Re: Close Calls

From: Brad (
Date: Mon Aug 06 2001 - 12:45:31 PDT

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    I've been observing sats with an LX200, using CSat and LXSat software,
    for about 2-1/2 years.  Two years ago, after observing a few "close
    calls" in the scope, I wrote a PERL script that predicts them.  There
    are actually many of them each night, the number depending on the
    angular separation selected.  Since my setup yields a 1.4 deg fov, I
    usually set the script for 1.0 deg.  As a result, I have seen many of
    these.   I've usually watched them through the scope, but sometimes use
    the 7x50 finder, so some would be visible in binoculars or naked-eye. 
    Of course, it works better at a dark sky site where fainter sats can be
    seen.  I haven't done this much lately, but I ran the program for
    tonight at my location and got 55 close calls for sats with Std Mag <=
    6.0 during a 2-hour period.  The two that will be physically closest are
    at about 36 km. from each other.  Since the Alt shows only a 2 km
    difference, they may get much closer than 36 km, but not when they're
    within 1.0 deg from my location.  Here's the listing for it (the tabs
    may get screwed up in the email):
    Sat Name        Mag     Time        	El    	Az      Range  Alt    Sep
    Cosmos 1833     5.6	21:32:23	22.1	056.5   1767   0852
    Meteor 2-9 r    5.5	21:32:23	23.0	056.2   1731   0854   0.95
    BTW, the script doesn't do the pass calculations, it scans a Traksat
    batch tabular output file.  So it requires having both Traksat and PERL
    on the system.  If you want to try it, I'll email it to you.
    Los Alamitos, CA
    >      Last night I observed 25018 (Lacrosse 3 rkt) passing overhead.  As the
    >      sat passed into Andromeda going East I noticed another sat (which I
    >      have not been able to identify) going South to North, about the same
    >      mag as 25018.  Anyway the 2 sats passed very close from my point of
    >      view (too quick to gauge just how close, but very close indeed!).  Of
    >      course I'm sure the satellites were really some distance apart but
    >      having seen a couple of these 'chance close encounters' recently I
    >      just wondered if anyone else had seen some really close passes of
    >      un-related satellites?  Its a fascinating thing to see.
    >      If anyone has any idea about my UNID that 'buzzed' 25018, I'd be
    >      grateful.  It was going South to North, just about reached maximum
    >      elevation of around 20 degrees in the East at 21:22UT as 25018 passed
    >      it.
    >      Regards
    >      Matt Fawcett
    >      53.893N 0.273W 50m
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