Calculate chi-squared between model and observed spectra

[djperrefort]

We can calculate the chi-squared value between our models and DR2 spectroscopy. I imagine the general steps for this include:

• Color-warping the observed spectra to account for the wavelength dependence of the flux calibration
• Using published t0 values to shift out modeled phase values to the same t=0 point as each observation
• Modeling the flux with each model at for each observed time
• Tabulating chi-squared values
• summarizing results in a few plots

The chi-squared should be calculated for the total spectrum but also for individual regions overlapping with different bandpasses. These regions can be defined as the point where the transmission drops below 10%. u-band should have a lower bound around 3200 A (It has a long blueward tail).

A major road block is that error values for the DR1 spectra are note published.

[djperrefort]

Some notes from an offline convo with @wmwv:

1. We don't care about the statistical errors on each flux value since we expect them to be significantly smaller than the error in the calibration. To be conservative, assume an error of 30% of the flux.
2. It's not clear whether we should calculate chi-sq per band, per wavelength, per wavelength window, or per feature. Lets start with per wavelength and go from there.

[wmwv]

To be conservative, assume an error of 30% of the flux.

3% of the flux.

[djperrefort]

Pinging @spletts so she has this issue for reference.