nebula filters

I want to get a filter to bring out the contrast of the various nebula. I have a 6" sct and dont want to block too much light, as with only 6" of light gathering strength, light is in short enough supply! I was thinking about an Oxygen 3 (O-III) filter. would anyone recomend/denounce this filter and if so, what would you recommend?


Thanks Guys

Fintan,

I wouldn't recommend an OIII as general purpose nebula filter for visual use. That will pass a very specific wavelenght that not all nebula's emit/reflect.

Much better would be a UHC filter or a general broadband light pollution filter. I've used a Lumicon UHC a while back and it is really excellent, albeit expensive.

I agree with Dave. You really need at least 8" of aperture to use an O111 filter as it blocks out too much light. Have a look at the telescope service web site on filters-they have some good advice on filter selection. The astronomic UHC filters are supposed to be very good also. I have the Baader UHC and O111 which are quite good and not expensive.

Hi

The OIII filter may darken the image too much. You would be better off with a UHC filter. There is also a UHC -E which may be more suitable for a smaller aperture scope.

I have to echo John's comments. I have a Baader 2" UHC filter and find it useful, in my 80mm refractor I was just able to make out the Veil Nebula and in the 127mm it gives good views of the M27 and M57.

As a good all round filter the UHC is ideal.

Do what I did and go to an observing session where someone else has these filters and judge for yourself.
To be honest, you'll be hard pressed with an O3 filter and 6 inches of aperture, not enough light there probably. The UHC is the one for you.