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    Re: Beginner with inaccurate results
    From: Asbjørn Djupdal
    Date: 2005 Aug 31, 09:12 +0200

    Fred Hebard  writes:
    > It's more accurate to determine the index error by first touching the
    > reflected lower limb to the upper limb, recording the result, then
    > reversing and recording that result.  Index error is half the
    > difference.  Usually three measurements on each limb is more accurate
    > than one on each; measure one then the other three times.  As a check
    > on your interpretation of contact, you also can calculate the sun's
    > semidiameter from these measurements; it's one fourth of their sum.  It
    > should be no more than 0.1 arcminutes of that recorded in the Nautical
    > Almanac.
    I'll do this after work today (weather forecast is promising).
    > Always turn the index screw in the same direction when bringing the
    > limbs into contact.  Never back off on the index screw to perfect the
    > contact
    > Only adjust the mirrors if the index error is out by more than 1 or 2
    > arcminutes.  This shouldn't be necessary very often.  You don't want to
    > be constantly adjusting them.
    OK.  This is good to know.  I always adjusted the mirrors, which is
    difficult with shades in place.
    > If you use the clear glass on the horizon, you can leave the same
    > shades in place.
    I guess refraction through the glass on the horizon is never a problem?
    Right now I have difficulty reasoning if this could be problematic or
    Thanks for your help.

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