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    Re: In Flight CN Using 10" Slide Rule
    From: Greg Rudzinski
    Date: 2011 Dec 24, 13:27 -0800

    See the linked image to find an example of sight reduction using a pair of K & E 4080-3s. The K & Es are each showing the cosine product for their respective star. Hc look-up is done with a pocket trig table and azimuth done by Rust diagram or 2102-D.

    Greg Rudzinski.

    [NavList] In Flight CN Using 10" Slide Rule
    From: gregrudzinski---com
    Date: 22 Dec 2011 13:15

    It should be possible to effectively reduce sights using a 10" slide rule quickly enough to be practical when traveling at jet speeds. I found the Bygrave formula hard to work with in low light conditions and when meridian angles and declinations were greater than 45 degrees. This sent me back to the standard sin cos formula to see if slide rule precision could be tightened up some for good enough results. What I have settled on is an index card with pre-calculations (by trig table) so that the only slide rule action needed in flight is to pre-set the slide rule index and move the curser to the cosine of the meridian angle. Final arc sin look-up is done using a pocket trig table. Azimuth from a 2102-D is good enough using the Aries LHA for the observation and the closest latitude template. Stars have fixed declinations so the pre-calculated index card can be used repeatedly requiring only a curser move to the new meridian angle cosine. Trials have been very fast and mistake free. Precision is within 4' moa for altitudes below 45 degrees.

    The linked example shows a Sun (bubble octant) reduction for UT 18:53:00 12/22/2011 that is within 3.4' moa of the correct reduction.

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