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    The Spirule for navigation
    From: David C
    Date: 2019 Nov 30, 16:21 -0800

    On another forum we were bragging about the slide rules we had used at school. I pointed out that I was educated in an analogue, imperial (i.e pre-metric) and pre-gps era. I could not resist posting a photo of some of my analogue devices. At the bottom of the photo is a device called a spirule. I purchased it because no self-respecting electrical engineering student was without one  but I never learned how to use it. At the time I believed that it was used to determing the poles of control system equations.

    The device has log tan and log sec scales. Written on it is "Copyright1951 North American Aviation Inc." Therefore I wonder if the spirule could be used for CN?

    All I know about it is that it was made by the Spirule Company 9728 El Venado Whittier, California 90603 USA.

    P.S. In the first photo I forgot to include an image of the vernier scales on my sextant.

    P.P.S .I can post the full instruction booklet if anyone is interested.

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