Alistair,
Some food for thought.. if you want to bump up the mag on those targets, and many from what I understand take higher mag well, that 2" filter wont carry across your 1 1/4". Higher mag eyepieces don't come in 2". I didn't know that when I first bought my scope and spent lots of $$ on a 2" barlow.
. Just something to think about.
I'm not a big expert when it comes to pn's but I know with the Ring neb (M57) takes a 10mm very nicely on my 10" dob (I see you have an 8" ?), the Ghost of Jupiter takes a 15mm nicely, and the Orion Neb looks amazing in a 15mm and a 10mm. Just a couple of examples.
My advice (whether taken is completely up to you of course), go the 1/4" filter for now, get the 20mm ep in a 1 1/4" and then later if you still find you want it, go for the 2".
As for your request, your wish is my command, so here you go.
http://www.eaas.co.uk/cms/index.php?...-zone&Itemid=8
http://www.lumicon.com/astronomy-acc...d=1&cn=Filters
And my favourite one:
http://www.raycash.org/filters.htm
Knock yourself out!
