Re: Looking at data

[Stupendous Man <richmond@stupendous.cis.rit.edu>]

  Tom wrote earlier about a brief comparison he made between
a few Landolt stars and their Mark IV magnitudes.  I thought I'd
check for any obvious systematic difference, even though 4 objects
is a small sample.  Here's some more information about these
stars, for those who are interested.

  I used the V-band magnitudes of the stars to look them up.  I found
two matches for one of the V magnitudes, so I have 5 candidates.
Below are the names, positions, Landolt BVI, and TASS Tv and Ti magnitudes.


#  star        RA         Dec       B       V       I         Tv       Ti
SA114-223   340.13059   0.51802   11.19   10.62   .....     10.612   10.006
SA112-704   310.50833   0.31889   12.988  11.452  9.884     11.387   10.004
SA112-1242  310.59831   0.44508    9.502   9.088  8.587      9.067    8.641
SA106-834   219.86804  -0.24887    9.789   9.088  8.352      9.093    8.419
SA112-275   310.64761   0.12232   11.115   9.905  8.689      9.866    8.804


  Here they are again, with the (B-V) color of each star, and the
difference between Landolt and Mark IV measurements.

#  star       (B-V)     V-Tv       I-Ti
SA114-223      0.57     0.008      .....
SA112-704      1.536    0.065     -0.120 
SA112-1242     0.414    0.021     -0.054 
SA106-834      0.701   -0.005     -0.067
SA112-275      1.210    0.039     -0.115 

  The V-band differences _maybe_ show a hint of a trend
with color, but I don't believe it's significant.  The I-band
magnitudes _do_ suggest that a color term may be present
in the current Mark IV database I-band values.

  The sense of the I-band differences is the same as I found
in Tech Note 97.  

                             Michael Richmond