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    Re: Bearing of the sun at a given time from a given position
    From: Frank Reed
    Date: 2015 Nov 18, 14:12 -0800

    Steve Bryant, you wrote:
    "the embarrassments continue"

    Steve, you shouldn't be embarrassed! I've met many people who have studied celestial navigation in the traditional fashion who are stumped by this. The problem is that traditional celestial is generally taught in ritualistic fashion, grotesquely over-burdened with un-necessary details and opaque jargon, leading to the classic inability to see the forest for the trees. The traditional style of teaching the standard "intercept method", as exemplified by "Power Squadron" classes today, is like a bad day at Sunday School --repetition of the catechism, regurgitation of endless un-necessary definitions. It creates excellent robotic navigators, perfectly suited to the navigational tasks of the 1970s.

    What is the intercept method? At its most basic level, the intercept method is comparison against simulation. We observe a celestial object's altitude, and then we compare that altitude with a simulated observation from some nearby location at the same instant of time. The simulated observation calculation gives us both the altitude and the azimuth of the celestial object. All of the standard pen-and-paper "intercept" methods of celestial navigation can simulate the appearance of the sky from any point on the Earth at any instant of time.

    In the modern world, when we have access to computing power, we can get the same simulated sky information much more quickly using any tool from an almost endless variety of software packages and apps. At one end, there's the dependable USNO web app (which Gary pointed to earlier today, and which many of us use on a regular basis). In the USNO web app, you enter date, time, and location, and it spits out the altitudes and azimuths for all bodies above the horizon. It's a text-based simulation of the sky, and we can compare any number of (corrected) altitudes with the values as computed. At the other end of the spectrum of apps, there are complete "desktop planetarium" packages like Stellarium (one among many) that can provide fundamentally the same information in a highly visual form. No matter what approach you use, you can get the bearing of the Sun easily using many basic tools.

    Frank Reed

       
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