Re: TLE based on Az-El data

From: Tony Beresford (
Date: Mon Aug 09 2004 - 22:30:15 EDT

  • Next message: Daniel Deak: "Re: TLE based on Az-El data"

    At 10:52 10/08/04, Daniel Deak wrote:
    >Hi all,
    >To save time while taking positional data on a satellite, I intend to build a tracking system for my binoculars that could read azimuth and elevation data at the same time as time data either at pre-determined time interval or at the click of a button or trigger.
    >I have a question though. Is there a program that use this kind of data directly to calculate an orbit and generate TLE. To know if my efforts will be worth the time and money, I'm asking if analysts prefer to use AD-dec data instead of Az-El or if any format is OK for all analysts.
    I doubt whether any of the current programs have been set up to do that Daniel. You just have to convert the time + Altaz
    to RA-Dec . The resulting RA-Dec is apparrant rather than mean, and then precess it to epoch J2000.0 or B1950
    to be consistent with other measurements. Most of my moonwatch observations from 1966 on word were alt-Az.
    The practical problem is getting alt-az measurement to a similar accuracy to that possible with Ra-Dec.
    The mount I used had a set of custom made circles, painstakily copied by a friend from a theodilite circle.
    To get accurate results you have to calibrate the mount using star sightings to correct for
    imperfect mount geometry and levelling errors. Relatively easy to get 1 degree accuracy, require hard work
    and  time to get 1 arc minute. My best average moonwatch residual was 100 arc seconds. Gordon Taylor was
    averaging 50 arc seconds with a 5 inch reflector and star measurements. I was using a 20by 125 monocular
    known as the Moonwatch apogee telescope.
    Tony Beresford
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