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    Re: Position from a photo
    From: Paul Dolkas
    Date: 2013 Jan 12, 14:39 -0800

    With all due respect to the ingenuity of the various attempts to solve this using celestial navigation, I still think the easiest and most practical way of doing this is to take a few shots with 2 or more distant landmarks in each. That way you don’t have to worry about the date, time, horizon… or existence of a fortuitous comet!


    ‘Course, I suppose Conan Doyle would have done it your way…


    Paul Dolkas

    From: navlist-bounce@fer3.com [mailto:navlist-bounce@fer3.com] On Behalf Of Brad Morris
    Sent: Monday, January 07, 2013 7:34 PM
    To: NavList@fer3.com
    Cc: NavList@fer3.com
    Subject: [NavList] Re: Position from a photo


    Hi Frank

    I do like the comet idea.  Its really pretty neat!  Using a rare astronomical event.  It doesn't even have to be deliberately encoded.  It can be discovered by Geoffrey's celestial navigation hero, completely by 'accident' and 'hard work'.

    Using modern methods, the trajectory of a comet is well known.  For example,the one expected late this year which is supposed to be bright.  Or any NEO which is tracked for impact, decades in advance

    I wonder if the trajectory could be so well established so as to make the 'discovery' of position on earth by photo accurate and years later in retrospect, a feasible 1940s activity.  I'm not curious about the computational power or the ability to determine the position given the trajectory.  That's just grinding out the solution.  Its the knowledge of the parameters of the trajectory, using the technology of the time, on a comet that I'm curious about.

    Sure, planetary trajectories (orbits) were worked out, but over long term and many observations, hundreds of years ago.  Would that be possible for a swiftly moving one time event like a comet?  In the 1940s? 

    Note: this is a question, not a statement. I don't know the answer.  But I'd like to know!

    Kind Regards
    Brad Morris

    On Jan 7, 2013 4:15 PM, "Frank Reed" <FrankReed{at}historicalatlas.com> wrote:

    Ok, since this is for fiction, you might consider adding a fictional astronomical event. As long as it's consistent with similar astronomical events, that wouldn't be too much of a deus ex machina solution, or would it?

    Do you remember Comet Hayakutake in 1996? It was just spectacular under a dark sky. I was living in Chicago, and I borrowed a friend's car to go out to dark skies west of the city. While on the highway and getting further from city lights, I opened the car's roof hatch and it was the most beautiful comet I had ever seen, the tail stretching some 40 degrees across the sky near the North Star. I nearly drove off the road. The center was as bright as Arcturus and it was moving across the celestial sphere at approximately 1' per minute of time, double the Moon's rate. Photographs of its position taken in 1996, can be used to determine GMT to within ten seconds or better. Now that comet passed about 10 million miles from Earth. If you invent a fictional comet and let it pass at 2 million miles, with the same speed relative to the Earth, its apparent angular speed would be five times higher, and you could get GMT within two seconds. Such a comet would only be visible for a few nights, but that would make it all the more exciting. Maybe it could be "Comet Wassermann, known in Britain as 'Hitler's Damn Comet', some feared it would destroy the Earth in the middle of this terrible war... etc., etc." :) In a photo taken in twilight, it would appear as a slightly fuzzy bright star with just a hint of a tail. Perhaps its cometary nature would only be apparent when examined carefully with a magnifying glass... or something like that. You would still need some Sun altitudes for latitude and local time. I think it was Bill B. who suggested using Ken Gebhart's method here of estimating the Sun's altitude by the flattening of the image as it's rising or setting. That might work. Or maybe a photo of a low altitude Sun reflected in a still bowl of water...


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