# Response curves taken from:
# http://www.sdss.org/wp-content/uploads/2017/04/filter_curves.fits
# 
# Extracted data are the 'wavelength' and 'respt' columns in each
# extension.  The wavelengths are assumed to be in vacuum.
#
# From the header of the fits file:
#-----------------------------------------------------------------------
# 
# The following file is from Jim Gunn, from June 2001.  It should be
# self-explanatory; for most purposes, you will want to use the second
# column.  Consider this file preliminary.
#
# These filter curves have been used to calculate the effective
# wavelengths and the qtdl/l (see Chapter 8 of the Black Book) of the
# filters; the values are:
#
# u 3551 0.0171
# g 4686 0.0893
# r 6166 0.0886
# i 7480 0.0591
# z 8932 0.0099
#
# Table Caption For Response Functions
# 
# The first column is the wavelength in \AAngstroms.
# 
# The second column (respt) is the quantum efficiency on the sky looking
# through 1.3 airmasses at APO for a point source.
# 
# The third column (resbig) is the QE under these conditions for very
# large sources (size greater than about 80 pixels) for which the
# infrared scattering is negligible.  The only filters for which the
# infrared scattering has any effect are r and i; the scattering in the
# bluer chips is negligible, and the z chips are not thinned and the
# phenomenon does not exist.
# 
# The fourth column (resnoa) is the response of the third column with
# {\it no} atmosphere, and the fifth column is the assumed atmospheric
# transparency at {\it one} airmass at APO.
# 
# The tables were constructed using monochromator illumination of the
# camera with a bandpass of about 100 \AA, sampled for the u filter at
# 50 \AA intervals and for the others at 100 \AA intervals.  These
# measurements were compared with measured responses of the component
# filters and detectors and three additional points were interpolated
# using these data, two at the extreme toes and one additional (in g, r,
# and i) at the point of the beginning of the sharp cutoff of the
# shortpass interference filter.  These points are necessary in order to
# make spline interpolation of the response data well-behaved. These
# spline-interpolated response data were then multiplied by measured
# aluminum reflectivities and scaled atmospheric transmission to produce
# the tables below. The overall normalization is somewhat uncertain, but
# this uncertainty does not affect the shapes.  Note, however, that
# there has been no attempt to remove the finite resolution of the
# monochromator measurements. These tables are the {\it averages} of the
# responses for all six of the camera chips with a given filter. The
# responses are in general very similar except in the z band, where the
# nonuniformity of the infrared rolloff, presumably associated with
# varying thickness of the epitaxial layer or perhaps the gate
# structures in these thick devices, introduces variations in the
# effective wavelengths of the filters of order 100 \AA. We are
# currently working on better response functions and will present them
# when they become available, but these will suffice for most
# applications. In all cases the first point is a measured point, so the
# grid of wavelengths at which measurements exist is a subset of the
# wavelength lists here.  
