Thanks all! "Naturally," this morning in South Carolina, it's completely overcast, with a visibility ceiling of about 1300 feet :-( Thunderstorms have been in the forecast about all week, though it was clear for a while yesterday, after sunset. I'd hoped to drive about 150 miles round-trip to Asheville, NC, now that I'm finally setup for video: http://iss-transit.sourceforge.net/firewire-webcam.html Well, that's 5 gallons of gas saved, I guess! For those who didn't know, this (June) month's Sky & Telescope has a one-page article, written by Stuart Goldman, about my ISS Transit email alert service. I've been threatening for a while now to scan it in, and post it on the URL above. Dr. Tony Phillips (better known for his SpaceWeather site) actually contacted me in reference to making a transit map- he's involved with helping 600 5th-grade students in Mississippi, Alabama, Louisiana and Florida to see the ISS, and learn more about astronomy & science. Patrick Wiggins wrote: > Those of us here in the western US have a chance to see ISS "eclipse" Jupiter the next night (the 14th). > Now if only the weather will cooperate. Jupiter "encounters" (my preferred term, which implies 1) that due to the typical accuracy of TLEs, it'll take some luck to actually observe a transit; and 2) it'll also take some luck to capture a frame showing a planetary transit / conjunction / occultation / eclipse by the ISS, unless you have access to a 1000 fps camera, like Roland Stalder) will also be visible in other places. One orbit after the eastern U.S. pass tonight, there will also be a visible pass that will go through areas of the Midwest; and 4 orbits prior to the eastern U.S. pass, Torsten Edelmann may have a shot at it in Germany. http://mysite.freeserve.com/astro2/astro2_image_67.htm http://iss-transit.sourceforge.net/subscribers/RolandStalder.html http://www.wonderplanets.de/latest.html Ron Robisch wrote: > My question then is this: Should I go with the slightly early orbital elements, the slightly later orbital elements, or should I interpolate between the two times, in order to get the most accurate elements for the time of the transit? Just go with your transit reports! If you're not getting them via email for some reason, they're also online at: http://iss-transit.sourceforge.net/transits/matches-840p.txt and http://iss-transit.sourceforge.net/transits/matches-844p.txt Typically, NASA's MCC updates their ISS ephemeris page on Mondays and Thursdays. Assuming that they update it today, I'll generate updated reports. In specific reply to your question, however, use the TLE that precedes the event. Arnold Barmettler (CalSKY) uses the same MCC ephemeris as I do, except when the event is due to occur in less than about 24 hours, in which case he uses the latest OIG TLE. I have some evidence that typically, the MCC TLE (derived from the results of a numerical integration) gives better positional accuracy (unless the prediction is more than 3 days old, or so), though the OIG update may give better timing accuracy for predictions that are more than a day or two old (which is a bit curious, since you'd think there'd be a direct correlation between timing & position). In any case, one can use Arnold's CalSKY website (and perhaps Chris Peat's Heavens-Above) to complement the email alerts that I send out: http://iss-transit.sourceforge.net/UsingYourTransitReport.html#CalSKY For anyone who's able to record such a transit, it's vital for later analysis to document the precise location (latitude & longitude, to 4 decimal places if possible) and time of the event, and the MCC & OIG TLEs that would apply. (CalSKY has a TLE link which will give the TLE used in its computation.) Tom ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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