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    Re: Longitude by Lunar Occultation
    From: Frank Reed
    Date: 2020 Jan 4, 10:09 -0800

    Robin,

    Thanks for the update on the spreadsheet! After your presentation in Mystic last summer, I have a much better understanding of how this works mathematically, and I look forward to exploring the spreadsheet.

    Just to clarify, these calculations still have no limb correction, right? That is, you don't include models of the mountains and valleys on the lunar limb? I can't imagine any easy way to do that in a spreadsheet, so I assume that that's the case. Could you estimate how much error in actual timings result from this? The case you displayed with your graphic would actually be a grazing occultation where the occulted star would blink in and out as it is seen through valleys near the Moon's North Pole. So the ambiguity in longitude for practical observations of occultations is much greater than you're suggesting here, right?

    It's been less than three years (on March 4, 2017) since a few of us observed a grazing occultation of Aldebaran one bitter cold night from a movie theater parking lot just a few miles from here. It's incredible to me that this was only three years ago. It feels like six... And a bitter cold night with the stars out... that's such a contrast to to the rainy tropical "winter" weather we have had in the past few weeks. It's warm and overccast and rainy again today on Narragansett Bay.

    Here are two NavList posts from March 2017 that get into the "flashing" of Aldebaran during this grazing occultation (impressive video linked in the second post):
    my first post describing our observing situation,
    follow-up post with link to video of the event.

    If we analyze that video using your spreadsheet, what sort of results does it give? Are there "practical" recommendations for managing a case like this?

    Thanks for the update!

    Frank Reed

       
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