Visual filters

[bosun21]

What’s the general consensus on filters as an aid to visual astronomy?.As I’ve fairly recently resumed my astronomical journey ,with my previous foray being many years prior. There seems to be a filter for all occasions. Light pollution, contrast, nebula etc. Are these worth looking at?, or are they just a gimmick?

[Jiggy 67]

They are well worth looking at and definitely not a gimmick, I use them regularly. I don’t know what scope you use but I would recommend the following:

OIII and UHC for nebulae, especially planetary. Both can work, but sometimes the UHC works where the OIII doesn’t dependent on your aperture as an OIII can dim the image

Baader Contrast Booster- Great on planets

Baader Moon and Skyglow-good all round LP filter

Woudn’t be without any of the above

[John]

I have tried quite a number of different filter types over the years including coloured ones, lunar ones, planetary ones and various broadband, narrowband and line filters for the deep sky. The ones I have ended up with for nighttime use are excellent quality O-III, UHC and H-Beta filters for nebulae. The H-Beta is limited in it's use but has shown me the Horsehead Nebula. The O-III and UHC filters (branded Lumicon and Astronomik) really do enhance the contrast of a range of nebulae, the O-III significantly so. I have the O-III and UHC filters in both the 2 inch and 1.25 inch sizes.

When I am observing the sun in white light with my Herschel Wedge I use the required neutral density filter fitted within the wedge and a single polarising filter on the end of the eyepiece.

I tend to prefer not to use a filter (except for solar observing of course) but when I do I want it to make a real impact so I've stuck with those that have done that for me.

 

 

 

Edited November 20, 2021 by John

[bosun21]

2 minutes ago, Jiggy 67 said:

They are well worth looking at and definitely not a gimmick, I use them regularly. I don’t know what scope you use but I would recommend the following:

OIII and UHC for nebulae, especially planetary. Both can work, but sometimes the UHC works where the OIII doesn’t dependent on your aperture as an OIII can dim the image

Baader Contrast Booster- Great on planets

Baader Moon and Skyglow-good all round LP filter

Woudn’t be without any of the above

I have an 8” Dobsonian and a 127 Maksutov. I read about the different types and bought a 1.25” UHC. I was going to buy the Baader Neodymium, is that the LP filter that you mentioned? or is the moon and sky glow different. Finally is the Baader contrast booster called the same?. Sorry for all the questions 

[Jiggy 67]

Just now, bosun21 said:

I have an 8” Dobsonian and a 127 Maksutov. I read about the different types and bought a 1.25” UHC. I was going to buy the Baader Neodymium, is that the LP filter that you mentioned? or is the moon and sky glow different. Finally is the Baader contrast booster called the same?. Sorry for all the questions 

Yes the Baader neodymium is the moon and sky glow filter and yes, just search for Baader contrast booster. I really like this filter on Saturn and Jupiter as it makes the band’s really stand out, a lovely filter.

 I use my UHC (Astronomik) more than the OIII (also Astronomik) just because the OIII has a narrower pass band which means it can really substantially dim what is already, probably, a dim object. The UHC isn’t as narrow so doesn’t cause as much as a problem. An 8 inch reflector is just about ok with the OIII, it has the aperture to deal with it but I don’t think I would use an OIII with a smaller aperture, I’ve tried it on my 4 inch refractor without much luck

[bosun21]

6 minutes ago, Jiggy 67 said:

Yes the Baader neodymium is the moon and sky glow filter and yes, just search for Baader contrast booster. I really like this filter on Saturn and Jupiter as it makes the band’s really stand out, a lovely filter.

 I use my UHC (Astronomik) more than the OIII (also Astronomik) just because the OIII has a narrower pass band which means it can really substantially dim what is already, probably, a dim object. The UHC isn’t as narrow so doesn’t cause as much as a problem. An 8 inch reflector is just about ok with the OIII, it has the aperture to deal with it but I don’t think I would use an OIII with a smaller aperture, I’ve tried it on my 4 inch refractor without much luck

Thank you, it’s very helpful 

[John]

I use my O-III filters with my 102mm refractor and they work excellently. The Veil nebula, with this scope and filter is one of my favourite deep sky targets.

Edited November 20, 2021 by John

[Franklin]

18 minutes ago, Jiggy 67 said:

Finally is the Baader contrast booster called the same?

The Baader Contrast booster filter is a combination of the Baader Neodymium filter(moon + skyglow) and an aggressive minus violet filter. Stronger than the similar Semi-Apo filter, the Contrast Booster was originally intended for use with budget achromatic telescopes, to help cut out the chromatic abberation that these scopes exhibit. It is a very useful filter, the neodymium substrate is quite subtle but blocks light pollution and general skyglow and also glow from the moon, whilst the minus violet blocks unfocused light in non-apo scopes. The fact that it darkens the image somewhat turns out to be quite useful as a glare reducer when observing the moon and brighter planets. It does what it says, boosts contrast. But not on deepsky objects. OIII and UHC filters are useful in boosting contrast on emission nebula, planetary nebula and supernove remnants. Stellar objects like galaxies, open and globular clusters are better viewed without a filter IMO.

[callisto]

43 minutes ago, Jiggy 67 said:

An 8 inch reflector is just about ok with the OIII, it has the aperture to deal with it but I don’t think I would use an OIII with a smaller aperture, I’ve tried it on my 4 inch refractor without much luck

Yes, I second that 

 

Mark.

[PeterC65]

I'm quite new to astronomy and I was sceptical about filters but I took the plunge and tried some out.

I'm most impressed with the Astronomik UHC filter. It significantly darkened the sky around M42 allowing me to see more of the nebula and more of its structure. From what I've read, UHC filters seem to be better than OIII filters when used with smaller aperture telescopes as they don't block quite so much light (I have a Skymax 127). Be aware that not all filters described as UHC are the same. The Astronomik UHC filter just lets through the parts of the spectrum emitted by nebulae (OIII and H alpha and beta) but others are more wideband and so less effective.

I have the Baader Neodymium Moon and Skyglow filter and that does increase contrast slightly for all objects by taking out some of the background sky glow but I'd say the difference is only marginal.

The other filter I find useful is a Baader Neutral Density filter which I use to observe the Moon. It cuts out 90% of the light which reduces the glare when observing the Moon and lets me see more detail. I won't look at the full Moon now without this filter as it blinds me.

I've had some benefit from a blue filter (W80A), when observing Jupiter it brings out the cloud bands a little but also turns the planet blue which I don't like. I haven't yet found the red filter (W25) useful, but then Mars hasn't been visible to me so far.

I have all these filters in a filter wheel which makes swapping them in and out very easy, to quickly check whether they make a difference.

Edited November 20, 2021 by PeterC65

[Stu]

1 hour ago, Jiggy 67 said:

An 8 inch reflector is just about ok with the OIII, it has the aperture to deal with it but I don’t think I would use an OIII with a smaller aperture, I’ve tried it on my 4 inch refractor without much luck

I’ve used my OIII filter with a range of smaller scopes, 72mm is the smallest I think. Provided you are reasonably well dark adapted they work very well. I love the views of the Veil and NAN through my four inch scopes; particularly my Genesis with a 31mm Nagler gives a lovely wide 5 degree field allowing you to view the whole of these objects in one go. The trick is to keep the mag fairly low so you still have a good sized exit pupil, then the views remain bright enough.

[Franklin]

10 minutes ago, Stu said:

The trick is to keep the mag fairly low so you still have a good sized exit pupil

That explains exactly how to use an OIII filter.

[Kon]

As a newbie in this hobby, I got a televue OIII filter for my 8" Dob based on recommendations from this forum. I have fairly dark skies and even the Veil is visible without one but the filter makes it pop better. I have found it useful for the low surface brightness nebulas that makes them standout more. I prefer the unfiltered views for most of the brighter nebulas and I tend not to use it as often. I usually use low magnification with it. With your choice are you fighting light pollution or want things to stand from the background? I also have a polarising filter for the moon since my wife does not like the brightness close to full moon, again I prefer unfiltered views. I found the polarising one useful on Jupiter one night when seeing was okish since it brought up some of the bands. Reading through reports and reviews try go for a good quality one 

[Stu]

3 hours ago, PeterC65 said:

From what I've read, UHC filters seem to be better than OIII filters when used with smaller aperture telescopes as they don't block quite so much light (I have a Skymax 127).

The challenge with Maks is the long focal ratio which gives smaller exit pupils, so an OIII may well give dim images. Even a 40mm eyepiece only gives a 3.4mm exit pupil, but that may well help a little vs a 32mm at 2.7mm

[Tim]

It's a great question

Also worth remembering that not all filters are created equal. I just assumed they were when I started looking for them for my dobs, I have a 10" and an 18", and got myself a Baader Oiii and a cheap UHC filter, maybe a Skywatcher one, but I cant remember now. The performance was underwhelming to say the least, and the Baader Oiii was a little too dark for my liking, even in the larger Dob. In fact I compared it side by side with my Baader Oiii imaging filter and there wasn't a massive difference.

Being able to try a selection of filters out at star parties made a big difference for me, and over the years I have settled on three old Lumicon filters, UHC, my favourite, a bright Oiii, and a Hb filter. The Hb has a much more limited range, but used on the North American nebula for instance it knocks the socks off the other filters. Sadly the original Lumicon brand filters are out of production now, but they come up every now and again on the used sites.

If you can find quality used filters you can probably try them and sell them on if you don't like them without losing too much of what you paid for them.

Tim

[bosun21]

1 hour ago, Stu said:

The challenge with Maks is the long focal ratio which gives smaller exit pupils, so an OIII may well give dim images. Even a 40mm eyepiece only gives a 3.4mm exit pupil, but that may well help a little vs a 32mm at 2.7mm

I just added a 40mm plossl for this reason as previously i was maxing out with my 32mm. Being a relative newcomer to astronomy, i think that the entire question of exit pupil is overlooked by most beginners 

[PeterC65]

12 hours ago, Stu said:

The challenge with Maks is the long focal ratio which gives smaller exit pupils, so an OIII may well give dim images. Even a 40mm eyepiece only gives a 3.4mm exit pupil, but that may well help a little vs a 32mm at 2.7mm

I have a 40mm Celestron Omni which I bought specifically to get the maximum exit pupil from the Skymax 127. I've also just bought an ES 68 degree 24mm to compare it with. The ES is a wider angle EP and so gives a more emersive view, but I've not had it long enough to determine whether the smaller exit pupil makes a difference. Unfortunately I've still not been able to see the Vail (with or without filters), which is one of the targets I'd most like to observe!

[Zermelo]

Unfortunately, the Baader contrast filters recently succumbed to the widespread price rises (I was looking to buy one, but took too long deciding). There is a comparison of their characteristics here (and also covers their effectiveness in dealing with CA, for achromat users).

I agree with the comments above about the importance of maximizing the image brightness when using the OIII (or other line filters) - I have sometimes struggled with my OIII, but the UHC has always been OK in that respect.

1 hour ago, PeterC65 said:

Unfortunately I've still not been able to see the Vail (with or without filters)

The Veil was the one that really showed me what a good nebula filter could do. I couldn't see anything at all without it (Bortle 4 with 6" reflector) but it was very obvious with my UHC. With some other objects, you can see them very well without a filter, and while you may not see a greater extent of nebulosity with a filter, you can sometimes see different areas that weren't apparent without one.

Another contemporary thread discussing filters:

 

[UKDiver]

15 hours ago, bosun21 said:

I just added a 40mm plossl for this reason as previously i was maxing out with my 32mm. Being a relative newcomer to astronomy, i think that the entire question of exit pupil is overlooked by most beginners 

I think that there are far too many subjects to consider for most newcomers to get it all sorted in their minds. Something will give.

[Stu]

13 hours ago, PeterC65 said:

Unfortunately I've still not been able to see the Vail (with or without filters), which is one of the targets I'd most like to observe!

Don’t forget that even with your 40mm eyepiece you will on get sections of the Veil in in one go, and they may be dimmer. The 102 f7 being discussed elsewhere is capable of showing the whole lot in one go, assuming a suitable eyepiece. In these snapshots from SkySafari the outer ring is a 102mm with 31mm 82 degree eyepiece, whilst the smaller ring is the Mak.

[PeterC65]

21 minutes ago, Stu said:

Don’t forget that even with your 40mm eyepiece you will on get sections of the Veil in in one go, and they may be dimmer. The 102 f7 being discussed elsewhere is capable of showing the whole lot in one go, assuming a suitable eyepiece.

I had another look for the Veil tonight but it was unfortunately behind a tree!

I also tried comparing the Celestron 40mm (3.4mm exit pupil) and the ES 68degree (2mm exit pupil) on M31 and M42 (also using an Astronomik UHC filter for M42). I could just about persuade myself that the additional light from the larger exit pupil showed slightly more detail in both cases, but I preferred the 'bigger' view provided by the ES EP I think.

M45 is one of my main drivers for considering a wider field scope. The Mak just can't take it all in.

[bosun21]

2 hours ago, PeterC65 said:

I had another look for the Veil tonight but it was unfortunately behind a tree!

I also tried comparing the Celestron 40mm (3.4mm exit pupil) and the ES 68degree (2mm exit pupil) on M31 and M42 (also using an Astronomik UHC filter for M42). I could just about persuade myself that the additional light from the larger exit pupil showed slightly more detail in both cases, but I preferred the 'bigger' view provided by the ES EP I think.

M45 is one of my main drivers for considering a wider field scope. The Mak just can't take it all in.

When I bought my 127 Mak I already knew it’s strengths and weakness’s regarding the relatively small FOV. It’s for this reason I complemented it with an 8” Dobsonian. Between these two I’ve got more than enough to keep me busy whilst gaining more knowledge about the hobby. I am also in the process of saving for an astrophotography setup which will probably be an EQ6-R pro with either a doublet or triplet. The point I’m trying to make is that it’s horses for coarses with telescopes, target types etc

[bosun21]

I am just going to place my order for filters. Is the general consensus that the astronomic UHC is the way to go? For a second it’s either a Baader Neodymium or a Baader contrast booster. Thoughts anyone 

[PeterC65]

From the research I did, the Astronomik UHC filter is the UHC to get. That's the one I have and I'm very happy with it.

[John]

UHC followed as rapidly as possible by an O-III

Astronomik is a good brand to aim for.