I don't think it is dithering. I tried to settle at 0.5 originally, and it wouldn't ever settle. SGP does not seem to actually cancel the dither, even though I enabled the "For x seconds" setting and set it to 10s. IT just sits there, waiting, and PHD is trying to settle at 0.5 and it just can't seem t do it, even though after only a few seconds it's back to tracking along the same as it was before dither. I upped that to 1.0, and it would eventually settle, but it took FOR-EVER. I tweaked that to 1.2, and it now settles, although it takes a lot longer than I used to be able to settle in the past (and I was settling at 0.65 previously.)
My individual focuses are wild. It's a sawtooth graph on a slope most of the time. Rarely get a V graph. I had V's for a short while when I first started, but I haven't been getting them lately. The graph will usually end on a down trend at the leftmost iteration, rather than on an uptrend, which is why I think the scope is cooling and focus is shifting faster than AF can keep up with. For a while I thought that maybe the focuser was slipping, but I checked the tension on it, and it seems to be fine. I started increasing my exposure times for AF, and that helped reduce the extremes, but I still get inconsistent results for each AF exposure, and the trend is always downward from right to left. I've manually forced reattempts a number of times, to see if I could get the AF routine to catch up to the cooling rate of the scope. But those second and third attempts are usually worse, with just wild results across the graph. Something is definitely wrong, though. My very first attempt at AF, the steps were around 4500. It settled around 4430. That eventually shifted to 4333. Then it was around 4200. It has been consistently shifting down, night after night, and I am now around 1700. I've double checked the tension on my Moonlite. It's pretty darn tight, tight enough that I'm worried it's too tight. I dunno...something very odd is happening...
I actually think my mount may be tracking poorly as well. I've had better than usual seeing lately. My stars usually scintillate so much that the brighter ones exhibit a full spectrum sparkling rainbow effect, however lately I can barely tell that they are twinkling at all. MeteoBlue has been saying that seeing is between 0.3" and 0.55" a lot lately. Their chart has been green across the board except for the jet stream, which has been yellow and orange (when it is usually blood red.) In the past when I've seen stars like this, my guiding (at least with the 600mm setup with the external guidescope) has dropped to 0.3" RMS. With the OAG on the RC, my guiding the last few nights has been 0.7-0.9" RMS. Most of these clear nights have been totally windless (also very rare for me). That pretty much just leaves the mount. I rebalanced it, tried the weight on a string to keep it east heavy, tried different amounts of weight, tried different amounts of shifting the weights down the CW shaft, tried different amounts of DEC imbalance. I've checked and tuned the mount's external bolts, nuts, screws and the bearing preload on both axes. Everything is solid and tight (but not too tight). The mount just doesn't seem to be tracking that well. Ironically, my 600mm setup with all the heavy ADM dovetails and rings, is actually heavier than the RC! And it tracks a lot better.
So, some of the softness is probably the tracking. Almost 1" RMS with an 0.482"/px image scale is going to soften things up. I honestly don't know if poorer tracking is going to affect SGP AF or not...but the AF has been terrible. I tried manually testing and setting my L vs. NB filter offsets a couple nights ago, and that improved things a little, at least earlier in the evening...then I went to bed. The later subs from about an hour after that were much softer. So the cooling of the scope was getting away from SGP. I then manually tested and tweaked the steps/deg, which SGP originally calculated at -42, then after trying again was updated to -48, and I finally ended up on -55. I think -55 is still a bit low, and I might try -60.
The interesting thing is, when I focus manually with SharpCap with a full video feed, I can really tell when the star is focused. I can start to see the airy disk, even with a moderate amount of scintillation. With SGP, even when it gives me a nearly perfect V graph and seems to think it's really nailed AF with it's HFD measurements, I can tell just by looking at those subs that they are not as well focused as I can get with SharpCap. I've tweaked the focus steps per AF iteration, down to as little a 5 steps (which is usually not enough to get a V graph), and it still cannot seem to give me the kind of tighter stars I was getting with manual focus in SharpCap. The other problem is when I switch from L to NB, the offsets are clearly wrong, and the stars end up even softer. I've fiddled and fiddled with the offsets, using the AF module as well as manually. I have not yet figured out the right offsets. I am beginning to wonder if the offsets may change over time as well. These are AstroDon filters, 3mm thick. I wonder if their thickness is enough that the difference between 22C and 9C could result in a change in the focus offset? There do seem to be times when the offsets work better than others...usually earlier in the evening they seem to be more closely matched, but by the end of my sequence things are pretty far off and the defocus is obvious.
Anyway. I've basically given up on the RC. I'm not an RC kind of guy. It would be interesting to get higher resolution images of planetaries and some smaller nebula, would be nice to do solar system imaging, but this thing has been nothing but a hassle. Collimation never holds, I have to tweak it every night and it's never quite perfect unless I fiddle for an hour. My mount's tracking (even guided with OAG) doesn't seem to be sufficient. It never stops cooling and the rate of cooldown seems to be fairly significant (between 90F days and 48F nights), so ironing out the AF details has been a pain. It's just...heh, I hate this thing. I'm not made for RCs.
If I get another high res scope, it'll be an EdgeHD. At least the collimation will be simpler. At this point, I'd welcome mirror flop. O_o And I think the Edge would better cater to my overall goals...the smaller secondary and higher F-ratio is better for higher contrast solar system imaging. It can be reduced to f/7.1, which would be great for other things, and it could be converted to hyperstar for fast wide field. I think, if I get back into high res stuff, an SCT and I will get along much better.
Hopefully someone else will be able to make much better use of this RC, the moonlite and the TSRCFlat2 than I have been able to.