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    Angular Distance Between Stars By Camera and Sextant
    From: Greg Rudzinski
    Date: 2012 Sep 15, 21:37 -0700

    This evenings star pair observations included Vega Deneb (by sextant) and Alioth Alkaid (by sextant and camera). This time the on-line William's GC calculator was used properly to calculate true star pair distance. The Vega Deneb pair was corrected for refraction using the approximation method of 0.1' per 5* of angular distance. The Alioth Alkaid pair was corrected for refraction using the table provided by Mike Burkes (attached).

    Vega Deneb Hc 85*65*
    23* 50.1' observed distance by sextant
    +0.5' refraction correction (approximation 0.1' per 5*)
    23* 50.6' true distance
    23* 50.8' true calculated distance by William's on-line calculator
    Low 0.2'

    Alioth Alkaid Hc 31*37*
    10* 27.1' observed distance by sextant
    +0.3' refraction correction by table
    10* 27.4' true distance
    10* 27.6' true calculated distance by William's on-line calculator
    Low 0.2'

    Alioth Alkaid
    10* 28.0' observed distance by camera
    +0.3' refraction correction by table
    10* 28.3' true distance
    10* 27.6' true calculated distance by William's on-line calculator
    Hi 0.7'

    The camera image was disappointing showing 4' wide stars. Settings were ISO 1600, f 2, 1/8 sec, infinite focus using a fixed prime 50 mm lens. Sextant results were good.

    Greg Rudzinski


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