Data levels are defined as follows:

• Level-0: Raw data from the telescope. Image data at level 0 have not been gain corrected. Spectropolarimetric modulation states have not been separated.
• Level-1: First order corrections have been applied. Imaging data has been gain-corrected and processed via speckle burst reconstruction. Spectropolarimetric data is separated into Stokes I, Q, U, and V, but significant cleaning and post-processing has not taken place. Files at level 1 may be in IDL .sav format, or other nonstandard data formats. Note that imaging data at this step may or may not have been processed via a non-flow-preserving destretch algorithm. The individual filenames will indicate whether or not this is the case.
• Level-1.5: Further post-processing has taken place. Data at level-1.5 can be considered science-ready. Imaging data has been destretched using both a method designed to preserve surface flows, as well as a method that is more stable under variable seeing conditions. Spectropolarimetric and spectroscopic data have been wavelength-calibrated and corrected for fringing. Data at level-1.5 have been repacked as FITS files
• Level-2: Level-2 data have been processed to display physical parameters, such as magnetic field data, or other inversion results. Data at level-2 may have various filetypes.

Seeing parameters are calculated from Level-0, unprocessed data, before speckle reconstruction. The "median" and +/- 1-sigma images below are calculated from the Helmli-Scherer mean (HSM) for ROSA, and the Median Filter Gradiant Similarity (MFGS) metric for Zyla. These metrics (and others, such as the RMS, and mean of the image) are calculated for the full observing day. HSM and MFGS are the most sensitive to unknown atmospheric conditions, however, the HSM is faster and tends to perform better with photospheric data, while MFGS performs better with chromospheric structures.