Luc Desamore May 20, 2012
----- Original Message -----
From: "Bill J Gray" <pluto@...>
> RA/DEC GRIDS IN CYLINDRICAL PROJECTIONS:
> Luc, you're right; to give a concrete example, suppose you've
> set up RA/dec grids for the epoch J-2700. In this epoch, the RA/dec
> grids will converge on Thuban (Alpha Draconis), the pole star of
> 4700 years ago. But Polaris will still be at the top of the map
> (assuming you've set "north up" in the Inversion menu), and if
> you go to a cylindrical projection, it will be the areas around
> Polaris (and Sigma Octans) that are stretched into lines, much
> as the north and south poles are on maps of the earth.
> Guide's concept of where the "poles" are should be epoch dependent.
> That is, if you set the default epoch to be J-2700, then Thuban
> should be at the top of charts, and it should be that in cylindrical
> projections, the area around Thuban is stretched out. I've revised
> Guide to do this. It has the effect for which I think you were
> if Guide's default epoch and the grid epoch are the same, then (in
> cylindrical projections) the grid becomes a simple rectangular grid.
> I'm not posting this quite yet, because I'll be adding display of
> UCAC-4 data (I have a preliminary copy on DVD, and it appears no
> format change will be made for "final" UCAC-4). But this fix will
> appear the next time I post an update.
> -- Bill