Due to the high spectral resolution goals (R > 2x10^4) for the upcoming Full-sun Ultraviolet Rocket Spectrograph (FURST), instrument calibration will be particularly important. The Solar Physics groups at NASA MSFC and Montana State University (MSU) have been developing the tools necessary to achieve this goal. These include improved tracking of error propagation, in-situ monitoring of the camera gain with a radioactive Fe-55 source, and even better wavelength calibration. This presentation will focus on the latter. We will highlight the development of a calibration method which uses a two-dimensional second-order polynomial to map pixels to wavelength under a simulated noisy diagnostic lamp signal. Additionally, we have introduced a tilted CCD in order to overcome the Nyquist limit. With this as the background, we have been investigating an effect known well among ground-based imaging: geocoronal absorption. We have been looking into how much this effect will be present in the atmosphere at sounding-rocket altitudes (~100-200km). Many studies have found ways to correct for these so-called “Telluric” lines. However, it may be that these lines can in fact be a useful tool to further improve our calibration, rather than simply a nuisance to be corrected for!