Filters: What do they do?

[Raph-in-the-sky]

Hello everybody,

I am new to astronomy... I just got my first "real" telescope a few days ago. I'm not considering buying filters right now however I'm curious and I will probably buy filters someday.

The question I wanted to ask is what are the most commonly used filters, what do they do and what are they good for? Let's stick to the ones that help observing (astrophotography is not going to be a concern for the time being)

From what I understood UHC filters are great and should be the first one I get but then they are so many other filters I would like to know about...I heard about OIII, neodymium, H alpha, H beta, CSL, color filters of all kind and so on! I'm getting lost...

Raph

[Ben the Ignorant]

They absorb or reject some colors while letting other colors through, so the contrast between lit areas and darkened areas becomes stronger.

[lenscap]

Have you read this thread?

 

[Stargazer33]

Hi,

This is from Flos' website:

The narrowband UHC filter, like the O-III filter, isolates the two doubly ionized oxygen lines (496 and 501nm) in addition to the hydrogen-beta line (486nm) emitted by planetary and most emission nebulae.

The UHC filter permits superb views of objects like the Orion, Lagoon, Swan and other extended nebulae. It performs well in smaller aperture instruments owing to its greater light transmission than the O-III, yet still suppresses light pollution well.

The UHC filter is the best all-round dark-sky nebula filter.

The neodymium and CLS are light pollution filters. They help block stray light from the old sodium type street lights etc.

Coloured filters help to bring out features on the various planets, such as the cloud hands on Jupiter, as well as the Great Red Spot; the albedo (dark areas) features on Mars, or cloud detail in Venus's atmosphere.

HTH

[Raph-in-the-sky]

29 minutes ago, lenscap said:

Have you read this thread?

 

Thanks that is exactly what I was looking for !

[johninderby]

BTW the Baader Neodynium filter isn’t just a light pollution filter but the best planetary filter for Jupiter and Saturn I’ve ever used. Great on mars too and gives the moon a nice neutral,colour as well as increasing contrast. 

[TareqPhoto]

I have OIII and UHC but didn't waste time to use them much, didn't know how to use them at all, but i do have Baader Neodymium filter, great in visual with my Mak on the moon and planets, but i do imaging mostly so i don't focus much on visual filters anyway, i tried this Baader Neody filter for imaging, wasn't bad actually, but someone keep telling me that it is NOT the right filter for the moon and planets, so i will try not using it and keep it only for visual.

[Stu]

14 minutes ago, johninderby said:

BTW the Baader Neodynium filter isn’t just a light pollution filter but the best planetary filter for Jupiter and Saturn I’ve ever used. Great on mars too and gives the moon a nice neutral,colour as well as increasing contrast. 

I would argue that the Neodymium Filter IS just a light pollution filter, it just happens to be very good at improving contrast on the planets. I have found it particularly useful on Jupiter when observing during twilight conditions, and as said on the moon and Mars. It might be a personal preference but I like Saturn better without it.

This site lists some useful comparisons showing which deep sky filters work best on which targets.

https://www.prairieastronomyclub.org/filter-performance-comparisons-for-some-common-nebulae/

One thing to remember is that all filters reduce the amount of light reaching your eye, so for deep sky observing with IHC and OIII filters etc, good dark adaptation is still important.

[LukeSkywatcher]

5 hours ago, Raph-in-the-sky said:

Hello everybody,

I am new to astronomy... I just got my first "real" telescope a few days ago. I'm not considering buying filters right now however I'm curious and I will probably buy filters someday.

The question I wanted to ask is what are the most commonly used filters, what do they do and what are they good for? Let's stick to the ones that help observing (astrophotography is not going to be a concern for the time being)

From what I understood UHC filters are great and should be the first one I get but then they are so many other filters I would like to know about...I heard about OIII, neodymium, H alpha, H beta, CSL, color filters of all kind and so on! I'm getting lost...

Raph

The best advice i got when deciding between UHC and OIII was:

"UHC makes the already visible (M42 etc), more visible. OIII , makes the invisible,visible (The Veil,Rosette etc)".

I couldnt decide, so i bought both. Skywatcher branded.

Ive owned coloured filters, and i cant see they make any difference. Moon filter, you really dont need as its not dangerous to look at a full moon. Its a personal thing.

The one type of filter you dont want to get wrong is a solar filter.

[Raph-in-the-sky]

5 minutes ago, LukeSkywatcher said:

The best advice i got when deciding between UHC and OIII was:

"UHC makes the already visible (M42 etc), more visible. OIII , makes the invisible,visible (The Veil,Rosette etc)".

I couldnt decide, so i bought both. Skywatcher branded.

Wouldn’t the OIII obstruct too much light for my Skywatcher 130/900?

[LukeSkywatcher]

12 minutes ago, Raph-in-the-sky said:

Wouldn’t the OIII obstruct too much light for my Skywatcher 130/900?

With OIII, (as with any fiter) its all about blocking/letting certain light waves through. Ive happily used an OIII on a 130mm scope. OIII filters really only come into play on nebs that are not visible through an unfiltered scope. Also, the nebs that OIII work on are the one you cant see with the naked eye. If you can see a neb (in a scope naked eye)................a UHC filter is good................it enhances the detail.

UHC= enhancing the already visible.

OIII = making the invisible,visible.

 

[Martin63]

On 31/07/2018 at 13:45, LukeSkywatcher said:

With OIII, (as with any fiter) its all about blocking/letting certain light waves through. Ive happily used an OIII on a 130mm scope. OIII filters really only come into play on nebs that are not visible through an unfiltered scope. Also, the nebs that OIII work on are the one you cant see with the naked eye. If you can see a neb (in a scope naked eye)................a UHC filter is good................it enhances the detail.

UHC= enhancing the already visible.

OIII = making the invisible,visible.

 

I am not doing AP, would a UHC or OIII filter be worth my hard earned dollars? I am a newbie, but I do love finding Messier objects!

[John]

10 minutes ago, Martin63 said:

I am not doing AP, would a UHC or OIII filter be worth my hard earned dollars? I am a newbie, but I do love finding Messier objects!

Hi and welcome to the forum.

What scope do you have ?

 

[Martin63]

4 minutes ago, John said:

Hi and welcome to the forum.

What scope do you have ?

 

Orion SkyQuest XT8 PLUS Dobsonian, I have 8mm, 25mm and 35mm eyepieces - nothing fancy yet. I live in San Diego and have a decent southern view; it has the least amount of light pollution. 

[John]

Both the UHC and the O-III type filters will work fine with your scope. They improve the contrast of nebulae. No benefit for galaxies or clusters. Objects such as the Veil Nebula get a noticable boost, especially with the O-III filter.

Which to go for ? - if it were me I'd pick an O-III such as the Astronomik or Lumicon because of the impact that filter has. UHC's are a bit more subtle but do help with a slightly wider range of targets so there is a case to be made there as well. Most people say go for the UHC first but my experience says O-III.

 

 

[niallk]

+1 for an O-III to purchase first.

For my 10", I have a filter wheel, allowing me to flick between no filter, O-III, UHC, medium density (lunar).  It is super handy for nebulae.  BTW, I have colour filters but don't use them.

[refractordude]

My widest aperture scope is a 120mm f/8 refractor. The best filter for me is gasoline. I love a long drive to a bortle 3 or 4 campsite. The country side around where I live is beautiful. 

https://darksitefinder.com/maps/world.html