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    Re: Precomputed lunar distances
    From: Frank Reed
    Date: 2005 Apr 19, 19:44 EDT
    Bill you wrote:
    "In fact that is not what raised a red flag for me.  I had drilled down too
    far and done a scatter graph with Excel, so every or hundredth or thousandth
    was magnified."
     
    Yeah, I wondered if that was part of the problem. Remember, if your input data is accurate to the nearest tenth of a minute of arc, generally you should quote your output data to the nearest tenth as well. Anything beyond that is just random garbage.
     
    And:
    "Now that you mention it, I recall a discussion about bodies
    of equal observed altitude and the 0.6' minute figure."
     
    Only around 37 degrees separation. Try out those equations from my last post. When the altitudes are exactly the same, the refraction correction to the distance in minutes of arc is
    1.9*(1-cos(D))/sin(D).
    You wrote:
    "I apologize to the you and the list for rehashing a subject that was
    apparently covered in October."
     
    You take that back! :-)  There is absolutely nothing wrong with discussing the same topic after a few months off.
     
    And:
    "Regarding my question, "Another hypothetical scenario.  If I take the same
    two stars, calculate true separation of 34d 27.7', they have identical Hc's
    of 1d 36.8', and  hypothetical refraction is -88d, what separation might I
    expect to measure with a sextant?"
     
    I didn't respond to this before because I cannot for the life of me figure out what you're getting at. If you have two stars with an unrefracted distance of 34 deg 27.7' and you observe them down at 1.5 degrees altitude, then the measured distance will be very close to 34d 27.7'. What's this "-88d" number?

    -FER
    http://www.HistoricalAtlas.com/lunars
       
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