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Focal Points Made Easy

by Brad
(Las Vegas)


I recently posted about finding focal points, and the mathematical method seemed a bit confusing. I decided to explain it all in one simple picture, step-by-step.

I think that once you walk through this one time, it will make complete sense. Good luck.



  • For those of you who really get into the mathematical realm of solar cooking you can download an excel spread sheet for calculating parabolic solar cooker focal points and energy out put; and there is a page in the same spreadsheet for Solar Oven Energy Output Calculations as well...the graph is in a zip file that you download to your computer
    Solar Parabolic Focal Points Graph file




    • Comments for Focal Points Made Easy

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    Jul 25, 2018
    Rating
    starstarstarstarstar     		focal point length if diameter is 1.2m NEW
    by: Anonymous

    focal point length if diameter is 1.2m
    Dec 18, 2010
    Rating
    starstarstarstarstar     		Easier Picture
    by: Anonymous

    Uploaded the picture to Nathan, for posting in a way that is more readable or download-able (i.e. Right Click, Save As in Explorer), than the current page format.
    Dec 18, 2010
    Rating
    starstarstarstarstar     		Great Link
    by: Brad

    Note: I misstated on the picture that the formula was derived from "y=x2/4y" when it should be "y=x2/4f".

    That program link is excellent. Thanks for sharing that one.
    Dec 18, 2010
    Rating
    starstarstarstarstar     		Focal Points Made (Too) Easy :)
    by: Luther Krueger-Minneapolis

    I'm a firm believer in knowing how to do the math for things and your calculator posting helps explain focal points well.

    For those who want to toy around with parameters on the fly, there's a program you can download and run the numbers based on how many segments you'd need for your reflector, how wide the diameter, and how deep the "bowl"--

    http://mscir.tripod.com/parabola/

    It will automatically show where your focal point will be. It doesn't matter whether you use meters or feet, so long as the dimension units are the same.

    LK

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