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I hate my OIII filter

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#1 Epox75

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Posted 27 June 2020 - 10:57 PM

I have a Baader 1.25 inch narrowband set, SII at 8nm, Ha at 7nm and OIII at 8.5nm. I am used to image with an ASI1600MM-Cool at 200 gain / 50 offset, using 2 minutes exposures at f/4. 

With SII I usually get 250-400 ADU above bias, with Ha 350-500, with OIII 650-800. If I compare the exposures from the 3 filters, OIII is always noisier and often shows background gradients, especially if I don't integrate much data. I image from a light polluted sky (bortle 6/7)

 

The Baader OIII ultra narrowband at 4.5nm started to get my curiosity.... will going narrower solve/reduce my problem? Will I be able to combine SII 8nm, Ha 7nm and OIII 4.5nm without visible issues? 

 

A last question: how's the Astronomik OIII at 6nm? I might try a completely different brand at this point.

 

Thanks, 

 

Andrea 


Edited by Epox75, 27 June 2020 - 11:11 PM.


#2 Aaron_tragle

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Posted 27 June 2020 - 11:02 PM

OIII always has more gradients and noise, did you shoot during the moon by a chance? Moon absolutely destroys OIII data.


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#3 Epox75

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Posted 27 June 2020 - 11:10 PM

OIII always has more gradients and noise, did you shoot during the moon by a chance? Moon absolutely destroys OIII data.

No, I am already past paying for trying OIII under the Moon. It seems that it gets much more light than the other filters, also when I take flats with the shirt I have to take OIII at a different time compared to Ha and SII. Those two, instead, go along quite well. 



#4 skyward_eyes

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Posted 27 June 2020 - 11:32 PM

8.5nm is pretty broad for OIII. You would like get better results going narrower. Under 5nm is ideal, 3nm if you can swing it. 


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#5 andysea

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Posted 27 June 2020 - 11:32 PM

That makes sense, red light doesn't scatter as much as the shorter wavelengths of the blue/green spectrum. 

I use a 3nm OIII.

For OIII I think it makes sense to get the narrowest band pass available.


Edited by andysea, 27 June 2020 - 11:33 PM.

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#6 jamesNewmanF125

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Posted 27 June 2020 - 11:42 PM

Former Baader user turned Chroma 3nm user here, I echo what folks are saying about it being too broad. 

 

Any reason why you don't change your exposure times per filter?



#7 Epox75

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Posted 27 June 2020 - 11:45 PM

8.5nm is pretty broad for OIII. You would like get better results going narrower. Under 5nm is ideal, 3nm if you can swing it. 

 

That makes sense, red light doesn't scatter as much as the shorter wavelengths of the blue/green spectrum. 

I use a 3nm OIII.

For OIII I think it makes sense to get the narrowest band pass available.

Thanks! That's good to know, after two years with this filter I am looking for something even slightly better. 



#8 Epox75

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Posted 27 June 2020 - 11:51 PM

 

Any reason why you don't change your exposure times per filter?

I did it sometimes in the past, at 90sec. I got less noise and gradient but not much, I ended up preferring the ease of calibration (same darks). Anyway integrating a certain amount of data, let's say 4 hours seems to yields acceptable results in terms of gradient/noise. Still I would like a filter that goes better along with the other two. 


Edited by Epox75, 28 June 2020 - 12:02 AM.


#9 Der_Pit

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Posted 28 June 2020 - 05:44 AM

As for trying a different brand:  Be careful if you use an OAG for guiding.  The Astronomik filters are thin (1mm) and might cause a substantial focus shift compared to thicker filters that would knock your guide cam out of focus....


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#10 Epox75

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Posted 28 June 2020 - 07:05 AM

As for trying a different brand:  Be careful if you use an OAG for guiding.  The Astronomik filters are thin (1mm) and might cause a substantial focus shift compared to thicker filters that would knock your guide cam out of focus....

Thanks for the advice, that's good to know.. but isn't proper to put the OAG before a narrowband filter or guiding in narrownband it's actually a thing with advantages and such ? 



#11 Der_Pit

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Posted 28 June 2020 - 07:14 AM

Thanks for the advice, that's good to know.. but isn't proper to put the OAG before a narrowband filter or guiding in narrownband it's actually a thing with advantages and such ? 

Yes, that is exactly the problem.  The OAG is before the filter, so it doesn't see the focus shift the filter creates┬╣.  If you have a filter with different thickness, you have to refocus the telescope to have the main camera in focus - and that will de-focus the guide cam in the OAG....

 

┬╣ A filter of thickness L will shift the focus by ~L/3


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#12 Epox75

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Posted 28 June 2020 - 07:20 AM

If you have a filter with different thickness, you have to refocus the telescope to have the main camera in focus - and that will de-focus the guide cam in the OAG....

 

True, I didn't think about that. I'm not using an OAG yet but I have it and I will use it for sure in the future so thanks for the advice. 



#13 JoeR

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Posted 28 June 2020 - 07:34 AM

F/4 is not ultra fast like Hyperstar and RASA optics, but still may be too fast for 5nm and 3nm filters. IMO 8.5nm is probably a better choice for your OTA because of the loss in transmission due to the center wavelength shift. I use it on my Hyperstar systems and the 1600MM & 178MM with good results. Granted it does require more processing efforts and sky conditions have to be good, nothing past a 70% moon or bortle class 5 skies. The 1.25" filter size may be an issue too. I have an Orion 1.25" LRGB set with noticeable vignetting on my 1600MM. So they are limited to planets and I use Baader 2" LRGB & NB for DSOs.


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#14 Epox75

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Posted 28 June 2020 - 03:07 PM

F/4 is not ultra fast like Hyperstar and RASA optics, but still may be too fast for 5nm and 3nm filters. IMO 8.5nm is probably a better choice for your OTA because of the loss in transmission due to the center wavelength shift. I use it on my Hyperstar systems and the 1600MM & 178MM with good results. Granted it does require more processing efforts and sky conditions have to be good, nothing past a 70% moon or bortle class 5 skies. The 1.25" filter size may be an issue too. I have an Orion 1.25" LRGB set with noticeable vignetting on my 1600MM. So they are limited to planets and I use Baader 2" LRGB & NB for DSOs.

I see,  F/4 it's only with my newton, my refractor goes at F/4.7 with the reducer and I have an 8'' inch Ritchey Chretien and a C11 so I might get the 4.5nm filter and just keep them both.  


Edited by Epox75, 28 June 2020 - 03:08 PM.


#15 Astrobarn_

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Posted 29 June 2020 - 02:16 AM

I hate my Baader OIII as well for halos mostly.
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#16 OldManSky

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Posted 29 June 2020 - 01:38 PM

I hate my Baader OIII as well for halos mostly.

I tried to like the Baader OIII 8.5nm.  I really did.

But contrast was low, halos were extreme...after 9 months I tossed it and tried the Optolong OIII 6.5nm filter.

No halos.  No gradients.  Good contrast.  

No more Baader :)


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#17 jtrezzo

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Posted 29 June 2020 - 02:35 PM

I hate my Baader OIII as well for halos mostly.

Had the same problem. No more Baader narrowband filters for me, especially the OIII.


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#18 Epox75

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Posted 29 June 2020 - 03:51 PM

I hate my Baader OIII as well for halos mostly.

 

I tried to like the Baader OIII 8.5nm.  I really did.

But contrast was low, halos were extreme...after 9 months I tossed it and tried the Optolong OIII 6.5nm filter.

No halos.  No gradients.  Good contrast.  

No more Baader smile.gif

Optolong seems like a good choice with its 2mm thickness. Did you change the whole filter set or just the OIII?

 

Had the same problem. No more Baader narrowband filters for me, especially the OIII.

Yeah, I guess it's time to change then. The Ha thou seems to be a pretty good filter. 


Edited by Epox75, 29 June 2020 - 07:44 PM.


#19 Peregrinatum

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Posted 29 June 2020 - 03:54 PM

OIII is always noisy, goes with the territory.



#20 OldManSky

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Posted 29 June 2020 - 06:31 PM

Optolong seems like a good choice with its 2mm thickness. Did you change the whole filter set or just the OIII?

 

Yeah, I guess it's time to change then. The Ha thou seems it's a pretty good filter. 

My narrowband set is a "mutt":  ZWO 7nm Ha, Astronomik 6nm S2, Optolong 6.5nm OIII.

I didn't care about a matching set, and these all have no halos and good contrast/performance :)


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#21 sn2006gy

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Posted 29 June 2020 - 09:53 PM

My narrowband set is a "mutt":  ZWO 7nm Ha, Astronomik 6nm S2, Optolong 6.5nm OIII.

I didn't care about a matching set, and these all have no halos and good contrast/performance smile.gif

This is good info :D



#22 RJF-Astro

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Posted 30 June 2020 - 01:59 AM

Another former Baader user who went for Chroma 3nm. It really makes a big difference, although O3 will remain difficult compared to Ha. But I can now image O3 before and past astronomical sunset, something I could not do with 8.5nm. Also the Chroma filters have not produced any noticable halos so far, while I did have halo issues with Baader on brighter stars.

 

The Baaders gave me a good introduction to narrowband, but if you use narrowband a lot and want the best results, maybe it is time to move on.

 

Focus shift on my OAG is an issue though. I cannot combine (ZWO) RGB and narrowband withouth refocussing the OAG.



#23 Pete_xl

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Posted 30 June 2020 - 08:20 AM

I have abandoned my 36mm unmounted ringy Baader 8.5nm OIII in favor of a Chroma 3nm. What a difference! I now have in the filter wheel a 7nm Baader, a 8 mm Baader SII,  the Chroma OIII and a CLS/RGB set. All are without halos an I'm happy now. I have a lot of focus difference between the Baaders and the Chroma but the measured offset distances within the Baader set that Baader claims to be parfocal were too big to ignore anyway. I use the NINA autofocus routine to refocus after each filter change in the sequence and everything works fine.


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#24 TareqPhoto

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Posted 30 June 2020 - 10:23 AM

Andrea, how about you gave me your Ha data of a target you choose using your GSO 6" and i will add it to my OIII data? This way we will see how good or bad it can be, or donate your Ha for me and i will donate mine of OIII, what do you think?

 

I follow your Telescopius posts, very nice, i wasted last 2 years with not ideal filters even for Ha although i already have Astrodon Ha 5nm since 2017, but i use QHY camera which is requiring 36mm filter size so i coudn't have high quality better filters for that, and that is why i ordered ASI1600mm to get back to 1.25" filters as i already added 3nm [OIII/SII] so far.



#25 Epox75

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Posted 30 June 2020 - 02:57 PM

I have abandoned my 36mm unmounted ringy Baader 8.5nm OIII in favor of a Chroma 3nm. What a difference! I now have in the filter wheel a 7nm Baader, a 8 mm Baader SII,  the Chroma OIII and a CLS/RGB set. All are without halos an I'm happy now. I have a lot of focus difference between the Baaders and the Chroma but the measured offset distances within the Baader set that Baader claims to be parfocal were too big to ignore anyway. I use the NINA autofocus routine to refocus after each filter change in the sequence and everything works fine.

I'll put the Chroma on my list but that's a bit too expensive for me now, I've recently contracted the Apitis and I'm saving money for fairly large triplet to use during the next galaxy season :)  If the Optolong doesn't give gradients or halo I would rather get that one.  And I agree that NB Baader arent' parfocal. For CLS you mean the Astronomik one? I am looking for an LP filter to replace my Lumicon Deep Sky that also gives some halo. 




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