Atmospheric Differential Refraction¶
Welcome to the documentation for the ‘wifes_adr.py’ module, which contains the core functions for correcting atmospheric differential refraction in WiFeS data.
- pywifes.wifes_adr.adr_x_y(wavelength_array, secz, objha, objdec, tellat, teltemp, telpres, telwvp=8.0, telpa=0.0, ref_wl=5000.0)¶
Atmospheric differential refraction, based on model of Filippenko (1982PASP…94..715F).
Assumes plane-parallel atmosphere; Barrell (1951) model for dependence of index of refraction on temperature, air pressure, and water vapour pressure; and values for index of refraction at sea level from Edlen 1953 / Coleman, Bozman, & Meggers 1960.
Default water vapour pressure of 8 mm of mercury from Filippenko corresponds to _saturation_ pressure (not actual pressure) at air temperature of ~7 C, typical of average conditions for latitude of +/-30 deg and altitude of ~2000 m (Allen 1973), where the air pressure is ~600 mm of mercury.
Inputs:
wavelength_array: (vacuum) wavelengths at which to calculate the differential refraction.
secz: secant of zenith angle, equivalent to the airmass for moderate zenith angles (<60 deg).
objha: hour angle of the target in degrees.
objdec: declination of the target in degrees.
tellat: telescope latitude in degrees.
telltemp: air temperature at telescope in Celsius.
telepres: air pressure at telescope in mm of mercury.
- telwvp: water vapour pressure at telescope in mm of mercury.
Default 8 mm.
- telpa: position angle (radians East from North).
Default 0 radians.
- ref_wl: reference wavelength for the differential refraction in Angstroms.
Default 5000 A.
Outputs:
- list of [array of x-axis offsets for each wavelength, array of y-axis offsets for each wavelength].
Units of arcseconds.