Lunar transits w/SkyMap

From: Matson, Robert (ROBERT.D.MATSON@saic.com)
Date: Wed Jan 24 2001 - 12:46:04 PST

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    Hi Kevin and list,
    
    > I use rob's skymap program to find lunar transits, then have to go through
    
    > each one to find one that is sunlit. That's because right now skymap, 
    > doesn't use the lighting menu to compute transits.
    
    You've mentioned this to me before in private e-mails, but
    I figured you would soon discover you were mistaken.  SkyMap
    *does* pay attention to the satellite lighting constraint for
    lunar transits.  You can prove this to yourself:  go into the
    lighting constraints menu and set F1 and F2 to No constraint,
    and F3 to Night Only.  Do a 2-hour search from say 6pm to
    8pm for January 27th.  (Set the transit tolerance high enough
    that you get at least 5 or more tracks).  Then go back into the
    Lighting Constraints menu and change F1 (the satellite lighting
    constraint) to Sunlit only.  Then rerun your plot.  Many (and
    perhaps all) of your tracks will disappear, because most will
    not be sunlit.
    
    I do agree that SkyMap does not pay attention to the ground
    site lighting constraints when doing transit searches.  I
    figured no one would intentionally do a lunar transit search
    during a time window that spanned daylight, so it was
    an unnecessary waste of CPU time to compute the lighting
    condition at the ground site.  Perhaps with today's fast
    computers, people don't care if it runs a few seconds slower,
    and I can put the check in there.
    
    I realize that SKY64.NEW (or SKY65.NEW if you're a beta tester)
    says under the mods from 5.0 to 5.1 that SkyMap doesn't use
    the lighting constraints when doing transit searches.  At
    that time, it didn't.  In version 6.3, the functionality was
    changed so that the satellite lighting constraint IS used
    for lunar transits.  While this fact isn't explicitly stated
    in the update notes for mods from 6.2 to 6.3, it is implied
    by the remarks about satellite visual magnitude and blue
    tracks for satellites that aren't sunlit.
    
    To avoid future confusion, I've modified the update notes in
    the 5.0 to 5.1 section to say that the *ground* lighting
    constraints are ignored rather than all lighting constraints.
    
    Best wishes,
    Rob
    
    
    
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