Perform background subtraction when calculating instrument magnitude

[outyprouty]

The current top-of-telescope calibration pipeline that allows us to calculate an instrument magnitude is not accounting for the background sky intensity in the neighborhood of the sources. We estimate this background in the 1-D Gaussian Fit of the radial profile extracted from the subframe around the source.

[chiariniolivia]

at the moment, something about us just subtracting the constant offset doenst work. we need to find a more robust way to remove the background from our calibrated frames.

[chiariniolivia]

12 is likely to resolve this issue as well, since 0s and negatives are the cause of that as well. Once a consistent design decision is made and written down, we should be able to close both of these issues.