PhotometryData

class stellarphot.PhotometryData(*args, input_data=None, colname_map=None, passband_map=None, retain_user_computed=False, **kwargs)

Bases: BaseEnhancedTable

A modified astropy.table.QTable to hold reduced photometry data that provides the convenience of validating the data table is in the proper format including units. It returns an PhotometryData which is a astropy.table.QTable with additional attributes describing the observatory and camera.

Parameters:

input_data: `astropy.table.QTable`, optional (Default: None)

A table containing all the instrumental aperture photometry results to be validated. Note: It is allowed for the ‘ra’ and ‘dec’ columns to have np.nan values, but if they do, the ‘bjd’ column will not be computed and will also be left with ‘np.nan’.

observatory: `stellarphot.settings.Observatory`, optional (Default: None)

Information about the observatory.

camera: `stellarphot.Camera`, optional (Default: None)

A description of the CCD used to perform the photometry.

colname_map: dict, optional (Default: None)

A dictionary containing old column names as keys and new column names as values. This is used to automatically update the column names to the desired names before the validation is performed.

passband_map: `stellarphot.settings.PassbandMap`, optional (Default: None)

An object containing a mapping from instrumental passband names to AAVSO passband names. This is used to automatically update the passband column to AAVSO standard names if desired. See the documentation for stellarphot.settings.PassbandMap for more information. The object behaves like a dictionary when accessing it.

retain_user_computed: bool, optional (Default: False)

If True, any computed columns (see USAGE NOTES below) that already exist in data will be retained. If False, will throw an error if any computed columns already exist in data.

Attributes:

camera: `stellarphot.Camera`

A description of the CCD used to perform the photometry.

observatory: `stellarphot.settings.Observatory`, optional (Default: None)

Information about the observatory.

Notes

For validation of inputs, you must provide camera, observatory, AND input_data, if you do not, an empty table will be returned.

To be accepted as valid, the input_data must MUST contain the following columns with the following units. The data in those columns is NOT validated, the values in those columns could be invalid. Furthermore, the ‘consistent count units’ below simply means it can be any unit, but it must be the same for all the columns with ‘consistent count units’.

Column name	Unit
star_id	None
RA	u.deg
Dec	u.deg
xcenter	u.pix
ycenter	u.pix
fwhm_x	u.pix
fwhm_y	u.pix
width	u.pix
aperture	u.pix
aperture_area	u.pix
annulus_inner	u.pix
annulus_outer	u.pix
annulus_area	u.pix
aperture_sum	consistent count units
annulus_sum	consistent count units
sky_per_pix_avg	consistent count units (per pixel)
sky_per_pix_med	consistent count units (per pixel)
sky_per_pix_std	consistent count units (per pixel)
aperture_net_cnts	consistent count units
noise_cnts	consistent count units
noise_electrons	u.electron
snr	None
mag_inst	None
mag_error	None
exposure	u.s
date-obs	astropy.time.Time with scale=’utc’
airmass	None
passband	None
file	None

In addition to these required columns, the following columns are created based on the input data during creation.

night

If these computed columns already exist in data class the class will throw an error a ValueError UNLESS ignore_computed=True is passed to the initializer, in which case the columns will be retained and not replaced with the computed values.

Attributes Summary

bjd	The barycentric julian date of the observation.
camera	Descriptor to define a custom attribute for a Table subclass.
coord	Return the coordinates of the stars in the table as a SkyCoord object.
mag_inst	Instrumental magnitude.
mag_inst_error	Error in the instrumental magnitude.
observatory	Descriptor to define a custom attribute for a Table subclass.
passband	The passband of the observations.
phot_descript

Methods Summary

add_bjd_col([observatory, bjd_coordinates])	Returns a astropy column of barycentric Julian date times corresponding to the input observations.
lightcurve_for(target[, flux_column, passband])	Return the light curve for a single star as a lightkurve.LightCurve object.
write_aavso_extended(path, **kwargs)	Write this photometry table in the AAVSO Extended File Format.

Attributes Documentation

bjd

The barycentric julian date of the observation.

camera

Descriptor to define a custom attribute for a Table subclass.

The value of the TableAttribute will be stored in a dict named __attributes__ that is stored in the table meta. The attribute can be accessed and set in the usual way, and it can be provided when creating the object.

Defining an attribute by this mechanism ensures that it will persist if the table is sliced or serialized, for example as a pickle or ECSV file.

See the MetaAttribute documentation for additional details.

Parameters:

defaultobject

Default value for attribute

Examples

>>> from astropy.table import Table, TableAttribute
>>> class MyTable(Table):
...     identifier = TableAttribute(default=1)
>>> t = MyTable(identifier=10)
>>> t.identifier
10
>>> t.meta
{'__attributes__': {'identifier': 10}}

coord

Return the coordinates of the stars in the table as a SkyCoord object. This is computed from the ‘ra’ and ‘dec’ columns in the table.

mag_inst

Instrumental magnitude.

mag_inst_error

Error in the instrumental magnitude.

observatory

Descriptor to define a custom attribute for a Table subclass.

The value of the TableAttribute will be stored in a dict named __attributes__ that is stored in the table meta. The attribute can be accessed and set in the usual way, and it can be provided when creating the object.

Defining an attribute by this mechanism ensures that it will persist if the table is sliced or serialized, for example as a pickle or ECSV file.

See the MetaAttribute documentation for additional details.

Parameters:

defaultobject

Default value for attribute

Examples

>>> from astropy.table import Table, TableAttribute
>>> class MyTable(Table):
...     identifier = TableAttribute(default=1)
>>> t = MyTable(identifier=10)
>>> t.identifier
10
>>> t.meta
{'__attributes__': {'identifier': 10}}

passband

The passband of the observations.

phot_descript = {'airmass': None, 'annulus_area': Unit("pix"), 'annulus_inner': Unit("pix"), 'annulus_outer': Unit("pix"), 'annulus_sum': None, 'aperture': Unit("pix"), 'aperture_area': Unit("pix"), 'aperture_net_cnts': None, 'aperture_sum': None, 'date-obs': None, 'dec': Unit("deg"), 'exposure': Unit("s"), 'file': None, 'fwhm_x': Unit("pix"), 'fwhm_y': Unit("pix"), 'mag_error': None, 'mag_inst': None, 'noise_cnts': None, 'noise_electrons': Unit("electron"), 'passband': None, 'ra': Unit("deg"), 'sky_per_pix_avg': None, 'sky_per_pix_med': None, 'sky_per_pix_std': None, 'snr': None, 'star_id': None, 'width': Unit("pix"), 'xcenter': Unit("pix"), 'ycenter': Unit("pix")}

Methods Documentation

add_bjd_col(observatory=None, bjd_coordinates=None)

Returns a astropy column of barycentric Julian date times corresponding to the input observations. It modifies that table in place.

Parameters:

observatory: `stellarphot.settings.Observatory`

Information about the observatory. Defaults to the observatory in the table metadata.

bjd_coordinates: `astropy.coordinates.SkyCoord`, optional (Default: None)

The coordinates to use for computing the BJD. If None, the RA and Dec columns in the table will be used.

lightcurve_for(target, flux_column='mag_inst', passband=None)

Return the light curve for a single star as a lightkurve.LightCurve object. One of the parameters star_id, coordinates or name must be specified.

Parameters:

targetstr, int, or astropy.coordinates.SkyCoord

The target star. This can be a star_id, a SkyCoord object, or a name that can be resolved by astropy.coordinates.SkyCoord.from_name.

flux_columnstr, optional

The name of the column to use as the flux. Default is ‘mag_inst’. This need not actually be a flux.

passbandstr, optional

The passband to use to generate the lightcurve for. This is only needed if there is more that one passband in the data.

Returns:

lightkurve.LightCurve

The light curve for the star. This includes all of the columns in the stellarphot.`PhotometryData object and columns time, flux, and flux_err.

write_aavso_extended(path, **kwargs)

Write this photometry table in the AAVSO Extended File Format.

See stellarphot.io.write_aavso_extended for the full signature and behavior. All keyword arguments are forwarded to that function.