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    Venus ex-mer backsight dipshort
    From: Jeremy C
    Date: 2011 Jan 16, 01:41 EST
    You HAD to ask for that Greg.  Well, since you did, and I happen to be in the proper place to do something completely off the wall like that, I did.  I will say that  I didn't like the results.  I can think of three main sources of error:
       1) i didn't get the apex of the arc when swinging the sextant for azimuth.  There were some clouds so I am not 100% sure with this.
        2) Dip short is incorrect.  The shoreline at that bearing slopes away from me steeply so the range changes quite a bit with azimuth.  I might have the range wrong and at 106 ft and 1.x miles, it's a big correction.
        3) Math blunder.  It's been ages since I've done a back sight, so i might have loused up the math somewhere along the lines.
    For those who are daring enough to try this sight, I'd like to see the following to see if I did something wrong.
    1) "A" for the ex meridian
    2) The correction to Ho for the ex-meridian
    2) Dip short correction
    3) Latitude
    I'm actually really curious to see your math from Hs to final Ho to see if I did this right at all if people are willing to type it all out.
    So here it is, an Ex-meridian backsight, dip short of Venus during the day:
    Date: 16 January 2011
    ZD -6
    Lat 7 deg 16.3' South
    Long 72 deg 26.8 East
    Height of eye 106 feet
    Range to shore 1.25 n miles
    Index error 0.8' on the arc (normally an IC of -0.8)
    Hs observed 102 deg - 20.5' to the shoreline
    Time 10h 08m 52s Local time.
    My Lat was 7deg 8.3' South which is obviously a big error (8 minutes).
    In a message dated 1/14/2011 7:44:39 P.M. Central Asia Standard Time, gregrudzinski@yahoo.com writes:


    Excellent assortment of CN on your last trip. On my short list of unusual observations to try is a daytime Venus ex-meridian/transit back-sight with a dip short horizon. Maybe you can try some back-sight exotica on your next trip and post the reductions. It looks like extra care is needed for this type of sight.

    Greg Rudzinski
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