[SamD (Sam)]

Been using Skywatcher EQ5/6 mounts for over a year now, and been guiding happily, getting RMS in PhD (RA+Dec combined) of about 0.5 to 1.0''. Images have mostly round stars when imaging with an ED80 at about 2''/px. I'm now chasing more resolution with a longer focal length RC8 at about 0.9''/px, and considering if any of the mount overhaul/belt mods around might help.

Does anyone have any experience in how easy it is to get tracking RMS on these SW mounts down to say less than 0.5'' in RA with typical mods, or in fact, any experience to what extent mount mods actually help in getting tighter stars and better resolution (under typical seeing) ?

In theory, a RMS tracking error of 1.0'' on a normal distribution equates to a FWHM of 2.355''. Even with this largish tracking error, it seems that a typical 3'' seeing disk FWHM will still be the dominant factor in overall star FWHM, so why bother ? I suppose with very good seeing of say 2.0'', it would make sense to try and lower the tracking RMS on the mount. So, theory seems to say it's only worth mount mods to benefit from occasionally good seeing. Does this make sense ?