Quote:
Originally Posted by skysurfer
Well, I have a small 1.25" Lumicon UHC filter, but it vignettes in my 24mm ep. So I want to buy another one of 2". I take an OIII or H beta also as an alternative. Even higher contrast and a H-beta even should show the Horsehead and California nebula. After reading this CN article discouraged me from H beta and I prefer a UHC again. I'll use it with:
40cm Dobson at home, moderately light polluted and 10cm Genesis or 15x70 binos on a dark location.
What would you recommend? |
If your 24mm eyepiece is the 24mm Panoptic then it has a 27mm field stop diameter and this is almost maximum for a 31.7mm (1.25") barrel eyepiece.
You will therefore find that just about any filter on the market will vignette slightly with this eyepiece. However your UHC may also have a thicker cell wall in which case it will cause significant vignetting. I have only seen this once with Lumicon on a 2" Comet (Swan band) filter that had a much thicker cell wall than the other 2" narrowband filters. It could be an older filter from an earlier production run.
I concur with others recommending Lumicon as they have been making filters for a very long time and do produce a very fine product. Of the Lumicon filters, I find my first choice on my larger aperture telescope (25cm) is the Lumicon O-III and whilst this filter also works well with my smaller refractor (10cm), I prefer a more gentle filter on it and then choose the Lumicon Deep Sky filter which basically just darkens the background a little and gives a more natural view.
However, there is a very good alternative that you may like particularly on your Genesis and that is the Tele Vue Bandmate O-III. Some will argue that this is not a true O-III filter since it is a little wider in bandpass but it has been designed to give a very natural view. Also this filter does not show red/blue fringing on bright stars as some other filters do. The trade off though is a more greenish but sharper view. See
http://www.televue.com/engine/TV3b_p...t#.UytXYKiSy5I
I really enjoy views through the Tele Vue Bandmate O-III and a variety of telescopes from small refractors to larger reflectors. You would not be disappointed with Lumicon or Tele Vue.
Another option for your 40cm telescope is the Thousand Oaks O-III. On a 25cm telescope this filter gives me the best contrast with jet black background and stunning nebula (Eta carina is sensational!). This filter would be ideal on 40cm with more light to play with. I find though that this filter is a bit too severe on smaller telescopes (for my liking at least). (I'm not sure if a tighter bandpasss or less transmission gives the jet black).
Exit pupil is important and the more the better I find and this is where larger aperture helps but the filters do work well in smaller 'scopes, just some better than others.
