I've been able to validate that both my imaging camera and my OAG camera can achieve simultaneous focus. I did this during daylight hours. My guide camera is a QHY5III462C I bought for planetary imaging and thought it could also double as a guide camera. However, to get the camera positioned in the OAG low enough to achieve focus I have to unscrew the sensor cover and can not use the IR filter. The resulting images during daylight hours look FUNKY. I've ordered a monochrome camera specifically for guiding. It will hopefully arrive soon.
Last night I decided to only guide and ignore imaging. This was hard because it was completely clear!!!!
I got my rig assembled and balanced. I balanced with a slight east bias. Then I polar aligned. After achieving focus with my imaging telescope (using a Bahtinov mask), I slewed to the rosette nebula and then plate solved. I thought this was as good a place as any to test guiding.
I started up PHD2, and went through a new profile wizard. After going through the profile wizard, I started looping in PHD2 and then worked on getting the OAG camera in focus. Using the helical focuser on the OAG I got the guide camera as focused as I was able. Again, the stars were not round; they were "roundish". These are the best shapes I've been able to achieve after doing a LOT of trial and error work on adjusting back space (in 1/2mm increments).
I set my camera exposure to 3 seconds and let it guide for almost an hour with all the default settings from the profile wizard. The RA algorithm was Hysteresis and it only used single star guiding. After 53 minutes my total RMS was 1.02", but the overall variance in guiding looked pretty good. There were no "large excursions" like I've seen in the past. The RA RMS was 0.82" and the DEC RMS was 0.65". The RA periodicity was clearly evident in the RA plot.
I changed to multi-star guiding and changed the RA algorithm to predictive PE. I then ran a GA for 10 minutes. I implemented all of the GA recommendations. It also suggested I improve focus on my guide camera, but the focus is as good as I can get it.
I guided for an additional 40 minutes. This session produced a total RMS of 0.76". The RA RMS was 0.61" and the DEC RMS was 0.45".
According to the GA results: RA-HPF: 0.18"; DEC-HPF: 0.07"; Total HPF: 0.21". This pretty typical for my seeing.
My RA RMS was 1.4x greater than DEC RMS. The GA seeing measurements show RA HPF at 2.6x greater than DEC HPF. I'm interpreting this to mean my RA RMS is not out of line with my DEC RMS given the seeing conditions. Is this a correct conclusion?
Overall, this is the best guiding I've achieved. Ideally, I'd get this down to ~0.5" of total RMS. My first step will be to install the new monochrome guide camera and see what results. I may also spend some time adjusting the tilt screws on my camera to see if I can improve the edge star shapes a little. Then, I'll start changing some algorithm parameters.
For thise who have gone down this path, where do you start "tweaking" in the algorithm parameters? Should I start on the RA algorithm or the DEC algorithm or both?
This is tedious work, but if I'm going to drop my image scale from ~2.01"/pixel to ~0.8"/pixel I'm going to need to do the work.