It's widely accepted wisdom to use OAG when you go with long focal, especially with SCT due to mirror flops.
Despite of practically everyone's despise on my 3D printed finder converted guider, it works pretty well for my setup, I think. But there is always something to make it better, right? So, I'm doing another push on OAG, which I tried several times but has been miserably failing.
This time, it went kind of okay. Find focus(ish - how do you confirm it's really focused? Bhatinov mask is impossible to use. Any tips?) and PHD2 found handful stars for multi-star guiding. 300s sub shows good round stars. Guiding numbers are worse than guider setup but image it takes matters not PHD2 number. So I kept going.
I can't find it apparently better than guider but at least it was good start.
Problem happened when I tried to setup for overnight automation. Loaded auto sequencer in NINA and started. Plate solved, centered, focused, all good then failed to start guiding. Why? There is no stars detected. The target was on deserted area. Increased PHD2 time to 5sec. Still no stars. Increased to 15sec, now barely faint stars showed up and I could start guiding. Typically this could be resolved by rotating OAG to find guiding stars but I can't do that for overnight automation.
Prescription I can expect would be to use bigger prism OAG (currently ZWO 8mm one) with bigger sensor guide cam like 174mm (currently 290mm). And better focus might reveal some fainter stars, I guess. Would this really lead to 'always' finding guide stars?
Probably this situation was aggravated by dualband NB filter for OSC but I can't image without it under B6+ sky.
Can you share your wisdom on using OAG for long focal AP? Currently it's at F=1780 (C11/0.63)