Four nights ago mid-session, the camera I had been using for a guiding, an ASI183MM, died (sort of). I suspect this is an issue with ZWO drivers and PHD2 (cords and Pegasus Astro hub all working fine). This has been happening recently, but I didn't feel like chasing the issue down since I had another camera I could use. I replaced the ASI183MM with a Player One Apollo-M (IMX174) I use for solar imaging, created a new profile in PHD2 and recalibrated.
I noticed immediately that my guide graph looked a lot "better." The jumps in error I'd see were much more contained and my total RMS for the session was about 30% lower than it had been 30 minutes prior. Over the past several nights, this has held up. Whereas before it was standard to see average RMS over a session between 0.70" to 0.80", I have been between 0.40" and 0.60". Seeing hasn't been particularly better (and noticeably worse one night) and I've been imaging the same two objects as I had been before switching out cameras and imaging them at the same times each night. The stars in the PHD2 fov are crisper, cleaner and rounder with the Player One and guide scope combination.
Could the significantly larger pixels in the IMX174-based camera lead to a lower report RMS? Note that I am not arguing that my guiding is "better." I just know that the jumps are I see are much smaller in both the graphs and in the PHD2 logs I've viewed.
Background:
I'm somewhat luxuriously using a 90mm triplet (600mm fl) as a my guide scope for the time being. Considering I'm guiding a 115mm triplet reduced to 523mm fl, it is probably overkill, but I have the mount capacity for it (Losmandy G11). Everything is attached using ADM and Losmandy clamps and dovetails. The cameras weigh about the same (quite light) and my focuser on the guide scope is not racked out at all.
The reason I'm even bothering to look this gift horse in the mouth is because I will be upping my game over the next several weeks with a mount axis upgrade (Losmandy G11T Titan axis upgrade) and attempting to image at 1960mm focal length. Any info I can get on what could cause such a decrease in RMS values (whether real or just as reported by PHD2) would be helpful.
Regards,
George