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    Re: Refraction
    From: Marcel Tschudin
    Date: 2005 Aug 5, 00:33 +0300

    Hello Frank


    You are right, in realty it would only be some approx. hundred lines of programming. May problem however is that I lost during more than 30 years after leaving university the know how on how to do. What 30 years ago would probably have been a little problem became now a “big problem”. That is why I’m looking now for the easy way, i.e. an analytical approximation…


    You wrote:

    “Assuming your goal is to create accurate simulated views of landscapes (is it??), that's probably the best way to proceed.”


    No, the program is just to calculate some astronomical data, but those with a higher accuracy than normally available. I know there have been done very good simulations of landscapes even in very realistic moon shine conditions.


    You wrote:

    “Then you can include as much detail as you want --temperature inversions, pressure gradients, anything-- and you can calculate extinction at the same time.”


    If  I remember right refraction is caused to a large extend by the temperature gradient, i.e. the –6.5°C/1km for the first 11km of the standard atmosphere…and being able to calculate extinction for altitudes below +5° altitude would also be of interest for some other aspects; further more I also would be interested in how to calculate the visible brightness density of the sky (relative to the position of the sun)… Yes, it all could be calculated. But as I mentioned, my know how has in the last 30 years deteriorated…I therefore would need now very good text books with program descriptions and sample calculations.


    But for the moment I really would be very happy just to be able to calculate refraction values for negative altitudes…


    Greetings Marcel
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