Eyepiece & filter quandary? Recommendations needed

I have a new scope, a 12.5" dob f/4.5. I also own a 5.1" spaceprobe. I have a couple of plossl's that came with it. The new dob I got here, with a 2" focuser, and I have a 1.25/2 adapter to be able to use the plossl's in either. I was interested in getting (1) a light pollution filter since I am in the suburbs, and based on what I read these should help to make some views a little more crisp of nebulas. (2) A nice new eyepiece for nebula/galaxies to use on ideally the dob.

Thus the quandary(sp?)...if I get a filter for the 1.25, I would like to use it on the dob as well, but that means the new eyepiece for the dob would need to be a 1.25 and not a 2 inch? I was assuming a 2 inch eyepiece, around 20mm-30mm.

Would I be losing much by sticking with 1.25 eyepieces for now? If not, could someone point me in he right direction on the size? Been reading up on these, but since I am gonna spend some money, I don't want to make a mistake...was probably targeting around $100 for the EP (maybe the GSO 2" SuperView Eyepiece - 30mm, since it seems to have had some good discussion), and was going to get the orion Ultrablock filter. Thanks for any help!

Matt

A compound problem, but I like your preliminary solutions. First, you want a 2" eyepiece to get the widest usable field in your new Dob. The 30mm GSO seems a reasonable choice, because it results in a 6.7 mm exit pupil, and, presumedly, has a 70°-80° apparent FOV.

My only caveat there is how the edge performance will hold up with a f/4.5 focal ratio. I have a 12.5" Dob with a f/4.8 ratio, and quickly decided a Paracorr was necessary to deal with the coma I saw in my 2" lowest power eyepiece. But your mileage may vary, and I cannot argue with your choice given your budget.

Regarding the light pollution filter, I think you are on the right track with the Orion Ultrablock, a "best buy" in narrow band filters (and you are wise to avoid the relatively worthless broad-band filters). I would get the 2" version, which is only marginally more expensive than the 1.25" one. Eventually, you will have both sizes, and probably O-III filters as well in both sizes. But for the grand large emission nebulae (e.g. the Orion and Lagoon nebulae) I think the wider field version should be your first purchase. After that, I would get a 1.25" O-III for the planetary nebulae.

Hope that helps.

Hugh Bartlett

Under the review section eyepiece/other check out the one on GSO eyepieces. I have used the SV 30mm at f/6.2 and it worked very well for the price I paid (preowned from this site $35). I also tried the 42mm and was happy with it but eventually replaced it with a 40mm Paragon. At f/4.5 expect some edge deterioration. How much this bothers you depends on your expectations. Naglers and Panoptics cost what they do because they are well corrected for use with fast telescopes.