Ok … I’m imaging small targets - mainly galaxies and planetary nebulae - that are rarely imaged, at 3000mm f/12. It’s not uncommon with galaxies to line u on the target only to find there isn’t a suitable guide star for the DUO, and there are three approaches to find one:
- panning around a little, up/down/left/right, or
- stay centred on the target and rotate, or
- switch to the piggyback guide scope instead.
I recently bought an ASI676MM to use as the guide camera as this has pixels half the size of those in the ASI120 Mini, and on the first coupe of attempts it looks like it works fine, field is big enough to find guide stars always at f/7, the guidecanera image scale is around 0.8 arcsec/pixel while the main camera is 0.25.
So no more need for rotating.