from __future__ import print_function
import numpy as np
from .baseStacker import BaseStacker
from lsst.sims.utils import Site
from .generalStackers import FiveSigmaStacker
__all__ = ['M5OptimalStacker', 'generate_sky_slopes']
[docs]def generate_sky_slopes():
"""
Fit a line to how the sky brightness changes with airmass.
"""
import lsst.sims.skybrightness as sb
import healpy as hp
sm = sb.SkyModel(mags=True, moon=False, twilight=False, zodiacal=False)
mjd = 57000
nside = 32
airmass_limit = 2.0
dec, ra = hp.pix2ang(nside, np.arange(hp.nside2npix(nside)))
dec = np.pi/2 - dec
sm.setRaDecMjd(ra, dec, mjd)
mags = sm.returnMags()
filters = mags.dtype.names
filter_slopes = {}
for filterName in filters:
good = np.where((~np.isnan(mags[filterName])) & (sm.airmass < airmass_limit))
pf = np.polyfit(sm.airmass[good], mags[filterName][good], 1)
filter_slopes[filterName] = pf[0]
print(filter_slopes)
[docs]class M5OptimalStacker(BaseStacker):
"""
Make a new m5 column as if observations were taken on the meridian.
If the moon is up, assume sky brightness stays the same.
Assumes seeing scales as airmass^0.6. Uses linear fits for sky and airmass relation.
Parameters
----------
airmassCol : str ('airmass')
Column name for the airmass per pointing.
decCol : str ('dec_rad')
Column name for the pointing declination.
skyBrightCol: str ('filtSkyBrightness')
Column name for the sky brighntess per pointing.
filterCol : str ('filter')
Column name for the filter name.
m5Col : str ('fiveSigmaDepth')
Colum name for the five sigma limiting depth per pointing.
moonAltCol : str ('moonAlt')
Column name for the moon altitude per pointing.
sunAltCol : str ('sunAltCol')
Column name for the sun altitude column.
site : str ('LSST')
Name of the site.
Returns
-------
numpy.array
Adds a column to that is approximately what the five-sigma depth would have
been if the observation had been taken on the meridian.
"""
colsAdded = ['m5Optimal']
def __init__(self, airmassCol='airmass', decCol='dec_rad',
skyBrightCol='filtSkyBrightness', seeingCol='FWHMeff',
filterCol='filter',
moonAltCol='moonAlt', sunAltCol='sunAlt',
site='LSST'):
self.site = Site(site)
self.units = ['mags']
self.airmassCol = airmassCol
self.decCol = decCol
self.skyBrightCol = skyBrightCol
self.seeingCol = seeingCol
self.filterCol = filterCol
self.moonAltCol = moonAltCol
self.sunAltCol = sunAltCol
self.m5_stacker = FiveSigmaStacker()
self.m5Col = self.m5_stacker.colsAdded[0]
self.colsReq = [airmassCol, decCol, skyBrightCol,
seeingCol, filterCol, moonAltCol, sunAltCol]
self.colsReq.extend(self.m5_stacker.colsReq)
self.colsReq = list(set(self.colsReq))
def _run(self, simData, cols_present=False):
simData, m5col_present = self.m5_stacker._addStackerCols(simData)
simData = self.m5_stacker._run(simData, m5col_present)
# kAtm values from lsst.sims.operations gen_output.py
kAtm = {'u': 0.50, 'g': 0.21, 'r': 0.13, 'i': 0.10,
'z': 0.07, 'y': 0.18}
# Linear fits to sky brightness change, no moon, twilight, or zodiacal components
# Use generate_sky_slopes to regenerate if needed.
skySlopes = {'g': -0.52611780327408397, 'i': -0.67898669252082422,
'r': -0.61378749766766827, 'u': -0.27840980367303503,
'y': -0.69635091524779691, 'z': -0.69652846002009128}
min_z_possible = np.abs(simData[self.decCol] - self.site.latitude_rad)
min_airmass_possible = 1./np.cos(min_z_possible)
for filterName in np.unique(simData[self.filterCol]):
deltaSky = skySlopes[filterName]*(simData[self.airmassCol] - min_airmass_possible)
deltaSky[np.where((simData[self.moonAltCol] > 0) |
(simData[self.sunAltCol] > np.radians(-18.)))] = 0
# Using Approximation that FWHM~X^0.6. So seeing term in m5 of: 0.25 * log (7.0/FWHMeff )
# Goes to 0.15 log(FWHM_min / FWHM_eff) in the difference
m5Optimal = (simData[self.m5Col] - 0.5*deltaSky -
0.15*np.log10(min_airmass_possible / simData[self.airmassCol]) -
kAtm[filterName]*(min_airmass_possible - simData[self.airmassCol]))
good = np.where(simData[self.filterCol] == filterName)
simData['m5Optimal'][good] = m5Optimal[good]
return simData