wyj/GR-raytracing
1
0 Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
Files
04611e3e5ac87f8fd81bb23c304acf54f0ae9ff2
GR-raytracing/assets/2mass
T
History
wyj b0fdf1faca Output: default to PNG with PPM fallback
2026-08-27 04:25:45 -04:00
..
processed
Output: default to PNG with PPM fallback
2026-08-27 04:25:45 -04:00
raw
init
2026-08-25 22:45:43 -04:00
README.md
Add resumable all-sky 2MASS acquisition
2026-08-26 20:04:08 -04:00

README.md

2MASS Point Source Catalog sample

raw/2mass_psc_m31_0p5deg.tbl is an unmodified IPAC ASCII-table response from the NASA/IPAC Infrared Science Archive (IRSA) Gator service, drawn from the 2MASS All-Sky Point Source Catalog (PSC).

It is a circular field of view centred on M31:

  • Centre: ICRS/J2000 RA 10.6847083 deg, Dec +41.2687500 deg
  • Cone radius: 0.5 deg
  • Retrieved rows: 9,047
  • Retrieval date: 2026-08-25 (recorded in the table header)

The all-sky PSC has hundreds of millions of entries, so it is deliberately not vendored. This real-survey slice keeps the repository lightweight while providing a reproducible replacement for the synthetic latitude/longitude grid. Run bash scripts/download_2mass_psc_m31.sh from any directory to refresh it.

The table preserves the service response. Its relevant source fields are:

Field Meaning
ra, dec ICRS/J2000 right ascension and declination, in degrees
j_m, h_m, k_m 2MASS J, H, and Ks default magnitudes, in mag
dist Angular distance from the stated field centre, in arcsec
rd_flg Per-band source/read flag needed to interpret the default magnitudes

j_m, h_m, and k_m may be null in the original PSC. No temperature is included or inferred: the PSC provides photometry, not source temperatures. Do not treat magnitudes as linear fluxes without applying the appropriate 2MASS band zero points.

processed/2mass_psc_m31_0p5deg_stars.csv is generated from the raw table by python3 scripts/process_2mass_psc.py. It retains only ra_deg, dec_deg, temperature_K, and amplitude_sr. See its directory README for the fitting model and quality cut.

raw/2mass_psc_m44_1p0deg.tbl is the corresponding unmodified 1.0-degree cone around M44 (Beehive/Praesepe), centred on ICRS/J2000 RA 129.99165 deg and Dec +19.54139 deg. It contains 8,790 retrieved PSC rows (2026-08-25) and is downloaded by bash scripts/download_2mass_psc_m44.sh; process it with:

python3 scripts/process_2mass_psc.py \
  --input assets/2mass/raw/2mass_psc_m44_1p0deg.tbl \
  --output assets/2mass/processed/2mass_psc_m44_1p0deg_stars.csv

The resulting M44 CSV contains 7,802 sources after the documented three-band photometry and rd_flg selection.

Full-sky acquisition

scripts/download_2mass_psc_all_sky.py provides a resumable full-sky acquisition without asking IRSA for a cone larger than 1 degree. Inspect its storage plan before starting the long download:

python3 scripts/download_2mass_psc_all_sky.py --plan
python3 scripts/download_2mass_psc_all_sky.py --download --workers 2

It covers each latitude band with integer-RA cone sectors, wider at high latitudes, while outputs are cleaned and retained by unique 1-degree RA/Dec ownership cells. Cone overlap cannot create duplicate stars. Temporary raw tables and cleaning intermediates are stored under /tmp/2mass_psc_all_sky/ and deleted after each successful cover. The generated full-sky catalogue has one CSV per ownership cell under processed/all_sky/, named tile_raRRR_decDDD.csv. RRR is floor(RA_deg mod 360) and DDD is min(179, floor(Dec_deg + 90)); the corresponding range is [RRR, RRR+1) x [DDD-90, DDD-89) degrees. It is intentionally not a single CSV because that would duplicate a roughly 15--17 GiB result during merging. See that directory's README for restart and raw-retention behavior.

Provenance: IRSA Gator program interface, 2MASS PSC column descriptions.

Reference in new issue View Git Blame Copy Permalink