OIII filter

[Knighty2112]

Hi all. Pondering getting a decent OIII filter to use, but will I see any benefit really in my main ST120 frac at at which is my main scope I use? From what I've read it is 6" and above scopes that benefit from the filter, so this may show promise in my Celestron C6-N reflector perhaps. Any experience/views from anyone who may have an ST120 or C6-N scope would be welcome, and also I've heard that the astronomic OIII filter are very good, so any advice as to which are good/bad makes would be great too! Thanks!

Oh! Suffer from moderate LP where I live too, and have a UHC Explore Scientific filter already. 

[Knighty2112]

Hmmm......just read Astro-Baby's review on both OIII & UHC filters. Seems like UHC may have the upper hand, but crucially she couldn't spot the Veil with either of them, and could see it without the filters instead! Puzzling?  

http://www.astro-baby.com/reviews/O111 and UHC filters/O111 and UHC Filter Review.htm

[John]

When I use my O-III with my 102mm F/6.5 refractor it shows the Veil Nebula wonderfully well. With my 31mm Nagler I can get both the E & W portions in the same FoV and on a decent night I see the Pickerings wisp section as well. It's one of THE best sights in visual astronomy for me and certainly the best of the Summer months

My UHC will show the nebula but not anywhere near as well as the O-III does. Without the filter (same viewing conditions) only the brightest section of the Nebula is visible and even then only very vaguely and faintly.

I can't speak highly enough of the impact of the O-III filter on this and similar objects. For a few years my only deep sky filter was an Astronomik O-III.

 

[Mark at Beaufort]

Last night I was using both my Orion VX8, but more important for your question I was also using a 72mm APO frac. I installed my Astronomik O-III into my E.S. 68 degree EP giving me a FOV of 3 degrees 47' in the Altair Lightwave. I was able to just see both main parts of the Veil. The part surrounding star 52 was a bit faint but I knew from previous experience what I was looking for. So a O-III will work very nicely in your ST120.

However, I would recommend an Astronomik O-III over the Lumicon O-III because the latter darkens the sky a lot more so IMHO the Lumicon is better in much larger scopes.

[Knighty2112]

9 hours ago, John said:

When I use my O-III with my 102mm F/6.5 refractor it shows the Veil Nebula wonderfully well. With my 31mm Nagler I can get both the E & W portions in the same FoV and on a decent night I see the Pickerings wisp section as well. It's one of THE best sights in visual astronomy for me and certainly the best of the Summer months

My UHC will show the nebula but not anywhere near as well as the O-III does. Without the filter (same viewing conditions) only the brightest section of the Nebula is visible and even then only very vaguely and faintly.

I can't speak highly enough of the impact of the O-III filter on this and similar objects. For a few years my only deep sky filter was an Astronomik O-III.

 

Sounds great John. What is the effect of LP on the filter though? I'm assuming your skies are pretty good to see the Veil?

[Knighty2112]

7 minutes ago, Mark at Beaufort said:

Last night I was using both my Orion VX8, but more important for your question I was also using a 72mm APO frac. I installed my Astronomik O-III into my E.S. 68 degree EP giving me a FOV of 3 degrees 47' in the Altair Lightwave. I was able to just see both main parts of the Veil. The part surrounding star 52 was a bit faint but I knew from previous experience what I was looking for. So a O-III will work very nicely in your ST120.

Sounds promising indeed! I guess I am a little weary that without good dark skies then it won't add much more to what I can already see with the UHC filter I have. 

[Mark at Beaufort]

9 minutes ago, Knighty2112 said:

Sounds promising indeed! I guess I am a little weary that without good dark skies then it won't add much more to what I can already see with the UHC filter I have. 

Its difficult to comment on this because I have pretty good skies. I agree with John that on the Veil the O-III brings out a lot more detail. I also viewed the Veil in the 8" Orion with a Skywatcher UHC and although I could see both parts of the Veil it was not as good as the O-III.

[John]

14 minutes ago, Knighty2112 said:

Sounds great John. What is the effect of LP on the filter though? I'm assuming your skies are pretty good to see the Veil?

LP diminishes the effect of the filters as it does when no filter is used. Under really dark skies (which mine are not really !) the filters show even more but they help where there is some LP around as well.

 

[Knighty2112]

Thanks guys. I guess the short of it is that I won't really know unless I get one and see!  

[nicoscy]

Here's an EXCEL sheet showing what filter on which object. Feel free to sort however you like in EXCEL...

Filters list of objects.xlsx

[Knighty2112]

6 minutes ago, nicoscy said:

Here's an EXCEL sheet showing what filter on which object. Feel free to sort however you like in EXCEL...

Filters list of objects.xlsx

Thanks for the list. Very interesting!  

[Knighty2112]

Just worked out that my current Scientific Explore UHC filter allows aprox about a 50nm window for OIII, whereas the astronomic OIII filter allows aprox a 20nm window for OIII light, plus none of the H-alpha light starting at 635nm is allowed through like the UHC filter allows. 

[John]

3 minutes ago, Knighty2112 said:

Just worked out that my current Scientific Explore UHC filter allows aprox about a 50nm window for OIII, whereas the astronomic OIII filter allows aprox a 20nm window for OIII light, plus none of the H-alpha light starting at 635nm is allowed through like the UHC filter allows. 

What is your conclusion from that ?

 

[Knighty2112]

5 minutes ago, John said:

What is your conclusion from that ?

 

I guess the conclusion from that is that the filter should block out more unwanted light to give a darker contrast to the light allowed through, so in theory should result in better views of the Veil, planetary nebulas etc. Fingers crossed!  

[BGazing]

Watched Veil tonight, and compared UHC and OIII through Hyperion 31, so in my scope it is EP of around 2,8mm, at 71x. Sky was wonderfully transparent, but the local light source reduced SQM reading to 21.05 (the sky is otherwise very very dark...difficult to explain).

Anyway, used both DGM NPB and OIII. I love DGM, it is absolutely great on a number of objects, but Veil is for OIII. And Veil is worth the price of the OIII alone. My OIII is a TS one, not the most expensive, but it does the job. It is good on planetary nebulae too.

Wish i had a decent widefield 40mm with me...OIII requires more light than I can supply atm, but a 40mm Paragon is already in the post...

[jetstream]

I've found the Lumicon OIII more sensitive to exit pupil than the Astronomik OIII, but does offer more contrast on many things. The Astronomik is VG and on some faint things shows more, but then my excellent Lumicon UHC ( lucked out) is the perfect companion to the Lumicon OIII.  The jury is still out on the Lumicon Hb...

Making comparisons using a filter slide is a huge benefit IMHO.

[Mark at Beaufort]

23 minutes ago, jetstream said:

I've found the Lumicon OIII more sensitive to exit pupil than the Astronomik OIII,

Gerry when you are using the Lumicon O-III what exit pupil are you preferring. I often wonder whether an exit pupil in the 6 range might be worth experimenting. I have a 30mm EP which in my 12" Dob gives an exit pupil of just under 6 although I have never tried it preferring the 24mm and 20mm.

[jetstream]

Hi Mark, I find that the 4.8mm exit pupil of the 21mm Ethos as an excellent minimum and the 6.25mm exit pupil of the 30mm ES 82 an excellent maximum. Below that minimum I find that the Lumicon OIII gets fussy and more object dependent. For my new little newt 200mm f3.8 I wanted a VG exit pupil using the 21E-5.5mm and leave room for the 25mm ES 100 which will give a 6.5mm exit pupil.

For objects like the North American nebula my 30mm ES 82 is in the focuser a lot... the extra TFOV and image "brightness" with this set up is excellent IMHO, but dark skies are needed. I would definitely try your 30mm on these large objects with the Lumicon OIII.

[Mark at Beaufort]

Thanks Gerry that is very interesting and useful. I am hoping that the clear skies will stay in the UK for a few more days so I will give it a go tonight. My skies are reasonably dark so I should get some interesting results. Thanks again for your information.

[Piero]

I have the Astronomik OIII (and UHC) and it has always worked well in my 60mm refractor with 24mm eps (4.0mm exit pupil). Yesterday under 20.6mag, it gave me a lovely view of the Veil nebula (east, west, pickering's triangle and 2 more faint vertical filament in the centre). The North America also looked very pretty with the same filter with a marked contrast around the Mexican Gulf. I have used it down to 1.2mm exit pupil for spotting some planetary nebulae with no problem (as long as the planetary nebulae were accessible with my 60mm of course!).

The UHC is somehow more versatile and works better to enhance the nebula extension in my opinion. So, I tend to prefer it on M42 as well as the Nebulae at North of Sagittarius.

Under a moderate light polluted sky, I would get an OIII rather than an UHC, personally. Under darker skies, well, to me the choice is more down to user preference and target type. Some target, e.g. the Veil and Owl nebulae, really stands out with an OIII filter.

Great filters! 

[BGazing]

On 07/08/2016 at 21:45, Piero said:

I have the Astronomik OIII (and UHC) and it has always worked well in my 60mm refractor with 24mm eps (4.0mm exit pupil). Yesterday under 20.6mag, it gave me a lovely view of the Veil nebula (east, west, pickering's triangle and 2 more faint vertical filament in the centre). The North America also looked very pretty with the same filter with a marked contrast around the Mexican Gulf. I have used it down to 1.2mm exit pupil for spotting some planetary nebulae with no problem (as long as the planetary nebulae were accessible with my 60mm of course!).

The UHC is somehow more versatile and works better to enhance the nebula extension in my opinion. So, I tend to prefer it on M42 as well as the Nebulae at North of Sagittarius.

Under a moderate light polluted sky, I would get an OIII rather than an UHC, personally. Under darker skies, well, to me the choice is more down to user preference and target type. Some target, e.g. the Veil and Owl nebulae, really stands out with an OIII filter.

Great filters! 

a post worth revisiting.

two nights ago we had an all-nighter under LP skies (20.06). turned out OIII was of more use than DGM NPB which I loved under the dark skies (SQM 21 and more). even pushed OIII to 180x plus on M42 and it worked well (M42 was low and in LP), so it is worth experimenting.

@Piero, Astronomik OIII is comparable to Castell OIII when it comes to bandpass? I plan to buy a 70mm APO, already have Castell UHC 1.25 filter, so I'm thinking whether to keep it and add an OIII complement or redo the 1.25 line...how does the bandpass affect smaller aperture? should i go softer than for c8?

[YKSE]

11 hours ago, BGazing said:

@Piero, Astronomik OIII is comparable to Castell OIII when it comes to bandpass? I plan to buy a 70mm APO, already have Castell UHC 1.25 filter, so I'm thinking whether to keep it and add an OIII complement or redo the 1.25 line...how does the bandpass affect smaller aperture? should i go softer than for c8?

I don't think Castell OIII comes close to Astronomik, Castell OIII is very wide, have a look at Reiner's measurement here:

http://www.reinervogel.net/index.html?/Filter/Filter_OIII.html

The stars will not be dimmed as much in a wider filter, but the nebula constrast is less enhanced than a narrow one. My understanding is that with a narrow-band filter, you're intend to see the nebula, not the stars, so narrower band width and higher transmisison are preferred, IMHO. Smaller aperture has smaller image size than large ones, but the same brightness with the same exit pupil, therefore loss of small details (because of too small image size), but it'll frame larger ones better, for large nebula with low surface brightness, it should be advantage to frame it for seeing the constrast against neighboring field.

[BGazing]

33 minutes ago, YKSE said:

I don't think Castell OIII comes close to Astronomik, Castell OIII is very wide, have a look at Reiner's measurement here:

http://www.reinervogel.net/index.html?/Filter/Filter_OIII.html

The stars will not be dimmed as much in a wider filter, but the nebula constrast is less enhanced than a narrow one. My understanding is that with a narrow-band filter, you're intend to see the nebula, not the stars, so narrower band width and higher transmisison are preferred, IMHO. Smaller aperture has smaller image size than large ones, but the same brightness with the same exit pupil, therefore loss of small details (because of too small image size), but it'll frame larger ones better, for large nebula with low surface brightness, it should be advantage to frame it for seeing the constrast against neighboring field.

thanks! castell uhc at 49mm is really wideband. given that i plan to use the small apo with a 1.25 diagonal, i'm thinking of a dgm npb in 1.25 and some OIII filter (dgm again, or teleskop service)...

has anyone tried dgm oIII filter? ts OIII numbers look just a bit under astronomik in those measurements (that is why i got the 2 inch one)...for less money...

[nicoscy]

I think it is important to clarify. If you want the best contrast for nebulae then get the narrowest band one you can get. Exit pupil governs brightness and not the bandpass of the filter. If you want some stars to show up as well and lose some contrast on nebulae, a wider bandpass will provide this.

However since we all use filters to enhance nebulae, then the narrower the bandpass the better. You can use a filter in any size scope, it doesn't matter. What comes through is related to the exit pupil of the scope. Obviously for the same exit pupil there may be a different magnification for each instrument, hence a varying level of detail and resolution available.

[YKSE]

I've not used DGM OIII, the reviews I've read are not that positive for that saving (4€ cheaper than Astronomik?).

I've used TS OIII and Skywather OIII, TS OIII was clearly better Skywather's, the skywather OIII showed the Veil less good than TS UHC! If you really want to go budget solution, TS OIII is a better choice. Their 1.25" filter thread is better done than their 2" ones too.