An ISS encounter with Venus and Saturn

From: Tom Wagner (sciteach@mchsi.com)
Date: Sun Aug 22 2004 - 18:39:36 EDT

  • Next message: Tom Wagner: "Re: An ISS encounter with Venus and Saturn"

    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
    +   +   +
    
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