***** File BROWSE.TXT                                                         
                                                                              
     Effective use of the large images contained in this CD-ROM requires that 
the user of the disc be able to "browse through the data" quickly to find     
those images and intervals which are of high scientific interest.  Because of 
the long decompression and transfer times of the full-resolution images with  
current image display hardware, the goal of efficient browsing of the data can
                                                                              
be met only if the images are placed on the discs at least a second time, in  
either subsampled or filtered form, and uncompressed.                         
                                                                              
                                                                              
     This was done for the compressed images on this disc and the results are 
located in the BROWSE directory of this CD-ROM.  A set of "browse images" has 
been generated for which the images are uncompressed, subsampled and are no   
larger than 256 pixels in either dimension.  In addition, the digital data    
have been scaled into a numerical range of 0 to 255 (one byte per pixel; the  
precision for most of the original images is 10 bits, requiring two bytes per 
pixel).  The BROWSE directory of this CD-ROM contains datafiles, FITS headers,
                                                                              
and PDS labels for the compressed images on this CD-ROM.                      
                                                                              
     The browse data were obtained by taking the "n"th row and column for the 
original image starting at row "n/2" and column "n/2".  The value for "n" was 
determined from the larger of the two axes such that the quantity (original   
length / n) was less than or equal to 256.  For the images which were         
digitized at GSFC, the original densitometer values ranged between 0 and 1023.
The density values in the images were divided by 4 in order to convert the    
density to a single byte.  For those images digitized elsewhere, the density  
scaling factor was chosen so that the density in the browse image was less    
than or equal to 255.                                                         
                                                                              
     The FITS header records for the browse images have had their astrometric 
information adjusted to reflect the change both in pixel spacing and image    
origin.  Thus, should the user wish, (crude) astrometry can be performed with 
the browse images.  In addition, HISTORY keywords have been inserted to       
document the linear scale and density scale changes.  The creation of the     
browse images was accomplished using the program MIDGET, which can be found as
MIDGET.FOR in the FORTRAN subdirectory of the SOFTWARE directory for this     
CD-ROM.