O111 Comparisions ?

[astrobase1]

Hi all , I am considering buying a 2" O111 filter for my 8" f6 dobsonian . Has anybody done a comparison of various manufacturers on a similar scope? I have seen prices from £46 (castell) to £196 (astronomik) . Are some noticeably better or worse .

[John]

I've owned O-III filters by Baader, Celestron and now a 2" Astronomik. The Baader and Celestron ones were both identical (the Celestron was clearly a re-branded Baader) and I found their bandwidth pass width too narrow for my tastes, even with an 8" F/6 dobsonian that I owned at the time. The Astonomik is expensive compared to others on the market (although mine was a used purchase) but I find it superbly effective - the band pass width is wider so it's effective even with my 4" refractor and the quality of optical glass used seems excellent - star images are more pointpoint than with other filters I've used.

That said, it's well worth seeking feedback on the Skywatcher, Castell and TS Services O-III filters as their costs are very reasonable and their band pass width seems less "harsh" than the Baader from the graphs I've seen.

Another very respected brand is Lumicon although their prices tend to be on the high side as well.

TBH, given the amount of times I use it, I would hesitate to pay the new price for an Astronomik, despite it's qualities. I was just lucky to stumble across a used one at a good price

[A McEwan]

I had a Thousand Oaks 1.25" OIII (which I've lost!) and bought a 2" model from an unbranded US seller on ebay, who made them himself along with a whole range of other filters. The 2" performs excellently - about the same as the Thousand Oaks one did. The 2" format is great for wider-field 2" eyepieces too.

[Andrew*]

I have a Skywatcher one and have to say I had my doubts about it. They all vanished when I first tried it - it is an excellent filter, especially at its current price tag of £69 for the 2".

Andrew

[astrobase1]

Hi All

Thanks for the response , I looked at the 365 website for the Castell , very interesting as they showed a bandwidth comparison chart which clearly shows the Baader has a very narrow cut off . I have the Baader UHC-S so I think i,ll stick with that until funds allow a Lumicon UHC (mid way cut off between the Baader UHC and Baader O111 .

Many Thanks