Create a MOC from an astropy Table

import matplotlib.pyplot as plt
from astropy import units as u
from astropy.visualization.wcsaxes.frame import EllipticalFrame
from astropy.wcs import WCS
from astroquery.vizier import Vizier
from mocpy import MOC

Let’s load a VizieR catalog

viz = Vizier(columns=["*", "_RAJ2000", "_DEJ2000"])
viz.ROW_LIMIT = -1  # sets the limit to infinity
table = viz.get_catalogs("I/293/npm2cros")[0]

print(table)

 _RAJ2000   _DEJ2000    NPM2   KLA  RAJ2000   ...  IQ  IN r_Star  mag  tyc
   deg        deg                             ...                 mag
---------- ---------- -------- --- ---------- ... --- --- ------ ----- ---
339.638333  83.166667 +83.0016 HPM 22 38 33.2 ...   0   0    811 14.20
339.638333  83.166667 +83.0016 HPM 22 38 33.2 ...   0   0    813 14.20
349.530833  83.010556 +83.0022 VAR 23 18 07.4 ...   0   0    843    --   T
349.530833  83.010556 +83.0022 SRA 23 18 07.4 ...   0   0      1  9.60   T
323.854167  82.997222 +82.0030 UBV 21 35 25.0 ...   0   0      5 10.08   T
332.107917  82.747500 +82.0055  WD 22 08 25.9 ...   0   0   1012 16.00
332.933750  82.607778 +82.0059 HPM 22 11 44.1 ...   0   0    811 16.70
335.088750  82.970833 +82.0065 HPM 22 20 21.3 ...   0   0    811 11.00   T
337.119167  82.763889 +82.0074 UBV 22 28 28.6 ...   0   0      5 10.42   T
337.274583  82.662222 +82.0075 HPM 22 29 05.9 ...   1   0    811 17.40
       ...        ...      ... ...        ... ... ... ...    ...   ... ...
257.227500 -23.094167 -23.0151 ELS 17 08 54.6 ...   0   0    511 13.50
267.989583 -23.012222 -23.0162 CMC 17 51 57.5 ...   0   0    817 11.13   T
267.989583 -23.012222 -23.0162 ELS 17 51 57.5 ...   0   0    252    --   T
270.244583 -23.032222 -23.0164 CMC 18 00 58.7 ...   0   0    817 10.52   T
270.244583 -23.032222 -23.0164  EA 18 00 58.7 ...   0   0      1 10.20   T
270.337500 -23.000556 -23.0165 COM 18 01 21.0 ...   0   0    819 11.20   T
270.442917 -23.020000 -23.0166 UNK 18 01 46.3 ...   0   0    816 14.00
270.474167 -23.028889 -23.0167 COM 18 01 53.8 ...   1   0    819 11.60   T
271.357083 -23.005556 -23.0168 ELS 18 05 25.7 ...   0   0    252    --   T
271.357083 -23.005556 -23.0168  OB 18 05 25.7 ...   0   0    393  9.70   T
Length = 46887 rows

Let’s create a MOC from the coordinates of this table

moc = MOC.from_lonlat(
    table["_RAJ2000"].T * u.deg,
    table["_DEJ2000"].T * u.deg,
    max_norder=6,
)

fig = plt.figure(figsize=(9, 5))

galactic_wcs = WCS(
    {
        "naxis": 2,
        "naxis1": 1620,
        "naxis2": 810,
        "crpix1": 810.5,
        "crpix2": 405.5,
        "cdelt1": -0.2,
        "cdelt2": 0.2,
        "ctype1": "GLON-AIT",
        "ctype2": "GLAT-AIT",
    },
)

ax = fig.add_subplot(1, 1, 1, projection=galactic_wcs, frame_class=EllipticalFrame)

moc.fill(
    ax=ax,
    wcs=galactic_wcs,
    edgecolor="teal",
    facecolor="orange",
    linewidth=1.0,
    fill=True,
    alpha=0.8,
)
moc.border(ax=ax, wcs=galactic_wcs, color="k")

ax.grid(visible=True)