XPost: alt.comp.os.windows-xp, alt.windows7.general   
   From: G6JPG@255soft.uk   
      
   On 2026/1/15 20:0:31, R.Wieser wrote:   
   > J.P. ,   
      
   [John by the way :-) ]   
   >   
   > First off, FYI, Paul has minimized his posting about the subject to the   
   > Win10 group only.  If you're not there already it might be a good idea to   
   > take a peek.   
      
   I replied to the posting I did, thinking I was the only respondent -   
   probably in the W7 'group; I saw the other responses when I moved to one   
   of the other 'groups, but too late then to amend my post.   
   >   
   >> If it _is_ light-source-at-centre, then the Y co-ordinate would just be   
   >> the tangent of the latitude   
   >   
   > Somewhere along the road I had a similar thought.   But why than do all the   
   > formules I now have (four at the moment) all do a tan() and than wrap that   
   > up in a log() ?    There must be something to it.   
      
   []   
      
   Indeed! But I can't think what.   
      
   Did you _try_ using just the tangent on a couple of places? Or perhaps   
   just a couple of latitudes, to see if the lines come out where they are   
   on the plot? You'd probably have to do that in the first place anyway,   
   to see what the vertical scale _is_; if doing that for say the ten and   
   forty degree lines (assuming that's what the ones on the plot are) gives   
   different scales, then you'd know it isn't just that.   
      
      
   --   
   J. P. Gilliver   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)