[Aavso-photometry] Questions on Henden sequences

[Michel Bonnardeau]

I try to use the Henden sequences and I have the following questions:

Most of the files have columns for V, B-V, U-B, V-R, R-I but sometimes 
there is a 6th column for apparently another magnitude differential. 
Is it I-J or something else?
Example: doher.dat.

The errors on the magnitudes may be negative. What is the meaning?
Example: 3c279.dat.

I would be grateful for any help.

Best regards, 

Michel
http://mbond.free.fr