We are excited to announce the launch of our new forums! You can access it forums.aavso.org. For questions, please see our blog post. The forums at aavso.org/forum have become read-only.
Announcement: New Applications
The existing WebObs will soon be replaced by WebObs 2.0! Please use this application to submit future observations: Submit Photometric Observations
Some conversion references:
http://www.aerith.net/astro/color_conversion.html
http://arxiv.org/pdf/astro-ph/0609121v1.pdf
I have not checked, but I think that should answer your needs.
What we use in Seqplot comes from Jester, et al. (2005)
V-Rc = 1.09 * (r-i) + 0.22 +/- 0.03
Rc-Ic = 1.00*(r-i) + 0.21 _/- 0.01
for stars with (Rc-Ic) < 1.15
We expect to derive our own relationships later in the project.
Arne