filter advice

[keiwein1]

so i have an 8se and im looking for some nebula filters... i dont understand which filter i need. do i need 1.25 or 2 inch? i would really love seeing things such as the rossete nebula, great orion, and swan nebula through a filter.
which should i get? THX in advance!
http://www.telescopes.com/collections/telescope-accessories/products/baader-planetarium-o-iii-nebula-telescope-filter?variant=1962894788
http://www.telescopes.com/collections/telescope-accessories/products/baader-planetarium-uhc-s-nebula-telescope-filter?variant=1962896836

[John]

If you use 2" eyepieces you will need 2" filters. The filters you link to are the right sort of thing but there are better performing alternatives such as the Orion Ultrablock or Omega DGM NBP filters (UHC type filters) or the more expensive Lumicon or Astronomik UHC and O-III filters.

O-III filters have more impact on the contrast of nebulae but over a slightly narrower range of target objects than the UHC type filters. Lots of folk end up with both types but perhaps the UHC type would be the best one to get initially.

Some of the objects like the Roseatte Nebula are very large so you might not be able to fit the whole thing in the field of view of your C8 even with a low power, wide angle 2" eyepiece !

[keiwein1]

If you use 2" eyepieces you will need 2" filters. The filters you link to are the right sort of thing but there are better performing alternatives such as the Orion Ultrablock or Omega DGM NBP filters (UHC type filters) or the more expensive Lumicon or Astronomik UHC and O-III filters.

O-III filters have more impact on the contrast of nebulae but over a slightly narrower range of target objects than the UHC type filters. Lots of folk end up with both types but perhaps the UHC type would be the best one to get initially.

Some of the objects like the Roseatte Nebula are very large so you might not be able to fit the whole thing in the field of view of your C8 even with a low power, wide angle 2" eyepiece !

so are UHC filters the same as nebula filter?

[LukeSkywatcher]

First things first. The 8se (which i have also) is a great scope and it can use either 1.25" or 2" eyepieces. Which do you use?. I'm assuming 1.25". 

Correct me if im wrong.

Regarding the filters you mention. Both filters do a certain job (allow different types of light through). The UHC filter enhances the view of certain nebulae (M42 being just one of them). The OIII filter will let you see other nebulae which normally are not visible in a scope without the use of the OIII (such as the Rosette,Veil but to name a couple). The Baader filters are expensive but are apparently top notch. There are cheaper versions (i use the Skywatcher UHC,OIII). They work well for me and my my 8se. I honestly cant say if buying the same for a hundred quid each would be better.

Which one to buy?. I couldnt decide, but knew i wanted to observe the Rosette and Veil...........so i bought BOTH. 

Hope this helps. 

[LukeSkywatcher]

so are UHC filters the same as nebula filter?

Both UHC and OIII filters are nebula filters. Since there are different type of nebulae..............different filters do different jobs and perform differently.As John said.........most people who like to observe nebs (myself included), have both UHC and OIII filters.

[keiwein1]

yeah.... i just measured the ends of the eyepieces that i use and they appear to be at 1.25

thx!

[LukeSkywatcher]

yeah.... i just measured the ends of the eyepieces that i use and they appear to be at 1.25

thx!

Yeah. The 8se comes with a 2" to 1.25" adapter. As new though.........its sold as a 1.25". You can upgrade to 2" visual back if you like. I havent because all my eyepieces are 1.25". 2" eyepieces give a wider field of view.

So you should be looking around for 1.25" filters. Maybe you plan to upgrade your 8se to 2"?. Then you need 2"filters.

Which brand of UHC,OIII is entirely up to you and how much you can afford to spend. 

http://www.firstlightoptics.com/uhc-oiii-visual-filters.html

[Mak the Night]

It is generally considered that the Lumicon filters are the best, I'll probably get their UHC and OIII when I get a 9.25" SCT early next year. I was using the Baader UHC-S to view M42 recently on a 102mm Mak as it is designed to work well with smaller apertures as well as above 150mm. The Baader Neodymium might be interesting for some nebulae as well. 

http://www.firstlightoptics.com/light-pollution-reduction/baader-neodymium-filter.html

[LukeSkywatcher]

It is generally considered that the Lumicon filters are the best.

I must admit that Lumicon is a name which i see come up most often by VERY seasoned astronomers here on SGL in relation to "which filter?".

[laudropb]

Li icon are certainly amongst the best, but they are expensive. I have the Skywatchers UHC and OIII and they work just fine for me. I do agree that you need both to find a range of different types of Nebulae.

[Mak the Night]

It is generally considered that the Lumicon filters are the best.

I must admit that Lumicon is a name which i see come up most often by VERY seasoned astronomers here on SGL in relation to "which filter?".

I have discussed filters all over the Net, including with David Knisely, and the Lumicons are generally the most favoured. There's a bit of a paucity of them at the moment but I'll probably get some next year. The Astronomik are also deemed good. I need more aperture to get the best out of Lumicons though. The Baaders I have work well from what I can observe with a 4" Mak. Although the UHC-S darkened the sky around M42 more than the Neodymium did I could actually see more nebula cloud in comparison to no filter. Which was interesting. I believe the Baaders work well with apertures under 150mm, which isn't probably true for other filter makes.

[John]

so are UHC filters the same as nebula filter?

Some good advice above, since I last posted in the thread.

The filters we are discussing enhance the contrast in nebulae. Well, to be accurate, they don't add anything but they filter out unwanted bandwidth leaving those that are primarily emitted by the nebulae so they dim surrounding objects and make the nebulae stand out a bit more.

They don't do anything for galaxies and clusters and dark skies are the best enhancer of deep sky objects whether filters are being used or not.

[Mak the Night]

I believe UHC stands for 'Ultra High Contrast' and CLS 'City Light Suppression'. Some filters appear to have a combination of filter profiles and differ slightly from different manufacturers. The Baader UHC-S is not unlike the Explore Scientific CLS in its graphic filter profile, both filters possibly being designed to be more versatile.

http://www.baader-planetarium.de/sektion/gemeinsame_dateien/download_filter/filter_uebersicht_en.pdf

Lumicon make Deep Sky, Hydrogen-Beta, Oxygen III, and Ultra High Contrast Filters.

http://www.lumicon.com/pdf/3filterspec_prnt.pdf

As with all things astronomical YMMV.

[John]

The UHC filter was developed by Jack Marling of Lumicon. Others have since used the term of course

The Baader UHC-S is close to being a broadband rather than a narrowband filter which filters such as the Lumicon UHC, Orion Ultrablock etc are. It was developed to be useful in small aperture scopes but for an 8" aperture I feel a full blown UHC-type and / or an O-III will prove more effective on suitable target objects.

Just to add another filter category, the O-III and H-Beta filters are termed "line filters".

[Mak the Night]

I wonder what the difference between the Lumicon 'Deep Sky Filter' LF3010 and the Lumicon ‘Ultra High Contrast Filter’  LF3025 is? It seems to me that the 'Deep Sky Filter' is more versatile and would act not unlike the Baader UHC-S.

I'm not confused at all lol! 

[jetstream]

The newest Astronomiks are tested individually versus batch testing- they are very good. My 1.25" Astro Hb might be deemed too wide by some but it shows the appropriate objects very well. The main thing is having a filter that is not too wide and that doesn't clip the desired "bandpass". I'm very hesitant to get rid of my Astronomik OIII as it shows some faint nebs better than the Lumi OIII and UHC... ie SH2-157

Dark skies bring out the best in filters... regardless of aperture.IMHO.

[Mak the Night]

I think aperture is an important factor with filters though. I live in the greenbelt and generally have quite good dark skies, but I'd be reluctant to use a very narrow band filter with anything below 130mm at the very least. Lumicon and other manufacturers often recommend that their filters are best used on 150mm or above.

[John]

I frequently use my O-III filter with my 102mm refractor. The views of the Veil Nebula using it and the 31mm Nagler are one of the highlights of my observing year. My back yard has some light pollution issues, depending where you point the scope

[Dave In Vermont]

As a resident 'filter-nut' who has 36 filters in his collection(s), the question often arises of: "UHC or OIII first?" Passionately debated and discussed, the answer works out to the same: 'Toss a coin.' 

And I've noted people often change their opinions over the days & nights(John).

Both will open up new vistas in remarkable ways -

Dave

[YKSE]

My limited experience agree with John's and Gerry's observations.

I'm not sure that I've read anything about recommended aperture for nebulas from Lumicon, Lumicon does recommend exit pupil size in their filter guide here (page 4 and 5) and as we can see there, the narrow the bandwidth(deep sky broadest, H-beta narrowest), the larger recommended exit pupil size, meaning lower magfications. And it's actually easy to understand, since filters block some spectrum of light, things get dimmer, therefore we need have larger exit pupil to have better surface brightness.

With the same size of exit pupil, an 8" shows the same brightness of an extended object(a nebula) as a 4", the difference is that 8" shows the object twice as big as in 4". Our eyes need to see a certain size (2' to 3') of an feature to reconize it, therefore an 8" perceives to be brighter since we see more details in 8", while those features are too small in 4".

Many Nebulas are quite big, Veil e.g. is over 3°, I had no difficult to see it with my starter scope 130p in my light-polluted backyard, even with UHC and a 32mm plossl.

[Mak the Night]

I frequently use my O-III filter with my 102mm refractor. The views of the Veil Nebula using it and the 31mm Nagler are one of the highlights of my observing year. My back yard has some light pollution issues, depending where you point the scope

Do you think I'd get similar results with a 102mm Mak? I always thought refractors tended to outperform reflectors when it came to light gathering. I could obtain an Astronomik OIII filter relatively easily (unlike the Lumicon invisible pink unicorn filter lol) especially as you and others seem to rate the Astronomik as highly or more so than the Lumicon. I've seen what I can of the veil unfiltered with my Mak and my Newt. I'm intrigued that it might be worth using an OIII on a 4" Mak and getting good results. 

http://www.astronomik.com/en/visual-filters/oiii-filter-visuell.html

It was this bit in the Astronomik blurb that put me off.

'Since enough light must be available to make use of the OIII filter it is best to use this filter with apertures of more than 6" (150mm). Smaller instruments do not gather enough light for meaningful and satisfying astronomical work.' ~ op cit 

The more I think about this the more confused I become. I wish I could buy a filter that would make thinking about buying a filter clearer lol.

[Mak the Night]

My limited experience agree with John's and Gerry's observations.

I'm not sure that I've read anything about recommended aperture for nebulas from Lumicon, Lumicon does recommend exit pupil size in their filter guide here (page 4 and 5) and as we can see there, the narrow the bandwidth(deep sky broadest, H-beta narrowest), the larger recommended exit pupil size, meaning lower magfications. And it's actually easy to understand, since filters block some spectrum of light, things get dimmer, therefore we need have larger exit pupil to have better surface brightness.

With the same size of exit pupil, an 8" shows the same brightness of an extended object(a nebula) as a 4", the difference is that 8" shows the object twice as big as in 4". Our eyes need to see a certain size (2' to 3') of an feature to reconize it, therefore an 8" perceives to be brighter since we see more details in 8", while those features are too small in 4".

Many Nebulas are quite big, Veil e.g. is over 3°, I had no difficult to see it with my starter scope 130p in my light-polluted backyard, even with UHC and a 32mm plossl.

I'm gonna have to read up about exit pupils. I've found some information online but I'm not sure what it means. AFAIK the exit pupil is calculated by the eyepiece f/l divided by the telescope f/r. So my 4" Mak (f/12.7) would produce an eye relief of approx 2.5mm with a 32mm Plossl. 

[jetstream]

I'm gonna have to read up about exit pupils. I've found some information online but I'm not sure what it means. AFAIK the exit pupil is calculated by the eyepiece f/l divided by the telescope f/r. So my 4" Mak (f/12.7) would produce an eye relief of approx 2.5mm with a 32mm Plossl. 

Thats the issue right there Mak, the 2.5mm exit pupil- my OIII's ( I have both the Lumi & Astronomik) want more exit pupil. 4mm minimum really and 5mm is VG. For LP skies the Lumicon is perhaps better- but it seems fussier to exit pupil, it likes a bit bigger than the Astronomik.

Small aperture scopes, like my 90mm frac do well with the OIII, if the EP mag (exit pupil) is matched to the filter.

Your Explorer 130 f5 might surprise you on nebs with an OIII (easier to get the exit in the right range).

ps I just read your sig- that 25mm TV plossl, the 130 F5 + an OIII would work pretty good...

[Mak the Night]

Thats the issue right there Mak, the 2.5mm exit pupil- my OIII's ( I have both the Lumi & Astronomik) want more exit pupil. 4mm minimum really and 5mm is VG. For LP skies the Lumicon is perhaps better- but it seems fussier to exit pupil, it likes a bit bigger than the Astronomik.

Small aperture scopes, like my 90mm frac do well with the OIII, if the EP mag (exit pupil) is matched to the filter.

Your Explorer 130 f5 might surprise you on nebs with an OIII (easier to get the exit in the right range).

ps I just read your sig- that 25mm TV plossl, the 130 F5 + an OIII would work pretty good...

Thanks, that's very interesting. Although I'm pretty sure my Explorer is f/6.9 (900/130). I have read that a rough guesstimate to magnification strength with filters is to count a factor of about 10x magnification for every inch of aperture to ensure a bright enough image. I get 40.6x with a 32mm Plossl with my Mak, although I still would get that 2.5mm exit pupil.

[jetstream]

Yes there are confusing reports about filter use, I have tried all my EP's with them from 32mm-3.5mm and can say that the exit pupil issue is real and is about the best way to get things working together for good OIII views. Sorry about your scope FL, I wasn't exactly sure which one you had.

I think there might be something to the "volume of light" (aperture) deal but the main thing is the exit pupil IMHO. You can always try one with the Skymax to see how it works. Reflectors are excellent for filter use, I think it is a myth that refractors are assumed better in this regard.