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1from builtins import object 

2import numpy 

3 

4__all__ = ["LSSTdefaults"] 

5 

6class LSSTdefaults(object): 

7 """ 

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

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

10 """ 

11 

12 def __init__(self): 

13 # Standard FWHMeffective in arcseconds 

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

15 # Expected effective wavelength for throughput curves, in nanometers 

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

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

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

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

20 

21 

22 def m5(self, tag): 

23 """ 

24 From arXiv 0805.2366 (Table 2): 

25 

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

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

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

29 $SYSENG_THROUGHPUT/python/calcM5.py 

30 

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

32 

33 @param [out] the corresponding m5 value 

34 """ 

35 return self._m5[tag] 

36 

37 

38 def FWHMeff(self, tag): 

39 """ 

40 From arXiv 0805.2366 XXX version (Table 2): 

41 

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

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

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

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

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

47 

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

49 

50 @param [out] the corresponding FWHMeff 

51 """ 

52 

53 return self._FWHMeff[tag] 

54 

55 def effwavelen(self, tag): 

56 """ 

57 From the throughput curves in syseng_throughputs, calculated by 

58 $SYSENG_THROUGHPUTS/python/effectiveWavelen.py 

59 as of 11/25/2015. 

60 """ 

61 return self._effwavelen[tag] 

62 

63 

64 def gamma(self, tag): 

65 """ 

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

67 

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

69 

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

71 reference above 

72 """ 

73 

74 return self._gamma[tag]