REG files are written by stella. Stella writes out a REG files for each image in which stella successfully correlates stars. REG files contain information about the pixel/line locations of stars in images and camera information. The REG file list the CX CY CZ that you solved for, the predicted CX CY CZ, and then lists information for each star on a separate line. The REG files are used by distortion to compute an updated camera model, which can then be used in INIT_LITHOS and make_sumfiles.txt. REG files live in the REGFILES directory, which is parallel to LMKFILES, SUMFILES, etc.
If a .REG file already exists, stella will use that information as a starting point when you re-run stella. If you want to start an image totally afresh, you must delete the pre-existing .REG file.
Warning! If you have an existing REG file and then re-run the image through stella and do NOT solve for pointing, stella will delete the existing REG file!
Stella names REG files as PICNAME.REG.
An annotated .REG file
-0.9303361 -0.1242768 0.3450073 -0.9302355 -0.1243779 0.3452419 Cx, C0x --> The solved-for Cx and the predicted Cx. 0.3498056 -0.5830977 0.7332347 0.3500547 -0.5830538 0.7331507 Cy, C0y --> The solved-for Cy and the predicted Cy. 0.1100489 0.8028402 0.5859496 0.1101069 0.8028564 0.5859164 Cz, C0z --> The solved-for Cz and the predicted Cz. 0.1078023 0.8029705 0.5861886 1005.233 696.014 -0.092 0.073 150822 W PX LN dx dy catno --> each line in this section of the REG file . corresponds to a star. The columns are . a unit vector to the star (first three columns), . the pixel/line location of the star in the image . (next two columns), and then the pixel/line residuals etc., one line in the file for each star that correlated in the image for the star (next two columns), and star catalog number (last column) END 39 -0.014 0.067 -0.266 0.316 2628.33430 --> The last line of the file says how many stars exceeded the correlation limit (39, in this case). The next three numbers are the rotation about the X, Y, and Z axes in units of milliradians. The Z-axis rotation is a twist. The second-to-last entry is the RMS pixel residual between predicted and observed star locations. The last term is the focal length in mm solved from this image.