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    Re: Polaris plus one
    From: Frank Reed
    Date: 2023 Jun 28, 16:30 -0700

    Kurt H, you wrote in your first post on this topic:
    "I got 34.97 degrees north, 67.24 degrees west."

    That latitude looks good, but I'm puzzled by that longitude. I suggest you give that another go. Be sure to use the latitude from Polaris in the ABC calculation when you get your longitude. That's the beauty (well, maybe not "beauty" but you know what I mean!) in one of these "Polaris plus One" scenarios -- since we know our latitude accurately from the Polaris sight, we can immediately use that to get a longitude from the (averaged) Venus sights.

    You also wrote:
    "I did not do lop because i figured the passage of time was the only important factor in interpolating my longitude between the two longitude points."

    Right. No need for an LOP because our latitude has already been determined by the quick Polaris computation.

    You added:
    "I got lazy and used the Star acorrection table for my Venus site corrections rather than do the individual dip and refraction corrections - is that table accurate for planets too?"
    and in a follow-up:
    "Having looked at correction tables in the nautical almanac, it says star corrections should be used for planets and stars."

    Right. Nothing wrong with using the combined star correction table. Like it says in the description, it just combines dip and refraction. You can check this yourself: calculate any value in the table from the separate equations for dip and refraction. They match, right? You also noticed that the Nautical Almanac has a table to be used for both "stars and planets" for altitude correction (after applying a separate dip correction). That table does not clearly explain that it's really just a list of pure refraction values. But once again, you can test that yourself by calculation. Pick any four or five altitudes at random. Calculate the refraction directly for each. Then compare with the table. They should match right down to the tenth --that is, your computed refraction should be exactly the same as the listed values differing only occasionally (primarily at low altiudes) by even as much as a tenth of a minute of arc. 

    Thanks for contributing on this scenario!

    Frank Reed

       
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