Early this morning I observed and videotaped a rare close encounter of the ISS with Venus then Saturn about 33 seconds later. Thank you Tom Fly for your alert service! I –tried- to compare about 8 hours before, a TLE from H-A and one from CelesTrak. I –thought- I chose the best place to be for ONE of the TLEs in two locations a few miles apart. I made a “one-legged route” in my GPSr (GPS receiver). The problem I encountered was this: when working with the two satellite symbols in my “TheSky” software, I worked with the CelesTrak ISS image when determining a best place to be for the northernmost point then I mistakenly worked with the H-A ISS image when determining the southernmost point!!!! [I cannot figure out how to automatically label the sats on the screen.] Good thing is, I just made a corrected route in my GPS to see how far off I was and could not tell that the point where I was when I observed the event was more than maybe 5 feet away from where I wanted to be for the CelesTrak track. Fortunately I chose to be nearest the northernmost end of the route which helped. When the ISS crossed my FOV (100X) I was watching Venus. I estimated that it missed Venus by about 5 of its diameters on the sunlit side of the planet. In my, TheSky program that looks like it must be around 0.034 degrees. It then went on to miss Saturn by about 0.174 degrees. A nice show! The video camera I used is a digital 8mm Sony with a “color-slow-shutter” feature that I chose to use. The camera was on a tripod. It gets me down to a magnitude of +6. That setting I knew would bleach out Saturn, let alone Venus, but it did make the Station highly visible. I zoomed in so that Saturn was in one corner and Venus was in the opposite corner. H-A predicted the ISS magnitude to be 0.1 The color-slow-shutter feature takes ¼ second exposures so the satellite appears to move jerkily along. It is still a neat video though! As the time approached, a car drove by facing its headlights toward my camera. I would never have guessed that on a remote country road before 5 AM on a Sunday that 5 cars would drive by in the half-hour I was there! I found that I didn’t have enough time to set up my digital still camera properly (always give yourself a half hour more time than you think you will need!!). When the ISS was about 5 seconds in time from Venus I discovered that Venus had drifted out of the FOV of my scope! Fortunately a slight twist on the RA control brought it back in again. The details of the event follow. Both TLEs were obtained about 02:00, UTC 8/22/04. ISS TLE H-A 1 25544U 98067A 04234.90734979 .00023664 00000-0 19390-3 0 5005 2 25544 51.6341 350.2222 0008007 119.3321 341.8024 15.70344899328648 ISS TLE CelesTrak 1 25544U 98067A 04234.52520006 .00019176 00000-0 15831-3 0 4971 2 25544 51.6337 352.1743 0007791 117.8838 341.4189 15.70319860328588 The closest approach to Venus was approximately 09:49:20 UTC, 8/22/04. [It was 4:49:22 AM CDT on 8/22 in the Midwest USA. I hope I got the UTC time right.] My GPSr read position was 42 degrees 36.864 minutes (42.6144 d) by 92 d 23.179 m (-92.3863 d). The altitude was 926 feet according to topozone.com. See http://www.topozone.com/map.asp?lat=42.6144&lon=-92.3863&datum=nad83&u=5). I used http://www.cosports.com/tools/gps_coords.htm to convert the coordinate units back and forth. If anybody needs clarification about any of the numbers I’ve included or inadvertently left out, feel free to ask. Clear skies! [Mine was this morning.] Tom Iowa USA + + + ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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