## Calibrating Wavelength with Iodine DataIn order to calibrate, the data collected by HIRES with the Iodine cell in place had to be compared to laboratory measurements of the Iodine spectrum. Each pixel on the HIRES camera is associated with a particular wavelength. Due to the complicated path light travels inside the telescope and the digitized binning determined by the number of camera pixels, the data is not perfectly precise. Since the laboratory Iodine measurements are more precise than the resolution of HIRES, their wavelengths are shifted to fit the data of HIRES with the Iodine cell. These shifts are subtracted from the wavelengths of the HIRES data for each individual run and Echelle order. For an in-depth look into the process of calculating the wavelength shifts, check out Jonathan's writeup on Iodine Calibration. |

## Smoothing the CalibrationsTo find the wavelength shift, Jonathan's convolution program sampled over several HIRES data points to produce one calibration point. Through this use of sampling Jonathan also derived the error in the calibrations. The function describing the calibration is far from analytic and requires a numerical approximation to correlate data points with the proper shift. Without a continuous line to describe the calibration there is no way to find precisely how much to shift the HIRES data. Utilizing the error to weight the calibration points, a cubic spline is used to fit a smooth line to these points. Though each calibration shift corresponds to several HIRES data points, this fitted line provides the ability to find shifts that correspond to each individual HIRES data point. |

## Looking For Trends in the Calibration DataIt is clear from the above image that the calibration shifts are spread out yet they appear to be well grouped for each run. While each individual run is precise, there is a non-negligible shift from one run to the next. There also appears to be a trend for runs performed on the same day but how much and why it varies has not been determined as of yet. It appears feasible to increase the precision of the Thorium-Argon data by utilizing the Iodine runs for that day. For instance Run 3-0 can be calibrated by Run 3-1 & 3-2 data as Run 5-1 can be calibrated by Run 5-0 & 5-3. By looking at the expandable "Table of Runs", the scheme of the runs should easily be understood. |

## Calibrate Thorium-Argon w/ IodineAs shown above, there is a definite trend within the calibration data with respect to day and Echelle order. For days 3 & 4, the first and last measurements use Thorium- Argon whereas the two in-between use Iodine (i.e. 3-1 & 3-2). On day 5, the first and fourth measurements use Iodine (i.e. 5-0 & 5-3) with Thorium-Argon used second, third, and fifth (see the above Table of Runs). The grouping of data appears to be determined by the order in which each run is measured as shown by the fact that days 3 & 4 have tightly grouped data and day 5 has a wider gap. In order to calibrate the Thorium-Argon Data, we created a template and adjusted it for each individual day and order as described in the graph to the side. |

## Remove the Iodine lines from the Iodine data## Work in ProgressAnother solution is to use the calibrated Iodine data by removing the Iodine lines to show the "naked" absorption lines. There are a few questions that need to be analyzed first. Do the absorption lines and Iodine lines simply add linearly or is it a higher order process? How do we create a template of sorts to subtract off the Iodine lines? My naive intuition is that they do not simply add but that the linear term still dominates, making it a reasonable approximation. To perform the removal, the Iodine runs should first be splined correctly and then calibrated |