WIP : Tessellation rotation

[jgducoin]

I started to implement the rotation tools for the rotation to get ride of the poles issues.

I added a function to rotate a given tessellation, I did not chose to change the functions that create the tessellation itself because there is two of them (tesselation_packing and tesselation_spiral) and if you do another one in the futur the tool to rotate will still work in this way.

I putted by default a rotation of +90deg in Dec but it can be changed in input. I putted by default as name of the new tessellation : [telescope]_rot.tess, but it can be changed in input.

Questions on how to implement it in gwemopt: -Do you want this new tessellation to be created by default for each telescop? (at the same time we create the first one) -How do you chose to take the rotated tessellation and not the usual one? By checking only the position of the 2D max probability of the skymap? By checking the number of tiles in the 90% skymap which are near poles? By checking if there is problematic tiles? Other method ?

If we chose the use that tool that mean we have to add a security which check that the rotated tessellation is available before calling it (as it exist for the usual one).

Here are some plots of the results: -normal tessellation (using packing method):

-rotated tessellation taking previous one as input:

Anyway i need to test the results on a skymap near pole before merging anything, I will let you know.

(Sorry for the long post)

[mcoughlin]

@jgducoin do you have examples of maps that go through the poles for which this is now dealt with properly? I am curious in particular about the healpix indices.