You can do a lot with 5 minutes at 300mm - that's great!
Thanks! No, it's faster than that. Mine's a 102/621mm.
I started out with a 50/200mm guide scope, and on Jerry's advice went to a 60/280mm. That helped considerably.
My guide camera, well...
When I picked it, I had no idea and just wanted 'something to guide with', so I went for versatility and ended up with an Altair GPCAM2 IMX224 Color, with 3.75um pixels. Just the thing for shooting Jupiter with, but not what I'd pick for a guide camera, if I had to do it all over again. One of these I'll probably switch it out for something IMX290-based and mono, w/2.9um pixels - and that should give me another bump.
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras: Nikon D5300, Altair GPCAM2-IMX224C
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer: Thinkpad x230, Win7Pro/64