Thanks everyone
At this stage I don't have plans for any 2" EPs. I just thought that looking through a 2" barlow with a 1.25" EP might minimise the degradation that a barlow normally gives - i.e. I'd be viewing through the centre area of the barlow elements (beginner's logic
).
At this stage I don't even know what the 4 EPs are that come with the GSO. I know the GSO web site says that a 9mm Plossl (1.25"), a SP32mm Kellner (2"), and a moonfilter are standard with the 10" dob. Funny that Andrews make no mention of the Kellner and the moon filter.
Maybe I'm better off waiting til I start using the scope with the EPs they provide, then decide what I want next. I think I was taken in by what seemed to be a good price for ED elements
.