Hi Malcolm, unlike you I am still a newbie with the S50 but, like you, I plan to use it for photometry. Some of my initial research may prove useful to you.
First, the seestar_alp program is a useful extension of the iOS / Android control app. Put the S50 in station mode and control it with a real computer with a real screen, real keyboard, and real mouse, doing so from a nicely lit and warm room indoors. The program supports RA&Dec input (in J2000 and Jnow) which can be taken from a variety of sources such as Simbad as well as being typed or pasted in. It is wrotten in Python & Javascript and allegedly runs under Linux (most hosts, including RaspberryPi), Windows and MacOS. Find it at https://github.com/smart-underworld/seestar_alp
Second, AAVSO have published a set of transformation coefficients which allegedly convert native RGB measurements into (an approximation to) standard BVR photometry bands. These can be found at https://www.aavso.org/bvr-transformation-coefficients-seestar-s50
Finally, here is an image of SS Cygni taken when the VS was in outburst. I have not measure the FITS files yet.
HTH,
Paul
