The dobsonian has 1200mm focal length, divided by a 6mm eyepiece = 200x magnification;
200x magnification will work most of the time (depending on the atmospheric seeing conditions more isn't always usable anyway).
The 15mm can be a great mid-range eyepiece for deep-sky (larger exit pupil, 80x magnification)
.
es30mm70° -> Odd, I looked at three stores, sold out, only the smaller one and the 82° are still on sale.
Other options are the
or the q70 from Amazon
...for example.
This one is also on sale and not bad either!
The cheap 30mm80° has a few controversial reviews with a 8" dobonian (F/6). For <$100 it's alright. The inner field's sharpness is comparable to the ~30mm70° eyepieces with the added bonus of a bit more field of view. Both work and are a good upgrade to the 25mm 52° kit eyepiece.