Understanding your results

Every query returns an astropy Table. Rather than face the full schema, here are the kinds of columns a science user actually reaches for, grouped by what they tell you. Archives share many column names, but not all; the table at the end maps the ones that differ, and each archive’s page lists its common columns. For the authoritative, complete list of any table — with units and descriptions — call describe_table, e.g. describe_table('neidl2').

Identity and time

object — the free-text target name the observer entered ('HD 189733', or 'Sun'). Good for a sanity check, not for exact matching.
qobject — the normalized catalog ID (typically Gaia DR2); the clean exact-match key.
obsdate — the observation time stamp; the column behind query_datetime.
obsjd, mjd, ccfjdsum — precise numeric times (Julian Date (JD / MJD)) for building an RV time series and orbital fits.

The RV answer

The radial velocity and its error bar. See Radial velocities and the CCF for what they mean, and the table below for each archive’s column names.

Quality and conditions

exptime — exposure time in seconds; a common selection filter.
airmass — atmosphere traversed (1.0 = overhead); a conditions proxy.
seeing — atmospheric blur in arcsec; smaller is better.
extsnr — extracted signal-to-noise; a natural quality cut.
dvrms — the photon-limited RV precision predicted for the exposure.

Provenance

program — the proposal ID the data was taken under.
The PI (Principal Investigator) or observer.
swversion, l2procversion — the pipeline version (swversion / procversion); pin it for reproducible RV sets.

Download keys

l2filename / l2filepath (and the l0/l1 equivalents) — the filename / filepath / filehand columns. download needs them, so keep them in any columns= selection.

Column names by archive

The concepts above are shared; where archives name a column differently, this is the translation to use when porting a workflow:

Concept	NEID	EXPRES (solar)
Radial velocity	`ccfrvmod`	`v`
RV uncertainty	`ccfnoise`	`e_v`
Observation time	`obsdate`	`obsdate`
PI / observer	`piname`	`observer` (L1 only)
Catalog target ID	`qobject`	none (always the Sun)

See Querying vs downloading, and proprietary data for using the download keys.