Re:Significantly different predictions by different programs

From: Greg Roberts (
Date: Tue Oct 31 2006 - 05:07:49 EST

  • Next message: Björn Gimle: "Re: significantly different predictions by different programs"

    Afternoon all,
    Noted the problems with HEAVENSAT. I did raise the
    manner of  how the authors program worked and here is the
    answer I got:
    From: "HeavenSat" <>
    To: "Greg Roberts" <>
    Subject: Re[2]: New version
    Date: 20 October 2006 05:26 PM
    GR> I have been running the full SpaceTrack catalog (~8500
    GR> objects) + Classified.TLE (~170 sats) with no problems,
    GR> but Im curious as to how the program manages it. At the
    GR> start one selects a time and how wide a window and then
    GR> displays the satellites available , but its not the complete
    GR> 8500 objects) - I guess you only list satellites that are
    GR> not more than (say ) 20 degrees below the horizon?, so
    GR> if one wants to use a time (say) 4 hours later it is
    GR> necessary to redo the complete "calculation" as the
    GR> number of satellites visible, and potentially visible in
    GR> the near future, is different from what it was for the first
    GR> run - clever!
    You are right. Every 7 minutes program calculates all satellites 
    that will be above horizon for about 10 minutes before and 10 
    minutes after date of recalculation.
    It helps to shrink all 8500 satellites to 1000 for calculating in 
    real time. In addition in real time frequency of recalculation 
    for each satellite depends on its angular speed to observer 
    relative to field of view and window viewport size, except 
    for selected satellite.
    GR> Do you subscribe to the SeeSat news group- its the group
    GR> of Visual satellite observers - free of course - and where
    GR> most of the serious trackers post their observations.
    Not, but I periodically read SeeSat archives on site.
    Best regards,
    so maybe Aleks's comments might explain the situation better.
    I did indeed find that one can go significantly past the window 
    defined at the start of the program but eventually I did get a 
    wrong field display so all I did was CLEAR the stuff in 
    memory and defined a new "window" time and all was then 
    correct.  However it is clear that this could be a problem so 
    Ive posted the SeeSat comments to Aleks.
    Mike said he couldnt get a display of the objects RA/Dec
     --true only az/el are shown in real time in bottom left corner, 
    but if you right click on the satellite you will find 
    RA/Dec/phase angle/long/lat etc.
    One may notice that in the latest version (1.97) one can also 
    produce an ephemeris. I must admit the format of the 
    ephemeris is biased in my favour and strangely (:-)))  is 
    how I requested it-- it just happens to be the format needed 
    to drive my CoSaTrak system :-)). No doubt other 
    observers may want RA/Dec output as well - Im sure Aleks
    could add this to the ephemeris with no problem so let 
    him know your wishes.
    With any new program there are bound to be glitches - its 
    only by letting the author of the program know there is 
    that it can be corrected.
    So I still stand by my statement that I regard this as one 
    of the best programs for visual observers - video 
    especially - that has so far appeared . If anyone knows 
    of a better one I certainly would like to know about it !
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