OIII filter that's not too tight on bandwidth

[crazyjedi]

Can anyone recommend an OIII filter that isn't too tight on bandwidth??

As you can see from my sig I only have a 150 newt hence I don't have alot of light grasp to loose through the filter. OIII are uisually recommended for 8 inch newts or larger but I've heard that people are happy to use them with 6 inch scopes. There is a certain amount of variability from one filter to another with regard to band pass hence I'm keen to find a filter that is usable with my scope

Cheers:icon_scratch:

[John]

The Tele Vue Bandmate O-III and the Astronomik O-III have a slightly wider band pass width than most O-III's. I have the latter in the 2" size and it's very effective even with my 4" refractor.

The "rub" is that they are not budget filters I'm afraid.

[DOBBY]

this link might help....

Castell OIII Deepsky Filter for 2-Inch Eyepieces [Castell-Doiii2] - 46.56 : 365Astronomy: Discovery for every day!

UHC is normally better in under 10 inch 'scopes

[John]

The Castell O-III looks to have a wider band pass width than the Astronomik O-III if the table in that link is accurate. The Astronomik is certainly excellent with a 4" aperture (I've seen 3 segments of the Veil nebula using mine with my 4" refractor) so I guess the Castell might work well with smaller aperture scopes too.

[crazyjedi]

I Have a Baarder UHC-S which is good. Just wondered what i could get hold of that offered more detail that was usable with my scope.

[John]

The UHC-S is quite a gentle filter and was designed with smaller aperture scopes in mind. An O-III filter will have more impact on some objects as will a "standard" UHC such as the Orion Ultrablock.

The above don't work miracles though and dark skies, little or no light pollution and no moonlight around are even more effective in many ways. There are a handful of objects such as the Veil and Owl nebulae that are very difficult to see at all without a UHC or O-III filter. These filters don't help with galaxies and clusters though.

The UHC-S filter is quite effective though and I had my 1st views of the Veil nebula with a 100mm scope using one.

[umadog]

As John says, a UHC should let in more light and may be a better bet. Leave the OIII for later. Most people buy the UHC first, anyway.

I would suggest not worrying about whether it's too narrow. If it's too wide that is bad also. The best thing is to buy a good filter so you can keep it if you upgrade scope. Think about the practicalities: The filter will mean that the useful magnification per unit aperture will go down. That's it: simple. If I remember correctly, it means you will be aiming for the 5x to 10x per inch region. So you'll likely be using the filter at 30x to 60x. The more dark adapted you can get (use and eyepatch) the better: you will be able to operate the higher end of that range. The relatively low power means that you will be using the filter for the larger nebulae such as those in Cygnus (N. America, Veil, Crescent) and those in Sagittarius. It may be useful on the larger planetary nebulae (Dumbell, Owl, Helix). So in practice, you will be using the filter for large objects not small ones. That won't change if you go for a wide pass-band. You'll just end up with a filter that's not so good for the larger objects. Personally, I use this filter: CN Report: The DGM Optics NPB Nebula Filter - CN Report

[crazyjedi]

I don't want to get too wide a band pass filter hence I thought an OIII but didn't want to end up with something too heavy for my scope I hope to upgrade my scope in the next year or two. I'm a little torn as to which way to go with regard to EP and Filter size - 1.25 inch or 2 inch? Right now I only have 1.25inch EP's but was wondering about taking the plunge and going for 2 inch EP's. This obviously would have an impact on the filters I buy so I don't want to buy any new filters until I know which way to go with my EP's but I thought it'd be a good idea to get all the info I could before I make up my mind about anything

[rwilkey]

If you have a 2"-1 1/4" adapter with your scope then you can screw the 2" filter into the adaptor, and use it with 1 1/4" ep's if you want to hedge your bets, the only thing is that 2" filters cost twice as much.