My First Positional Measurements!

From: Cees Bassa (c.g.bassa@phys.uu.nl)
Date: Tue Aug 22 2000 - 15:59:32 PDT

  • Next message: Leo Barhorst: "Superbird obs Aug 23"

    Hoi,
    
    After reading the latest, very interesting, threads on measuring a 
    satellites position, I dared to give it a try.
    
    For this night USA 129 and USA 144 both made an interesting pass. I found 
    one suitable star in Bootes which USA 129 would fly along closely and for 
    USA 144 I found a star in Cygnus and one in Perseus.
    
    Before each measurement I located the star in my 1000 mm F/10 refractor 
    with a 40x
    eyepiece. Using the predictions with Skymap 6.4 I set my watch so it 
    started beeping the first whole minute closest to the time the satellite 
    would pass my star and I started counting with it so
    I had a guess when the satellite would be expected. So here I am, looking 
    through the telescope with my thumb on the startbutton of my stopwatch. 
    Here comes the satellite and I push it when it gets closest to the star. 
    Then I take a look at it's motion relative to the stars in the field so I can
    guestimate it's RA and Decl.
    
    Next to do is to find the time. I used my watch, which I had synchronized 
    with the time given on the something like CNNtex on TV (please forgive me 
    when this is a stupid way to find an accurate time but it is the best I 
    have at the moment). I used the watch to substract the time the stopwatch 
    gave me to find the time of the observation.
    
    Finding an accurate position is a bit more difficult. I have no idea 
    whether the right ascension and declination of the epoch of the date or the 
    J2000.0 equatorial coordinates. Someone enlighten me here please. I used 
    Wil Tirions Sky Atlas 2000 to locate the stars on the sky and checked the 
    positions of the stars with Skymap Pro 6.
    
    So here are my observations:
    Sat/NORAD/COSPAR		Date (UT)	Time (UT)	R.A.		Decl.
    USA 129/#24680/96072A	2000-08-22	21:38:55.92	14h52m24.3s	2024'14"
    USA 144/#25744/99028A	2000-08-22	21:53:30.12	20h30m07.6s	4857'18"
    USA 144/#25744/99028A	2000-08-22	22:01:30.83	02h18m05.5s	5754'18"
    
    The equatorial coordinates given here are those of the equinox of the date. 
    But I can provide the J2000 coordinates if necessary.
    
    The coordinates of my observation place are:
    Beesd, Netherlands
    Latitude:	5154'41" North
    Longitude:	0525'10" East
    Elevation:	-2 meters
    
    I'm sorry not to provide you with the data in the correct formats, but 
    since this is the first time I do this I am not sure what all those numbers 
    represent in the more professional observations sent to this list. I can 
    fish out the sat, the date, time and RA/Decl, but that's about it. If some 
    of you guys can tell me what each column in Russel Ebersts and Ted Molczans 
    observational reports represent I would be very helpfull.
    
    Looking forward to replies that explain the questions I've asked in this 
    mail and looking more forward to do some more observations.
    
    Regards,
    	Cees Bassa
    
    
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