Thanks. Sorry for the late reply. I image either with a ES127 refractor or a AT65 refractor. Lately, with my new mono 183, I've been doing 10 minute subs in Ha. Don't really see myself going longer than that. I haven't checked the cone error on the 127 yet because I have no way of shimming with the rings anyways. I checked the AT65mm yesterday and it was quite a bit off I'd say. It was enough to warrant shimming (for me at least) although I'll need to drill and tap some shimming set screw threads another day. I'm just skeptical about how well the ekos polar alignment module can do with a moderate amount of cone error or if cone error even affects how well it performs at all. I just don't know and I haven't found anyone bringing this issue up before but it seems like an obvious question to me.
What do you mean when you say you work backwards to compute the amount of rotation? When I first got my mount the polar scope was dead on, really dead on but I had to adjust it yesterday. I've noticed the DEC oscillation that you described in my previous nights. I too benefit from a larger DEC min mov maybe say 0.35-0.4. Haven't tried the Z-filter option. Not sure what that is but I'll look into it.
Lately my problem seems like it's DEC RMS being way lower than RA and my stars are a little oval. I had bad seeing the other night and both DEC and RA were way high but even and I had better looking stars at total RMS 1.4" than at good seeing (0.4-0.5") INTERESTING I thought. I use a OAG for the 65mm but I usually can't find stars with the 127mm so I use the 65mm to guide with. It usually work fine but obviously OAG would probably be preferred. I may give the 127mm another go with the OAG. I gave up rather quickly.