about.md

Turns a FITS binary table of Gaia DR3 stars with $m_G\leq8$ into a pseudo-tetra3-style database of stars with $m_V\leq7$.

gaia_database.py

import numpy as np
import pandas as pd
from astropy.io import fits

fits_file_path = "gaiadr3_gmag8.fits.gz"

with fits.open(fits_file_path) as f:
    hdr = f[1].header
    tbl = f[1].data

GminusV = lambda BP, RP: -0.01760 - 0.006860*(BP-RP) - 0.1732*(BP-RP)**2 # https://gea.esac.esa.int/archive/documentation/GDR2/Data_processing/chap_cu5pho/sec_cu5pho_calibr/ssec_cu5pho_PhotTransf.html
Vmag = tbl.Gmag - GminusV(tbl.BPmag, tbl.RPmag) # V = G - (G - V)

ra, dec = np.deg2rad(tbl.RA_ICRS), np.deg2rad(tbl.DE_ICRS) # ICRS coords are at epoch 2016.0

star_table = np.column_stack((ra, dec, np.cos(ra)*np.cos(dec), np.sin(ra)*np.cos(dec), np.sin(dec), Vmag))
star_catalog_IDs = pd.Series(tbl.DR3Name).str.replace("Gaia DR3 ", "").to_numpy(dtype=np.uint64)
props_packed = np.array(("gaiadr3"), dtype=[("star_catalog", "U64")])

to_save = dict(star_catalog_IDs = star_catalog_IDs[Vmag<=7.0],
               star_table = star_table[Vmag<=7.0, :],
               props_packed = props_packed)
np.savez_compressed("gaiadr3_mag7_stars.npz", **to_save)

gaiadr3_gmag8.fits.gz

gaiadr3_mag7_stars.npz

tap_query.adql