660327417 1 25544U 98067A 04227.53163875 .00018164 00000-0 14708-3 0 4418 2 25544 51.6324 27.9180 0005523 115.2669 9.0526 15.70848506327485 I recently received some information from Jon Weaver at the MCC, who's responsible for the software that computes the MCC TLEs. Aside from indicating that these TLEs assume True Equator / Mean Equinox (per SGP4 gospel), he had some other interesting information, in reply to one of my questions: "What drives the" (usually) "Monday and Thursday updates is the ISS Trajectory Flight Controllers receive updated Orbit Determination vectors. The source of these is either the Russians or USSTRATCOM. They then anchor their ephemeredes on these fresh OD vectors and the ephemeris accuracy hangs in good enough 'operations-wise' such that two updates a week are sufficient. "Special updates occur when the vehicles dock with the ISS (which makes minor perturbations to the orbit), when ISS performs orbit adjust or collision avoidance maneuvers, etc." ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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