***** File CALINFO.TXT                                                        
                                                                              
     This directory contains compressed digital calibration data associated   
with some of the Halley images obtained by the Large-Scale Phenomena Network. 
                                                                              
     Text tables linking calibration and Halley files are given in the file   
CALIB.TXT in the DOCUMENT subdirectory, and a delimited index of the same     
information is in the file CALIB.IDX in the INDEX subdirectory.  [N.B.:  most,
but not all calibration data are contained in separate files; some are        
deposited on the Halley images themselves.  Refer to the last section of      
CALIB.TXT.]                                                                   
                                                                              
     The type of calibration varies: there are sensitometer spots, step       
wedges, and standard stars, depending on what was provided by the original    
observers. FITS headers provide all of the known information about the        
calibration data sets, although in some cases no relative intensities for     
(e.g.) step wedges were provided by the observers.  A previous pixel          
compression technique was used on the calibration data in this directory and  
on the full-resolution Halley images in directory Cyymmmdd; refer to the file 
COMPRESS.TXT in the DOCUMENT subdirectory for specific details on compression.
A full description of the calibration data themselves is given in CALIB.TXT,  
also in the DOCUMENT subdirectory.                                            
                                                                              
     The extensions for files of calibration data follow the IHW filename     
conventions (.IMQ = compressed image, .HDR = header, .LBL = label).  To       
reconstruct the original FITS byte stream, the .HDR and the .IMQ files for the
appropriate observation must be concatenated.  The original FITS headers have 
been modified using the FITS extensions to take account of the fact that the  
data have been compressed.                                                    
                                                                              
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NOTE:                                                                         
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The "directory Cyymmmdd" mentioned above refers to the single data directory  
included on each of the original 18 CDROMs comprising this data set.  The     
data directory name began with the letter 'C', followed by two digits         
indicating the year, the three-letter month abbreviation, and the two-digit   
day of the first observation in the directory.  All observation files were    
located in the same directory on those disks.                                 
                                                                              
All observation, browse and calibration files have been sorted into a         
year/month/day directory hierarchy in this presentation of the data set.      
                                                                              
- A.C.Raugh 2011-05-16