Eric
Hi, I'm glad to hear that someone else is experiencing the same problems as me.
On my first setup I use a Sky-Watcher Quattro 200P (200/800) with an ASI2600MC Air, which also has the built-in ASI220MM guide sensor, just like the ASI2600 Duo. My filters are an Optolong L-Ultimate 3nm and an Altair Ha/OIII DualBand 4nm, and I image from a Bortle 5 site with an SQM of around 19.4.
When I'm doing broadband imaging without any filter, I have no guiding issues at all. However, with narrowband filters, the only way I can achieve stable guiding without constantly losing guide stars is to use BIN2, gain 600 (maximum), and guide exposures of at least 3 seconds.
I'd also like to point out that this behavior only started about five months ago. My setup has been exactly the same for the last two years, so I suspect that something changed with one of the recent software updates.
The incorrect guide image contrast issue (where the guide window is either completely gray or completely black) has been present for more than a year. I've seen it with the ASI2600 Duo, the ASI2600 Air, and even with a standalone ASI220 Mini, so it doesn't seem to be specific to one camera.
I've reported the guide contrast problem to ZWO several times. They acknowledged it and said they would fix it, but unfortunately it still hasn't been resolved.
Regarding the difficulty guiding through narrowband filters, ZWO told me that this is normal and is related to the characteristics of the equipment being used, not to the software itself.
