[AstroPy] Vizier projection

[Gabriel Perren]

Hi everyone,

I'm trying to reproduce the projection applied by Vizier to obtain the (_x,
_y) columns. According to what is stated here
http://cdsarc.u-strasbg.fr/vizier/vizHelp/xy.htx, these columns are the
*arc projection* of the `(RA, DE)` coordinates.

I'm trying to reproduce these values based on the equations shown in the
above link, but I can't seem to get the proper results. See for
example the attached
image with a queried region of 0.2 deg length around the center `(100, -80)`
.

The plot to the left are the `(RA, DE)` coordinates, the middle plot are
the projected `(_x, _y)` positions by Vizier, and the right plot my
attempts to reproduce these last values (the code is below, test.dat file
here: https://justpaste.it/623lj)

What am I doing wrong? And, can astropy apply this projection?

I've also posted this question to SO here:
https://stackoverflow.com/q/68985179/1391441

Cheers,
Gabriel
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