The SXT synoptic maps are constructed from strips extracted from full disk
desaturated SXT images made using the thin aluminum filter. Each map
depicts a single Carrington rotation. There are three sets of maps,
corresponding to strips centered on the central meridian of the solar disk,
45 E longitude, and 45 W longitude. The widths of the strips are determined
by the time differences between images. For a given map, as many full disk
images are used as are available provided the time difference between
contiguous images exceeds 1.5 hours. Due to occasional gaps in the coverage
of full disk imagery, some of the synoptic maps show corresponding gaps.
The maps constructed from strips centered at the 
degree longitudes are
distorted at high latitudes because vertical strips are extracted which do
not follow the longitude line. The images from which the strips are
extracted have been registered to remove the effects of spacecraft pointing
changes. Each strip is shifted along the vertical axis so that heliographic
latitude 0 is always centered in the assembled map. However, projection
effects in the vertical axis have not been removed. This means that the
latitude scale is not linear but reflects the cosine projection effect of a
spherical structure (the corona) projected on to a flat image.
The following are some examples of how to display the synoptic images which
are in the Yohkoh database. The first example just displays a single
synoptic map for the central meridian for carrington rotation number 1860.
The second example displays three SXT synoptic maps, central, +45 and 
.
The third example has a single synoptic image which is the Kitt Peak
magnetogram for carrington rotation number carrington_rot_num.
The fourth example shows SXT central meridian and the Kitt Peak magnetogram
and He 10830 synoptic maps.
IDL> disp_synop, 1860
IDL> disp_synop, 1860, /allsxt
IDL> disp_synop, carrington_rot_num, /kpmag
IDL> disp_synop, carrington_rot_num, /gbo
An example of how to read one of the SXT central meridian synoptic map
images is shown below, along with an example of how to read a Kitt Peak
magnetogram synoptic map for carrington rotation number 1862.
IDL> rd_xda, '$DIR_GEN_SYNOPTIC/ssc_cr1862a.01', -1, index, data
IDL> img = rfits('$DIR_GEN_SYNOPTIC/gkm_cr1862a.01', header=header)