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    Re: Moon photo
    From: Frank Reed
    Date: 2012 Aug 4, 11:53 -0700

    Right, Tom. I just thought of that seeming "non sequitur" a few minutes ago and came online to post about it. This photo is part of a gallery of images. If you follow the link Bob posted previously, there is a shot that shows "HMS Belfast" in the foreground, which also confirms the general location, and in that photo, you can see a walkway to a pier which is tilted at a high downward angle. Hence low tide.

    Checking the tide table here, http://www.pla.co.uk/pdfs/hydro/LondonBridgeTower_2012_Q3.pdf,
    which happens to be for almost this exact location, sure enough, low tide was at 21:38 GMT, only an hour and a half after my estimate of the time that the photos were taken.

    Just to emphasize, the location can be determined almost exactly without reference to the second photo. 1) The date (assuming it's within the past few days) is determined by the Moon's phase: August 3. 2) The distance from Tower Bridge is determined relatively well by the angular size of the Moon compared against features of known size on the bridge (e.g. the Olympic rings): 2800 feet. 3) Assuming the photographer is at approximate street level in London, the alignment of the Moon with the known physical height of the bridge structures then determines the Moon's altitude in degrees fairly well: alt=1d 10'. 4) The Moon's altitude on this date (and at a known distance west of Tower Bridge) then gives us the local time and also the Moon's azimuth: 21:05:10 or 20:05:10 GMT +/-15 seconds (revised from my previous estimate), Azm=101.7deg. 5) Draw a line on that reversed azimuth from the center of Tower Bridge out to the right distance, and you find you're right on the east side of London Bridge near the south shore of the Thames --a perfect spot to shoot this sequence of photos. And if you go there in Google Street View and pan around towards Tower Bridge, the perspective of HMS Belfast with the bridge in the distance behind does in fact match the second photo. Note also that the photographer has moved between the first and second photo since the Moon is aligned with the center line of the Olympic rings in both photos while the Moon would have been rising at an angle of about 51.5 degrees (London's latitude) relative to the vertical. From the angular shift, the photographer must have walked about thirty feet (+/-3 feet!) north between the two photos. The second photo was taken about 3.4 minutes after the first.


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