# From arxiv.org/abs/astro-ph/0701508v1
# B - g, x = g-r
# V - g, x = g-r
# R - r, x = r-i
# I - i, x = r-i
# (a_0 * x^3) + (a_1 * x^2) + (a_2 * x) + a_3
filtercode	a_0		a_1		a_2		a_3
B	+0.2628	-0.7952	+1.0544	+0.0268
V	+0.0688	-0.2056	-0.3838	-0.0534
R	-0.0107	+0.0050	-0.2689	-0.1540
I	-0.0307	+0.1163	-0.3341	-0.3584