I´ve been looking for some guidance on this topic, but not finding too much, sorry if the question is a bit obvious for most of you.
I´ve been enjoying astrophotography for almost a year now, imaging mainly with a C9.15" and an 80mm apo, even using my Askar FMA 180 guide scope as an imaging one from time to time, always using a ZWO ASI 533MC as an imaging camera. Overall, no major problems with my guiding (I use APT and PH2D). I recently got a Rokinon 85mm and a 14mm to explore wider field of views.
Last night, and for the first time, I tried the 85mm lens with 533MC to shoot some wider fields of view, everything seems to work well, but I just couldn´t get a good guiding for this set up (I used a small 32mm William Optics guide scope). I usually get around 0.5 to 0.8 arc seconds when guiding (which I believe is not that bad), but yesterday I was AT ~1.3 to 1.6 arcseconds, no better than that. I shot 5 min subs (with L-Extreme filter) and got overall good shots, at least rounded stars...
I realized that the focal length of the guide scope is 120mm, which is quite larger than the 85mm lens that I´m using for imaging. Is there any way to guide an 85mm lens, or even a 14mm? Should I used a shorter FL guide scope (is there any that shorter??) Am I missing any basic piece in PHD2 configuration?
Many thanks in advance for the advices!