Hi Glen,
Having setting circles on my 10" DOB, I know how accurate these can be.
But their accuracy depends on several factors.
You already know about levelling the base, and setting it up accurately allowing for magnetic declination.
So that narrows it down. . .
The question was asked what are you using to obtain your target Alt Az co-ords?
As I am sure you know, Alt Az is constantly changing, and is different depending on what your Longitude and Latitude of observing location. So if you are using a computer program (like Stellarium) you need to have it properly set up for your co-rds and observing time.
When I set up, I find and easy object, say Alpha Crux, and fine tune so the setting circle readings exactly match the Program Co-ords for that TIME. Once you do that, you should be happy to find faint fuzzies all night.
Hope this helps
Allan
