Quote:All observations were done using the 10 inch Newtonian. My understanding is that you need at least 6inches of aperture to provide enough light gathering power to use an O-III filter. I haven’t tried it in my 4 inch Refractor for that reason.
Quote:My first use of the filter was on M57, the Ring Nebula in Lyra. This was done at a dark site South of Barstow in California. M57 was bright and easily viewed at a variety of magnifications without any filter. The addition of the O III filter did not improve the view and appeared, in fact, to detract somewhat since it darkened the field. M57 is a planetary nebula so this may account for the poorer performance.
David W. Knisely . . . . . . "If you aren't having fun in this hobby, you aren't doing it right." Hyde Memorial Observatory http://www.hydeobservatory.info Prairie Astronomy Club http://www.prairieastronomyclub.org
Quote:...all these three filters fit nicely with my TeleVue 2" eyepieces. On the other hand, the performance of the two Kson are not very satisfying.... .The bottom line is that the Kson can bring out more details in nebula like M57. In my light polluted site, M57 is difficult to notice for a novice, but adding a Kson make it stand out. I got the Kson filters dead cheap (about half the price of Irvin, so it is not too bad.
Quote:[But why put cheap, disappointing filters on your nice 2" TeleVue eyepieces? Why add a weak link? (Actually, to be further contrarian, IMO nebula filters do you a lot more good at a dark site....oh, they help a little under light-polluted skies, but I think it's best to save the faint stuff for the darkest skies anyway....)You will keep--and use--a good nebula filter for the rest of your observing life. Go ahead and get a good one....the price per use will go down rapidly, I promise!Cheers,Jim
Quote:I got the Kson filters dead cheap (about half the price of Irvin, so it is not too bad.