Merge pull request #24 from james-m-osborn/master

Added parameter conversion tools

aotools/turbulence/__init__.py

@@ -2,4 +2,5 @@
 from .infinitephasescreen import *
 from .temporal_ps import *
 from .slopecovariance import *
-from .turb import *
+from .turb import *
+from .atmos_conversions import *

aotools/turbulence/atmos_conversions.py

@@ -0,0 +1,75 @@
+import numpy
+
+def cn2_to_seeing(cn2,lamda=500.E-9):
+    """
+    Calculates the seeing angle from the integrated Cn2 value
+
+    Parameters:
+        cn2 (float): integrated Cn2 value in m^2/3
+        lamda : wavelength
+
+    Returns:
+        seeing angle in arcseconds
+    """
+    r0 = cn2_to_r0(cn2,lamda)
+    seeing = r0_to_seeing(r0,lamda)
+    return seeing
+
+def cn2_to_r0(cn2,lamda=500.E-9):
+    """
+    Calculates r0 from the integrated Cn2 value
+
+    Parameters:
+        cn2 (float): integrated Cn2 value in m^2/3
+        lamda : wavelength
+
+    Returns:
+        r0 in cm
+    """
+    r0=(0.423*(2*numpy.pi/lamda)**2*cn2)**(-3./5.)
+    return r0
+
+def r0_to_seeing(r0,lamda=500.E-9):
+    """
+    Calculates the seeing angle from r0
+
+    Parameters:
+        r0 (float): Freid's parameter in cm
+        lamda : wavelength
+
+    Returns:
+        seeing angle in arcseconds
+    """
+    return (0.98*lamda/r0)*180.*3600./numpy.pi
+
+def coherenceTime(cn2,v,lamda=500.E-9):
+    """
+    Calculates the coherence time from profiles of the Cn2 and wind velocity
+
+    Parameters:
+        cn2 (array): Cn2 profile in m^2/3
+        v (array): profile of wind velocity, same altitude scale as cn2 
+        lamda : wavelength
+
+    Returns:
+        coherence time in seconds
+    """
+    Jv = (cn2*(v**(5./3.))).sum()
+    tau0=(Jv**(-3./5.))*0.057*lamda**(6./5.)
+    return tau0
+
+def isoplanaticAngle(cn2,h,lamda=500.E-9):
+    """
+    Calculates the isoplanatic angle from the Cn2 profile
+
+    Parameters:
+        cn2 (array): Cn2 profile in m^2/3
+        h (Array): Altitude levels of cn2 profile in m
+        lamda : wavelength
+
+    Returns:
+        isoplanatic angle in arcseconds
+    """
+    Jh = (cn2*(h**(5./3.))).sum()
+    iso = 0.057*lamda**(6./5.)*Jh**(-3./5.)  *180.*3600./numpy.pi
+    return iso