Filters for nebula

[ckp82]

I've only ever imaged galaxies when doing e.a.a. What kind of filter would I need to pick out nebulas? The only filter I own is a svbony ir/uv cut filter.

Thanks.

[Steve in Boulder]

I’m assuming you’re using a one-shot color (OSC) camera, right?   It depends on the nebula.  If it’s a reflection nebula like the Iris Nebula, NGC 7023, then your UV/IR cut filter (or no filter at all) is best, because the nebula reflects broad-band light from a nearby star.  If it’s an emission nebula like the Eagle Nebula, M16, then a dual narrowband filter is best, because the emitted light mostly lies in the narrow H-alpha and OIII bands.  If you’re happy with Svbony, they make a relatively inexpensive dual narrowband filter.

[ckp82]

Thanks for replying @Steve in Boulder

So for reflective nebulas I wouldn't need a filter and for emmision nebulas I would need a dual narrowband filter. 

For planetary nebulas and super novas like the crab nebula for example, would I need a different type of filter all together? There seems to be a few types of nebula and alot of different filters.

Thanks.

[Steve in Boulder]

A dual narrowband filter will work great on planetary nebulas like M27 and supernova remnants like M1.  Both have strong H-alpha and OIII signals.  The main thing you lose out on with a dual narrowband filter and an OSC camera compared to monochrome imaging is the ability to capture SII signal, which is present in, for example, M1.  You can get a dual narrowband filter that lets through SII and OIII, but for now that’s more the realm of AP than EAA.  

[ckp82]

Thanks again @Steve in Boulder

So for galaxies and reflective nebulas leave the filter off and put it on for the other nebulas if they contain H-alpha and/or 0lll signals.

I don't know if I could progress to astrophotography, it's enough learning the basics of e.a.a!

My camera is an osc camera.

 

[Steve in Boulder]

You got it!  

[PeterC65]

As @Steve in Boulder has mentioned, your UV/IR cut filter, or better still, no filter, would be the best option for reflection nebulae. But there are relatively few of these and most nebulae are emission nebulae of one form or another. For these nebulae you could use a dual narrow band filter but you should be able to observe many of them with your existing UV/IR cut filter.

If you decide to get a dual narrow band filter I would go for one with narrow bands that are on the relatively wide side. I use the Optolong L-eNhance for example which has a 25nm pass band covering H-beta and both the OIII emissions and a 10nm pass band covering H-alpha. Narrower pass bands cut out too much light for EAA I think and are better suited to AP.

The FLO web page about the L-eNhance filter gives a useful with and without comparison image of what it can do.

 

[ckp82]

Thanks for your suggestion.

I've had a look at the options and at the moment I'd like to keep the costs low so I've decided on either the optilong l-eNhance or the ZWO dual narrowband filter. Other than the price point (£30 cheaper), ZWO has become a brand I like and trust, having the asiair plus and Asi585mc camera.

Technical charts and jargon goes over my head, so out of these 2 filters is one better than the other or are they the same quality and do they do the same job equally?

Thanks again.

[PeterC65]

The ZWO filter has slightly wider pass bands than the Optolong. Anything wider than the wanted emission peaks (which is what the Optolong passes) is letting through unwanted background noise which is a disadvantage. ZWO are also known for their cameras and harmonic mounts whereas Optolong are known for their filters.

Having said that, one of my main criteria when buying filters is to keep them parfocal so that I don't need to refocus when I change filters (I have an electronic filter wheel), and for that your filters all need to be the same thickness and preferably from the same manufacturer.

[ckp82]

Thanks @PeterC65

I'll go with optolong then if they specialise in filters.

[AstroMuni]

On 01/08/2024 at 11:39, ckp82 said:

Thanks @PeterC65

I'll go with optolong then if they specialise in filters.

Take a look at the Antlia triband RGB filter. Many of my friends use it for EEVA and get good results.

See this review...https://www.skyatnightmagazine.com/advice/multi-band-filters-astrophotography

Edited August 2 by AstroMuni

[ckp82]

3 hours ago, AstroMuni said:

Take a look at the Antlia triband RGB filter. Many of my friends use it for EEVA and get good results.

See this review...https://www.skyatnightmagazine.com/advice/multi-band-filters-astrophotography

Thanks for replying Astromuni, but I have already ordered the optolong.

[AstroMuni]

On 02/08/2024 at 19:26, ckp82 said:

Thanks for replying Astromuni, but I have already ordered the optolong.

I have heard good things about Optolong filters, so you should be ok 🙂