[Solanum]

Firstly, my GSO 10" Dob has a 2" focuser, but my eyepieces are 1.25" (with adapter). What are the essential differences between using 2 or 1.25" eyepieces? If I have a 9mm 2" and a 9mm 1.25" eyepiece are they the same magnification? If so, is the exit pupil size different, making the 2" easier on the eye? Is the field of view different? Please feel free to point me to a thorough online article on this if it's easier.

Secondly, I want to get a couple of filters (polarising for moon viewing), can 2" filters be used with 2-1.25 adaptor or do I have to get 1.25" for the eyepieces I have (although I have a 2" barlow).

Thirdly, can anyone recommend an online store for reasonably cheap filters?