sky_calculations.py

def sky_frac(beam_size):
    """
    Calculate which fraction of the sky a beam covers

    Args:
        beam_size (float): In square degrees
    Returns:
        frac (float): Fraction of the sky that the beam covers
    """
    full_sky = (360)**2 / math.pi
    frac = beam_size/full_sky
    return frac

def sky_area(d_min, d_max, r_min, r_max):
    """
    Calculate the area of a patch in the sky

    Args:
        d_min (float): Minimum declination [deg]
        d_max (float): Maximum declination [deg]
        r_min (float): Minimum right ascension [deg]
        r_max (float): Maximum right ascension [deg]
    Returns:
        area (float): Size of area [deg**2]
    """

    d_min = math.radians(d_min)
    d_max = math.radians(d_max)
    r_min = math.radians(r_min)
    r_max = math.radians(r_max)

    # Calculate fractional surface area
    def frac(d_min, d_max, r_min, r_max):
        return (-math.cos(d_max)+math.cos(d_min))*(r_max-r_min)/(4*math.pi)

    if d_min < 0:
        top = frac(0, d_max, r_min, r_max)
        bottom = frac(0, abs(d_min), r_min, r_max)
        f = top + bottom
    else:
        f = frac(d_min, d_max, r_min, r_max)

    # Covert to square degrees
    full_sky = (360)**2 / math.pi
    area = f * full_sky

    return area


def test_sky_frac(self):
    frac = go.sky_frac(41253)
    self.assertTrue(abs(frac-1) < 0.01)