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    DIY planisphere: how to begin with it?
    From: Tony Oz
    Date: 2016 Oct 17, 02:58 -0700

    Dear List,

    I'm trying to build a planisphere for my lattitude (60°N) using Toshimi-san's as an example. Unfortunately his project does not have covers for lattitudes higher than 50°.

    Creating the double-sided map disk was easy: I plotted the list of navigational stars in polar coordinate system linearly along the polar distance radiuses in the range of 0° to 115° (as on Tashimi-san's example).

    Where I stuck is the calculation of the cover for 60°N.

    As I can understand the task - I must obtain the coordinates of the poins on the sphere for which the zenith distance to the point [Dec 60°;SHA 0°] equals to 90°. I.e. I must plot the whole LOP of Ho=0° around it. I think I must somehow solve the triangle for the azimuth (Az) variable changing in the 0°~360° range to get the Lat;Lon for all the points on that LOP. Then I must transfer those points on a planispere and cut-out the edge to obtain the covers - one for northernly view, another for southly view.

    Could you please give me a hint which set of formulas is the best for me?

    There is another planisphere project with not so convenient maps - but it features the very usefull height and azimuth grid. I'd like to learn how to create such a grid for an arditrary lattitude too.

    Thank you in advance.

    Regards,

    Tony

       
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