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    Re: Timesight at sunset?
    From: Greg Rudzinski
    Date: 2013 Jan 10, 08:57 -0800

    Doug,

    Good job spotting the green flash. Now look for the blue flash ;-)

    The online calculator has your sunset observation within 6 NM. Not bad. Your watch could be slow some seconds though. Give it a time check double check.


    Using the formula: Arc Cos[ (SinHo + SindSinL) / (CosdCosL) = LHA(t)

    Ho = 359* 8' (- 52')
    Dec = 21* 56.1' S
    Lat = 20* 1.4' N

    GHA = 238* 16.6'
    LHA(t) = 82* 34.1' (TS Formula)
    Long = 155* 42.5' W


    Greg Rudzinski

    P.S. Sunset LOPs are generally reserved for emergency navigation use because of unpredictable refraction at the horizon.


    [NavList] Timesight at sunset?
    From: Doug MacPherson
    Date: 9 Jan 2013 21:11
    All:

    Sitting on a beach on the west side of the big Island of Hawaii, sans sextant, what is a frustrated navigator to do?

    With a perfect sunset every night, can it be exploited for an accurate longitude with a time sight?

    Alas, Equipped only with my iPhone, and my eyesight, I think I will need some help if any are willing. I don't have my copy of Norries or an almanac.

    On January 9, 2013 the upper limb of the sun dropped below the horizon at 18:00:35 Honolulu time (on my i-phone) with a noticeable green flash :)) I was standing on the beach at the water's edge. I am 6 feet tall. My latitude is 20.023 degrees north. I cannot determine index correction, my eye doctor is back in California :)

    78 degrees Farenheight. 29.89 inches of mercury.

    Can anyone help me with determining what my longitude is? The sun's azimuth at that time?

    Also were sunsets and sunrises ever used for practical purposes for navigation besides determining azimuth for compass error?

    Doug
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