Advice required for essential filters

[Hairycamel]

Hi all,

I'm a bit of a newbie and am seeking advice on kitting myself out with some filters. My initial thoughts on reading various musings are to start with a Baader Neodymium for Moon/lpr reduction and a Skywatcher UHC filter for DSO enhancment. I will be starting to image with DSLR shortly but I also have a Meade LPI. Has anyone any thoughts on any more "must haves"?

[Andrew*]

A UHC and an LP reduction filter sounds like a very good start. The UHC is mainly a visual filter, while the LP filter tends to make a more effective difference in imaging.

The Neodymium is an interesting filter, and I would say worth trying on almost any target, whether DSO, under light pollution or even on the planets.

If you really get into viewing nebulae, the OIII filter is an excellent second filter to the UHC, but perhaps that can wait as it's that bit more specialised...

Andrew

[Hairycamel]

Thanks Andrew, it's a bit of a minefield out there for the uninitiated...

[rwilkey]

I would say the UHC and OIII are excellent filters for visual observing, what telescope will you be using them with? The OIII is better in larger apertures.

[Andrew*]

The OIII can be used to great effect in smaller apertures too. I've heard of people using them with the 7mm naked eye, but I have had a great result using one on an 80mm viewing the veil nebula for example.

I think some don't like OIIIs so much because they can make the view very dim, with an ink-black background sky and very dim, greenish stars, although the nebula should remain bright, and of course smaller aperture adds to that effect.

[tom714uk]

The OIII is better in larger apertures.

I've read this a few times - but where does "large" start? For a 10" at a site with little light pollution, is an OIII going to be better than a UHC, or will it be annoyingly dim? I don't mind if the stars are dim or green when I'm trying to look at a nebula, it's just the nebula itself I'm interested in. (Besides, OIII light is green, that's the whole point surely!)

Cheers,

Tom

[Andrew*]

Yes, that's the point. An OIII blocks every colour except the small portion of green light that contains the OIII emission line.

If the telescope is large enough to show the nebula, then it's large enough to use an OIII! The OIII doesn't block any nebulosity (except Hb, which is where the UHC comes in).

To me it doesn't make sense to say an OIII is better in larger apertures as everything is better in larger apertures!!

[tom714uk]

Thanks Andrew. I'd assumed that the idea was that an OIII is less satisfying to view through than a UHC with aperture < x, but better than a UHC with aperture > x, because its narrower bandpass reveals finer detail but requires more light throughput to get a satisfactorily bright image.

x will presumably vary somewhat between observers. However, I was wondering if 10" was generally considered to be higher or lower than a typical value of x...

Tom

[Andrew*]

I would say 10" is on the large side. Often people say 8"+ is better for OIII filters.

But more importantly, it depends on the target: an OIII and a UHC do slightly different things, no matter what the scope. The UHC passes Hb as well, which is present in different nebulae. Check this out: The Prairie Astronomer

Andrew

[tom714uk]

But more importantly, it depends on the target: an OIII and a UHC do slightly different things

That's true as well. Thanks again Andrew.

Tom

[Hairycamel]

In reply to rwilkey, I'm using a 8" F10 SCT in my back garden which, according to need-less is LV Mag 5.4. Given this info, UHC or OIII or both?

[MjrTom]

In reply to rwilkey, I'm using a 8" F10 SCT in my back garden which, according to need-less is LV Mag 5.4. Given this info, UHC or OIII or both?

Both

Eight inches is more than enough aperture

[Hairycamel]

That's what I like to hear! As I said in a previous post, savings and disposable income are overrated!

[rwilkey]

I agree with all of the above, I have used both in different apertures, great for nebula observers.