Proper Motion of M38

I was amusing myself by taking VRI photometry of M38 and making a CMD
to prove to myself that the main sequence exists. It appears that it
does. I was then going to exclude field stars that were not part of the
cluster based on proper motions. I used the proper motions from UCAC2.
Using the 520 stars in my (fairly large) FOV I get an average proper
motion in RA pmRA=-2.4 mas/yr and and in declination pmDE=-6.7 mas/yr.
Yet a reference I found (de Oliveira et al A&A 390, 103-108 (2002))
states pmRA=3.6 mas/yr and pmDE=1.9 mas/yr.

First there is the issue with the sign and second the issue of the
difference in magnitude, especially in declination. My average is
contaminated with all the field stars, but the cluster dominates the
frame and most of the stars are from the cluster. The field stars may
also sort of cancel each other out.

I have a plot he

http://www.lolife.com/astronomy/HR.jpg

The magnitude scale is internally consistent but probably +/- 0.05 or
more in relation to Landolt standards.
Cheers,
Michael Koppelman
http://www.lolife.com/astronomy/