PhotoGav

An interesting question indeed! I have normally managed to get my PA to just under 1 arcminute accuracy as reported in Alignmaster and have had great guiding results. I set up on Saturday night and ran Alignmaster quite a few times, but just couldn't get a, what I thought was, good PA. The accuracy was around 8 or 9 arcminutes I think. I finally decided to stop the futile fiddling and started imaging. Guiding was spot on, stars are round and all was fine for two nights in a row (wow I hear you say, two consecutive nights imaging... that's a rarity!). So, my conclusion is that, when guiding, you can get away with a pretty large inaccuracy. When unguided, it's a whole different matter though... The closer to perfection the longer the subs you will manage. My unguided test shots over the last two nights were pretty shocking! I did a 60s sub of M27 and the trails are horrendous!