eliot

Hmmm.  I had suspected as much.  Thanks for the recommendations.

I'm normally an imager so not greatly experienced with visual astronomy.  However recently whist imaging rig is running I have been having fun learning how to star hop again with an old 12" dob a friend gave me when he upgraded scopes.  The mirror is in desperate need of recoating, but with a Baader Zoom and 2" Meade 34mm eyepieces the images are nice and sharp.

I have been trying to find the Veil Nebula.  Unfiltered from my (darkish) garden I have struggled.  I bought second hand 2" UHC and OIII filters from flea bay to help me find it.  They appear to be the kind that OVL sell.  The OIII filter wasa great help but the nowhere near as good as I had read it would be.

One thing I had noticed was the how soft the image looks with both filters.  With some delicate focusing I can get the image to be OK, but nowhere near as good as unfiltered.  However If I take the filter from the back eyepiece and hold it up again the front the image appears much sharper.

The scope isn't amazing fast (f/5), but the barrel of the eyepiece is quite long.  Could this be caused by a distortion in the light cone caused by the filter glass?  I would have thought restricting the light bandwidth would have made the stars tighter if less luminous?