[guide-user] question ('bout magnitudes again)
Jan van Gijsen Dec 27, 1999
Hi Bill,
Followed your advise using (S)A2.0 data.
I downloaded two minor A2.0 catalogs from internet (some 40 Mb) and got
the SA2.0 catalog from USNO by post (within a week !), installed them
on my harddisk using the a2_path option in the "guide7.dat" file. Works
really great.
What i did too is some downloading form Lowell's observatory from the
USNO
A2.0 catalog. After renaming the out######.bin to A10.dat this also
works OK.
But having a A10.dat file in my guide7 directory seems to disable the
path option mentioned above.
This is not so bad: i can rename A10.dat to its original.
What I saw was that using a A10.dat (or setting a low, say 12, magitude
limit in the A2_path) will cause some stars to appear twice, and
showing two
values for it's magnitude. What really struck me were the differences
in value.
Did some checking: on a map area near DENEB (level 11: 8 min) there
were 18 stars with double values, the one on the top always brighter.
differences were between 0.2 and 2.0 magn. averaging 1.2 magns.
Is there an explanation for this difference, or is the routine
calculating the
visual magnutide from the red and blue values simply not acurate
enough??
Whatever: I'm still curious if it's possibly to omit magnitude values
for
brigther stars, as mentioned in my previous mail. This way i could
ignore the problem.
Clear skies
Jan.