narrowband filters

[Whippy]

Nebulas, lovely things but my understanding is that a narrowband filter would enhance my viewing pleasure. An OIII filter is the obvious choice as a fair few nebula emit 'light' at that wavelength, and filters being filters it would er, filter out any light except the OIII wavelength correct (also, seems like the only one on sale that's a sensible price!)? Am I also correct in saying that smaller scopes wouldn't benefit because of their lack of light gathering capabilities?

So would my 8" bring in enough light for an OIII filter to show itself off? And with these things costing £50 and upwards, do they make that big a difference? And while we're at it, any recommendations on what's the weapon of choice?

[John]

I use 2 Baader narrowband filters, a UHC-S and and OIII. The UHC-S is very effective and works with small scopes like my ED80 as well as larger ones. The 0III is even more effective, especially on nebulae but is really too severe in the 80mm scope - you can see the nebula OK (M57 in this case) but all the background stars are filtered out. It is most effective with my C8 which gathers a lot more light of course.

If you can afford just on narrowband filter my advice would be to go for the UHC-S. If you can run to 2 than get an OIII as well but you won't use it as much.

John

[SteelRat]

First time I saw anything of the Viel neb was through an Astronomik UHC-E filter 8)

Think the Baader UHC-S is cheaper and is well liked by owners.

[Kaptain Klevtsov]

Check this guy out, really good deals on filters which are left over from production runs for the big boys I suspect. Keep looking as he changes what's on offer from time to time.

http://stores.ebay.co.uk/BJOMEJAG-EBUYER-STORE_Astronomical-FIlters_W0QQcolZ4QQdirZQ2d1QQfsubZ2QQftidZ2QQtZkm

Fast delivery from the USofA as well.

Captain Chaos

[Astroman]

I generally recommend against an OIII in favor of the UHC-S. OIII works very well on very few objects, but the UHC works very very well on many many more.

[maroon bells]

Think the Baader UHC-S is cheaper and is well liked by owners.

I would agree with that. I was testing mine out on the Orion nebula a couple of months ago and it made a very noticable difference.

[SteveL]

can someone explain which wavelengths these different filters allow (or block)?

[Kaptain Klevtsov]

can someone explain which wavelengths these different filters allow (or block)?

In what way explain?

The name of the filter describes the wavelength of light that it will allow through, so a OIII filter lets through light given off by an emission nebula for example.

UHC and similar filters let groups of emmission line light through plus some of the rest of the light so they are more useful for visual stuff as they let more of the starlight through.

If you want to know the actual wavelength of the emission lines, try the Baader Planetarium website as it has graphs of the light pass against wavelength for most of the filters.

If you want to know what emission line filter works best with each target, try here http://pages.sbcglobal.net/raycash/filters.htm

Captain Chaos

[Macavity]

Companies like Baader often publish fairly reasonable plots of the transmission charateristics on their websites. Failing that, it's usually possible to find them (somewhere!) on the following site:

http://www.astroamateur.de/filter/

I always think of "Contrast" filters passing Red, Green and Blue and stopping the intermediates. Ultra High Contrast as simply "more so" in that general vein.

[Whippy]

Interesting link KK, gives a good rundown over quite a few objects .

[Merlin]

I remember seeing somewhere that the BAADER UHC-S filter lets through too much light compared to other narrowband filters. Can anyone confirm?

[John]

I remember seeing somewhere that the BAADER UHC-S filter lets through too much light compared to other narrowband filters. Can anyone confirm?

Well it is not as "severe" as some of the other narrowband filters but that is what makes it so useful in smaller aperture scopes. It's certainly much more effective than the Orion broadband filter that I used to use.

You could argue that other narrowband filters let though too little light which makes them less useful in smaller apertures. If you have a large scope this won't be an issue of course.

John