This page documents the columns of the lightcurve data tables exposed by the daschlab analysis toolkit. Different data sources (e.g. the “Cannon” data access portal) may use different names or expose somewhat different sets of data.
The essential columns are:
time, the time associated with the lightcurve point (HJD midpoint)magcal_magdep, the best calibrated magnitude (band depends on refcat choice)magcal_local_rms, the best uncertainty estimate onmagcal_magdeplimiting_mag_local, the limiting magnitude of the plate at the source position; for nondetections, this is the lower limit on the source magnitude. (You might colloquially call this an “upper limit”, but fainter magnitudes are larger numbers, after all.)
Columns by Category
Some columns are listed in multiple sub-sections here, if appropriate.
Identity
| Name | Unit/Type | Description |
|---|---|---|
local_id | nonnegative integer | A unique number identifying this lightcurve point |
sxt_number | positive integer | The SExtractor source identifier (NUMBER column) |
Astrometry
| Name | Unit/Type | Description |
|---|---|---|
drad_rms2 | arcsec per bin | RMS positional error per smoothing bin |
pos | Astropy SkyCoord | The fitted source position in this image |
When a lightcurve is exported, the pos column may need to be broken into
individual columns. In this case you will instead see:
| Name | Unit/Type | Description |
|---|---|---|
ra_deg | deg | The RA encoded in pos |
dec_deg | deg | The declination encoded in pos |
Data Quality
| Name | Unit/Type | Description |
|---|---|---|
aflags | bit flags | DASCH photometric data quality flags |
a2flags | bit flags | “Additional AFLAGS” |
bflags | bit flags | DASCH photometric data processing flags |
b2flags | bit flags | “Additional BFLAGS” |
drad_rms2 | arcsec per bin | RMS positional error per smoothing bin |
local_bin_reject_flag | bit flags | Data quality flags associated with the “local bin” calibration |
plate_quality_flag | bit flags | Data quality flags associated with plate-level metrics |
reject | bit flags | Flags that you set to mark points as rejected |
Source Image
| Name | Unit/Type | Description |
|---|---|---|
background | counts | Background level at the source position (SExtractor BACKGROUND column) |
ellipticity | real number | Ellipticity of source image (SExtractor ELLIPTICITY column) |
fwhm_image | pixels | FWHM of source image assuming Gaussianity (SExtractor FWHM_IMAGE column) |
fwhm_world | deg | FWHM of source image assuming Gaussianity (SExtractor FWHM_WORLD column) |
image_x | pixels | X coordinate of the isophotal image centroid (SExtractor X_IMAGE column) |
image_y | pixels | Y coordinate of the isophotal image centroid (SExtractor Y_IMAGE column) |
iso_area_world | deg² | Area of the isophotal source image (SExtractor ISOAREA_WORLD column) |
kron_radius | real number | Kron radius (SExtractor KRON_RADIUS column) |
plate_dist | deg | Distance of the source from the plate center |
theta_j2000 | deg | Orientation of source image ellipse, East from North (SExtractor THETA_J2000 column) |
sxt_iso0 | integer pixels² | Source image isophotal area at threshold level 0 (SExtractor ISOAREA_IMAGE columns?) |
sxt_iso1 | integer pixels² | Source image isophotal area at threshold level 1 (SExtractor ISOAREA_IMAGE columns?) |
sxt_iso2 | integer pixels² | Source image isophotal area at threshold level 2 (SExtractor ISOAREA_IMAGE columns?) |
sxt_iso3 | integer pixels² | Source image isophotal area at threshold level 3 (SExtractor ISOAREA_IMAGE columns?) |
sxt_iso4 | integer pixels² | Source image isophotal area at threshold level 4 (SExtractor ISOAREA_IMAGE columns?) |
sxt_iso5 | integer pixels² | Source image isophotal area at threshold level 5 (SExtractor ISOAREA_IMAGE columns?) |
sxt_iso6 | integer pixels² | Source image isophotal area at threshold level 6 (SExtractor ISOAREA_IMAGE columns?) |
sxt_iso7 | integer pixels² | Source image isophotal area at threshold level 7 (SExtractor ISOAREA_IMAGE columns?) |
Photometry
| Name | Unit/Type | Description |
|---|---|---|
magcal_magdep | mag | Calibrated magnitude after LOWESS, local, and magnitude-dependent calibration. Use this value. |
magcal_local_rms | mag | Uncertainty in magcal_local; preferred by legacy tools for magcal_magdep too — why?? |
limiting_mag_local | mag | Locally corrected limiting magnitude for source detection |
extinction | mag | Local extinction estimate from the photometric calibration process |
flux_iso | counts | Isophotal flux (SExtractor FLUX_ISO column) |
flux_max | counts | Peak flux above the background (SExtractor FLUX_MAX column) |
mag_aper | uncalibrated mag | Circular aperture magnitude (which one??) (SExtractor MAG_APER(?) columns) |
mag_auto | uncalibrated mag | “Kron-like” aperture magnitude (SExtractor MAG_AUTO column) |
mag_iso | uncalibrated mag | Isophotal magnitude (SExtractor MAG_ISO column) |
magcal_iso | mag | Calibrated isophotal magnitude after LOWESS process |
magcal_iso_rms | mag | Error in the LOWESS fit |
magcal_local | mag | Calibrated magnitude after LOWESS and “local calibration” |
magcal_local_error | mag | RMS of the needed median magnitude correction in the “local calibration” process |
magcor_local | mag | Median magnitude correction needed in the “local calibration” region |
magcal_magdep_rms | mag | Uncertainty in magcal_magdep; why do legacy tools not use this?? |
Timing
| Name | Unit/Type | Description |
|---|---|---|
time | Astropy Time | HJD midpoint of the exposure time. |
time_accuracy | days | Estimated accuracy of time. |
Catalog Match Information
| Name | Unit/Type | Description |
|---|---|---|
blended_mag | mag | Effective combined magnitude of refcat objects covered by this source |
catalog_dec | deg | Catalog star declination, precessed to plate’s epoch |
catalog_ra | deg | Catalog star right ascension, precessed to plate’s epoch |
gsc_bin_index | nonnegative integer | Spatial index value based on GSC binning; needed by some low-level APIs |
pm_dec | mas/yr | Cataloged source proper motion in declination |
pm_ra_cosdec | mas/yr | Cataloged source proper motion in right ascension, including cos(δ) term |
Plate / Exposure Identification
| Name | Unit/Type | Description |
|---|---|---|
expnum | nonnegative integer | The exposure number that this detection comes from |
mosnum | nonnegative integer | The mosaic number of the FITS file used for analysis |
platenum | nonnegative integer | The number of the plate |
plate_local_id | nonnegative integer | The “local ID” of the matched plate in the daschlab plates table |
series | short string | The lowercase series name of the plate |
series_id | nonnegative integer | A small internal integer corresponding to series |
solnum | nonnegative integer | The WCS solution number corresponding to expnum |
Calibration Pipeline Information
See also “data quality” and “photometry”.
| Name | Unit/Type | Description |
|---|---|---|
dasch_mask_index | positive integer | Index of the mask file used for pipeline defect processing |
dasch_photdb_version_id | positive integer | Internal version number of the binary photometry record |
dasch_plate_version_id | positive integer | Internal version number of the plate photometry record |
local_bin_index | nonnegative integer | Bin number used in the “local calibration” |
magdep_bin | nonnegative integer | Bin number used in the magnitude-dependent calibration |
npoints_local | nonnegative integer | Number of stars used for the median magnitude correction in “local calibration” |
spatial_bin | integer between 1 and 9 (inclusive) | Annular ring number for the “spatial” calibration |
Detailed Column Information (Alphabetical)
aflags
- Synopsis: DASCH photometric data quality flags
- Units/type: bit field
- Available for nondetections: no
FIXME: not yet documented here; see associated remarks in the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
a2flags
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
background
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
bflags
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see associated remarks in the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
b2flags
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
blended_mag
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
“For case B and BD objects, the effective magnitude of all of the GSC2.3.2 objects within the blend.”
catalog_dec
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
This is dec_2 in the legacy data terminology.
catalog_ra
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
This is ra_2 in the legacy data terminology.
dasch_mask_index
- Synopsis:
- Units/type:
- Available for nondetections: yes
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
dasch_photdb_version_id
- Synopsis:
- Units/type:
- Available for nondetections: yes
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
dasch_plate_version_id
- Synopsis:
- Units/type:
- Available for nondetections: yes
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
drad_rms2
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
ellipticity
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
expnum
- Synopsis:
- Units/type:
- Available for nondetections: yes
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
extinction
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see associated remarks in the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
flux_iso
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
flux_max
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
fwhm_image
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
fwhm_world
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
gsc_bin_index
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
image_x
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
image_y
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
iso_area_world
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
kron_radius
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
limiting_mag_local
- Synopsis:
- Units/type:
- Available for nondetections: yes
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
local_bin_index
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
local_bin_reject_flag
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see associated remarks in he Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
local_id
- Synopsis:
- Units/type:
- Available for nondetections: yes
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
mag_aper
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
mag_auto
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
mag_iso
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
magcal_iso
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
magcal_iso_rms
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
magcal_local
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
magcal_local_error
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
magcal_local_rms
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see associated remarks in the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
magcal_magdep
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
magcal_magdep_rms
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
magcor_local
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
magdep_bin
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
mosnum
- Synopsis:
- Units/type:
- Available for nondetections: yes
FIXME: not yet documented here; see associated remarks in the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
npoints_local
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
plate_dist
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
plate_local_id
- Synopsis:
- Units/type:
- Available for nondetections: yes
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
plate_quality_flag
- Synopsis:
- Units/type:
- Available for nondetections: yes
FIXME: not yet documented here; see associated remarks in the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
platenum
- Synopsis:
- Units/type:
- Available for nondetections: yes
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
pm_dec
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
pm_ra_cosdec
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
pos
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
reject
- Synopsis:
- Units/type:
- Available for nondetections: yes
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
series
- Synopsis:
- Units/type:
- Available for nondetections: yes
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
series_id
- Synopsis:
- Units/type:
- Available for nondetections: yes
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
solnum
- Synopsis:
- Units/type:
- Available for nondetections: yes
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
spatial_bin
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
sxt_iso0
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
sxt_iso1
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
sxt_iso2
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
sxt_iso3
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
sxt_iso4
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
sxt_iso5
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
sxt_iso6
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
sxt_iso7
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
sxt_number
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
theta_j2000
- Synopsis:
- Units/type:
- Available for nondetections: no
FIXME: not yet documented here; see the Legacy Data Guide. If you’re reading this, try inquiring on the DASCH Astrophysics email list!
time
- Synopsis: HJD midpoint of the exposure time
- Unit/type: Astropy Time
- Available for nondetections: yes
The time column is guaranteed to always give the best available time for the
lightcurve point in question. It is the HJD midpoint of the exposure time. When
using daschlab, this column is stored as an Astropy Time quantity, so
it is easy to convert to other date formats.
TODO: figure out and specify what timescale we're talking about!
time_accuracy
- Synopsis: Estimated uncertainty on
time. - Unit/type: days
- Available for nondetections: no
DASCH lightcurve timestamps must be determined from transcriptions of the hand-written observing logbooks, so they are subject to errors. The DASCH pipeline assesses the self-consistency of various observing parameters to check whether the transcribed timestamp “makes sense” and assigns a value for this column based on the results.
Because DASCH’s timestamps derive from these hand-written records, the best possible accuracy with which they should be trusted is a few minutes. This is comparable to the precision achievable with HJDs in an unspecified timescale (Eastman et al., 2010).
Column Subsets
“Medium” Columns
A “medium”-width lightcurve table is defined to contain only the following columns:
timemagcal_magdeplimiting_mag_localpos(orra_deganddec_deg)fwhm_worldellipticitytheta_j2000iso_area_worldaflagsbflagsplate_quality_flaglocal_bin_reject_flagseriesplatenummosnumsolnumexpnumimage_ximage_ymagcal_local_rmsmagcal_local_errordrad_rms2extinctionmagcor_localblended_magnpoints_localbackgroundfwhm_imagekron_radiustime_accuracycatalog_racatalog_decpm_ra_cosdecpm_decplate_dist