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from builtins import object 

import numpy 

 

__all__ = ["LSSTdefaults"] 

 

class LSSTdefaults(object): 

""" 

This class exists to store default values of seeing, m5, and gamma taken from the over 

view paper (arXiv 0805.2366, Table 2, 29 August 2014 version) 

""" 

 

def __init__(self): 

# Standard FWHMeffective in arcseconds 

self._FWHMeff = {'u':0.92, 'g':0.87, 'r':0.83, 'i':0.80, 'z':0.78, 'y':0.76} 

# Expected effective wavelength for throughput curves, in nanometers 

self._effwavelen = {'u':367.0, 'g':482.5, 'r':622.2, 'i':754.5, 'z':869.1, 'y':971.0} 

# Expected m5 depths (using FWHMeffective + dark sky + X=1.2 atmosphere + throughput curves) 

self._m5 = {'u':23.68, 'g':24.89, 'r':24.43, 'i':24.00, 'z':24.45, 'y':22.60} 

self._gamma = {'u':0.037, 'g':0.038, 'r':0.039, 'i':0.039, 'z':0.040, 'y':0.040} 

 

 

def m5(self, tag): 

""" 

From arXiv 0805.2366 (Table 2): 

 

Typical 5-sigma depth for point sources at zenith, assuming 

exposure time of 2 x 15 seconds and observing conditions as listed. 

Calculated using $SYSENG_THROUGHPUT curves as of 11/25/2015, using 

$SYSENG_THROUGHPUT/python/calcM5.py 

 

@param [in] the name of a filter i.e. 'u', 'g', 'r', 'i', 'z', or 'y' 

 

@param [out] the corresponding m5 value 

""" 

return self._m5[tag] 

 

 

def FWHMeff(self, tag): 

""" 

From arXiv 0805.2366 XXX version (Table 2): 

 

The expected FWHMeff in arcseconds. This is the width of a single gaussian 

which produces the appropriate number of effective pixels in the PSF (thus 'FWHMeff'). 

This is the value to use for calculating Neffective, when Neffective assumes a single gaussian. 

It can be converted to a geometric FWHM (equivalent to the approximate value which would 

be measured across a van Karmen PSF profile) using SignalToNoise.FWHMeff2FWHMgeom. 

 

@param [in] the name of a filter i.e. 'u', 'g', 'r', 'i', 'z', or 'y' 

 

@param [out] the corresponding FWHMeff 

""" 

 

return self._FWHMeff[tag] 

 

def effwavelen(self, tag): 

""" 

From the throughput curves in syseng_throughputs, calculated by 

$SYSENG_THROUGHPUTS/python/effectiveWavelen.py 

as of 11/25/2015. 

""" 

return self._effwavelen[tag] 

 

 

def gamma(self, tag): 

""" 

See Table 2 and Equaiton 5 of arXiv 0805.2366 29 August 2014 version. 

 

@param [in] the name of a filter i.e. 'u', 'g', 'r', 'i', 'z', or 'y' 

 

@param [out] the corresponding value of gamma as defined in the 

reference above 

""" 

 

return self._gamma[tag]