MDI Full-Disk Magnetogram Loader

Lists the dates and times (YYYYMMDD.HHMM for year YYYY, month number
MM, day number DD, hour HH, minute MM in TAI) for which MDI full-disk
magnetograms are available.  Select any of the items to load the
corresponding magnetogram into the viewer whose editable number is
listed in the "target window" box.

The "scale to Gauss" check box controls whether the raw data will be converted
to Gauss using the calibration in the file header. The file must be a FITS file
and contain the keys $BSCALE and $BZERO for this to work properly (and they
have to be correct of course). This should work for the FDMG files in this
archive. The conversion will slow down the display.

The "mask limb" check box controls whether a mask is applied to remove
data above the limb. Most of theMDI FDMG's contain a range of values
above the limb which are zero or contain noise. These generally appear
gray in the image making the sun look bigger. When activated, the
mask limb option uses header information from the FITS file (which has
to be correct of course) to force all pixel values outside the solar radius
to a -20000. This will normally make them all appear black in the image.

The "remove roll" check box controls whether a rotation of the image is
done to correct for a non-zero P angle (the keyword in the FITS header
is P_ANGLE). Usually this is already 0 and nothing is done. But there
are several times when SOHO was intentionally or unintentionally rolled.
The accurancy of the P angle may vary so don't be too surprised if
the image still isn't correct after a rotation.

Note that if a movie is using the MDI FDMG selection tool, these options
will also be applied when reading the files for the movie.

A suggested way to display MDI FDMG's is to leave all the options above
on and also set the image display to a fixed range between something like
-250 to 250. If the auto range is left on, the scaling will be different
for each image displayed which may be distracting.