IHW_PHOT
--------

 o Add to the addenda tables information on the zero-point reference for
   the magnitude scales.  See Gehrz et al. (2005), AJ 130, p 2383-2391.
   Cite this and Gehrz&Ney (1992).

 o addenda3.tab: Column 8 should say "black body temperature at the 
   comet's heliocentric distance";
   Column 10: "superheat of the continuum emission" add 
   "= T_color/T_blackbody"

 o Identify addenda as the data set from Gehrz and Ney (1992), Icarus 100,
   p 192.  (Add citation and consider proof-reading) M. Hanner will send 
   descriptive paragraph for dataset.cat.

 o Add citation for Gehrz & Ney (1992) to addenda3.lbl for detailed column
   descriptions.

 o target.cat file for Halley has too many "significant" digits and no units.