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Excel 2007 : astronomy formula

  1. #1
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    astronomy formula

    Alright, I have some ridiculously simple formulas which are not giving me the correct answer. They are for calculating "Motion in Space" of a star over long periods of time. I'll try to type out the formulas I was given here, then post pics of my spreadsheet formulas and answers.
    Here goes...

    x = r cos theta cos alpha
    y = r cos theta sin alpha
    z = r sin theta

    then

    delta x = (x/r) delta r - z delta theta cos alpha - y delta alpha
    delta y = (y/r) delta r - z delta theta sin alpha + x delta alpha
    delta z = (z/r) delta r + r delta theta cos theta

    then

    x' = x + t delta x
    y' = y + t delta y
    z' = z + t delta z

    then

    tan alpha = y' / x'
    tan theta = z' / sqrt ( x'^2 + y'^2 )

    Now, lets see if I can load the pics. First my formulae then the answers I get. My problem is in the section labeled Motion in Space. The answers I should get are at the end of that section in column G. The constants are all above in blue.

    Thanks, Scott

    Edit: I added a better pic of my answers showing row and column designations. AND "t" is mis-labeled above. So I know it is cell "D13" not "D14". So forget that obvious one.
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    Last edited by Scott S.; 06-28-2010 at 09:31 PM.

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    Forum Expert shg's Avatar
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    Re: astronomy formula

    And the problem is ...?

    Please post workbooks, not pictures, unless you want help with pictures.
    Entia non sunt multiplicanda sine necessitate

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    Re: astronomy formula

    Ooops.
    Sorry I didn't consider I could post the workbook.
    The problem is I should get the answers in column "G" and my answers in column "E" are wildly different.
    I highlighted the section in red.

    Thanks, Scott
    Attached Files Attached Files

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    Re: astronomy formula

    Your entry of the formulas is correct based on what you provided above. Unless someone happens along who knows astronomy and can find your problem more exactly, best I'd suggest is 1) verify your values for r, alpha and theta and 2) verify you have the correct formulas.

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    Re: astronomy formula

    Thank you Masteff,

    At the least, I know I am not completely crazy. And that's a valuable asset in todays world.

    Thanks again, Scott

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    Forum Guru (RIP) Marcol's Avatar
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    Re: astronomy formula

    Aye .... and what will tomorrow bring?

    Suggested reading R. Burns "To a Mouse"

    ...... but moosie thou are blessed compared to me, the present only touches thee
    but I forward, though I canna see, I dread and fear.

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    Re: astronomy formula

    SO, I went to Amazon and found the original text, which included a "different" conclusion to the problem than the one I originally had.

    This is the way the original text reads in The Sky Catalogue 2000.0. Unfortunately this is a math problem I don't understand.

    Can anyone make sense of how r' applies to my problem?

    Thanks again, Scott
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    Re: Excel 2007 : astronomy formula

    Check your units for angle, are you inputting degrees or radians.

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