sky – Sky subtraction and estimation

Modules that provides utilities related with the sky background

The main products are:

pyhetdex.tools.astro.sky.fe_sky_subtraction(fname, sig=2.5, iters=None, wmin=None, wmax=None, width=20, prefix='S', skyprefix='Sky', output_both=True)[source]

Perform the sky subtraction from a fiber extracted frame

Parameters:
fname : string

name of the fits file to process

sig : float, optional

number of standard deviations to use for the clipping limit

iters : int or None, optional

number of iterations to perform clipping for, or None to clip until convergence is achieved (i.e. continue until the last iteration clips nothing).

wmin, wmax : floats, optional

maximum and minimum wavelength in Armstrong to use for the sigma clipping. Converted to indices using the ‘CRVAL1’ and ‘CDELT1’ keyword in the header of the fits file. If None the minimum and/or maximum of the range used

width : int, optional

width of the moving window used to estimate the sky background

prefix : string, optional

prefix of the sky subtracted file

skyprefix : string, optional

prefix of the sky file

output_both : bool, optional

save both sky and sky subtracted frames, instead of the latter alone
pyhetdex.tools.astro.sky.fe_sky_background(fname, **kwargs)[source]

Estimate the sky background as the (sigma clipped) median of medians within the required wavelengths and fiber number boundaries.

The input is read from fname. The keyword arguments are passed to hdu_fe_sky_background()

Parameters:
fname : string

file to average

sig : None or float, optional

if not None, ignore fibers with signal outside sig standard deviation

iters : int or None, optional

number of iterations to perform clipping for, or None to clip until convergence is achieved (i.e. continue until the last iteration clips nothing).

wmin, wmax : float, optional

minimum and maximum wavelength to consider for the average

wmin, wmax : floats, optional

maximum and minimum wavelength in Armstrong to use for the estimate. Converted to indices using the ‘CRVAL1’ and ‘CDELT1’ keyword in the header of the fits file. If None the minimum and/or maximum of the range used

fibmin, fibmax : float, optional

minimum and maximum fiber number to consider
Returns:
median : float

average

n_fibs : int

number of fibers used for the final median
pyhetdex.tools.astro.sky.hdu_fe_sky_background(data, header, sig=2.5, iters=None, wmin=None, wmax=None, fibmin=None, fibmax=None)[source]

Estimate the sky background as the (sigma clipped) median of medians within the required wavelengths and fiber number boundaries

Parameters:
data : numpy ndarray

data of the fits image

header : astropy.io.fits.Header instance

header of the fits image

sig : None or float, optional

if not None, ignore fibers with signal outside sig standard deviation

iters : int or None, optional

number of iterations to perform clipping for, or None to clip until convergence is achieved (i.e. continue until the last iteration clips nothing).

wmin, wmax : float, optional

minimum and maximum wavelength to consider for the average

wmin, wmax : floats, optional

maximum and minimum wavelength in Armstrong to use for the estimate. Converted to indices using the ‘CRVAL1’ and ‘CDELT1’ keyword in the header of the fits file. If None the minimum and/or maximum of the range used

fibmin, fibmax : float, optional

minimum and maximum fiber number to consider
Returns:
median : float

average

n_fibs : int

number of fibers used for the final median
pyhetdex.tools.astro.sky.moving_window(mask, cindex, width=20)[source]

Modify the mask to exclude rows outside the mask

Parameters:
mask : 1d array of bool

mask across with the window moves

cindex : int

central index of the window

width : int, optional

maximum width of the window. Edges are not wrapped around
Returns:
window_mask : 1d array of bool

mask with all the elements outside the window set to False