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Baader Narrowband Filter issue?


hograt

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Hi,

I received a set of three narrowband filters - these at 1.25" Ha, OIII, SII manufactured by Baader Planetarium.

I purchased these as they were advertised as being reflection-free and I've seen plenty of images of high standard coming from them.

Last night I was imaging through my William Optics ZS105 Apo / Altair Astro F0.6 FR. See the attached comparison between Ha vs OIII filter / Atik 16HR.  Both images are raw uncalibrated with the same histogram transform applied to give a non-linear image suitable for display.

I've contacted Baader for their assessment - has anyone here seen something similar and/or is there a good reason for this I'm missing?  

Thanks,

Martin

post-405-0-54311700-1439718551_thumb.jpg

post-405-0-81608900-1439718554_thumb.jpg

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Hello,

I use the same filters... Namely the Baader Ha, OIII, SII and H-beta.... I have not seen this happen to any of my filters and I too expose for 30mins and long re per sub.

Even though the halos do point to a problem with the filter, I would first suggest to expose for the same amount of time without the FR on a bright star. I know that your halpha filter is clean, but if the FR happens to scatter bright points of light in the 480-510nm range than it would explain why Ha is clean and OIII is not... Simply Ha would just block the scattering.

Reason why I'm thinking of the FR is because I had a reflection incident on my Hirsch FR.... not halos like what you're getting but arcs in toward the side, seemingly generated by a bright star outside of the FOV. I wasn't seeing the arcs until my exposures were longer than 15-20 mins and each filter showed them, but at different angles, almost as if I was looking at a particular arc on a certain specturm refracted at a different angle.

If its happening without the FR than you know definitely that it's the filter.

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Thanks for the quick response chaps, all input is appreciated!!

MarsG76 - thanks for your time, I'll follow your advise tonight and have a crack without the focal reducer - provided I am blessed with a clear sky two nights running!

I'll post again tomorrow.  Failing that I'm out the country for a couple of weeks and will have another go on my return.

Best regards,

Martin

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here is my first image with the filters taken last week. I did crop the brightest start just on the bottom which had a hint of halo.  Suggests the problem appears above a certain brightness threshold (OIII is blue in false colour spectrum)

post-405-0-19353600-1439723445_thumb.jpg

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I have the same issue. The Baader Ha is very good whilst the OIII gives huge halos and yes they do state "No Reflections" and "No Halos". I had my OIII replaced by Hinds (via Modern Astronomy) but the same issue persists. I also have the same issue with the Blue in the RGB set - once again replaced but the problem persists. Very, very annoying and false advertising by Baader also imo.

My setup is an ATIK 460 and an MN190. I have yet to use these filters through my WO ZS66SD but I am expecting the same problems.

Not very impressed.

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I thought it was only the new Baader LRGB filters that were supposed to be reflection free, unless they've changed the narrow band ones the O111  has always suffered from star haloes, mine has anyway, always had to faff about processing them out.

Dave

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Yep, had halos with my OIII Baader filter as well. Now use Astrodon and problem has gone away. 

There have been a few threads on here about Baader OIII filter halos so I don't think it is a particularly uncommon issue.

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It does seem odd that some, as above, suffer huge halos with Baader Oiii. I have never had any halo issues with any of the Baader filters. I have Ha Oiii Sii and the LRGB set. I use mine with an SXV-H9 and SkyWatcher Newtonians with the Baader Mark II MPCC. I use a Brightstar manual filter wheel.

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  • 5 weeks later...

I had this same problem with Astronomik filters. The blue and the OIII. I contacted Astronomik under their replacement guarantee and they have very quickly replaced all the narrowband filters, OIII,Ha and SII. The Hb they could not as it has been taken out of production. The filters are of the latest manufacture and they recon should not show any halos. They also have promised that when the LRGB are produced with the new coatings I will get replacement ones as well.

As yet I gave not been able to test the narrowband filters.

One thing that may be causing halos is the CCD window, combined with the filters and the FR. It may depend upon spacing between each component. You could try the same image but with a slightly different inter component spacing. If the halo enlarges or reduces then that suggests it is an interaction.

Also if the filters and other components are not pristine as far as surface cleanliness is concerned it also can be a causation, as the coating effectiveness is changed allowing reflections.

Derek

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  • 2 weeks later...

I received a set of three narrowband filters - these at 1.25" Ha, OIII, SII manufactured by Baader Planetarium.

I purchased these as they were advertised as being reflection-free and I've seen plenty of images of high standard coming from them.

Last night I was imaging through my William Optics ZS105 Apo / Altair Astro F0.6 FR. See the attached comparison between Ha vs OIII filter / Atik 16HR.  Both images are raw uncalibrated with the same histogram transform applied to give a non-linear image suitable for display.

I've contacted Baader for their assessment - has anyone here seen something similar and/or is there a good reason for this I'm missing?  

As far as I can tell you haven't sourced your filters from FLO but I have been watching your thread with interest. What was the outcome? :smile:

Yes I've seen that type of thing with the Baader OIII 8nM filter - nowhere near as bad as that though. It seems some optical configurations are worse than others for showing it up.

I use the same filters... Namely the Baader Ha, OIII, SII and H-beta.... I have not seen this happen to any of my filters and I too expose for 30mins and long re per sub.

It does seem odd that some, as above, suffer huge halos with Baader Oiii. I have never had any halo issues with any of the Baader filters. 

The cause of halos has been the subject of much debate and I won't pretend I have a definitive answer but, FWIW, this is my understanding: 

Dichroic filters, like yours, reflect unwanted light whereas absorptive filters absorb unwanted light. Dichroic filters are more popular because they have precise cut-off points and transmit 'slightly' more light. Unfortunately, because they reflect light away from the sensor, dichroic filters are more prone to halos from light reflecting off glass surfaces in front of the filter (a rear optical element, coma corrector, reducer, etc). I suspect this is why some imagers experience halos while others don't, it depends on what is in front of the filter. Baader's anti-halo filters improved things considerably, and in response Astronomik and Astrodon have made improvements to their filters. Which brand is best? I think it depends who you ask and, dare I say, how much they have invested in their chosen brand. Fortunately, thanks to the efforts of Baader and co, halos are less of a problem today than they were a few years ago. But, no manufacturer has 'eliminated' halos. When it happens off-axis stars show offset halos, i.e. bright stars toward the edge of the field of view have halos that are offset to one side of the bright star. If we accept all dichroic filters reflect, some more than others, then offset halos are unlikely to be a 'fault' in the filter. But if the halos are perfectly centred on bright stars, regardless of where they are in the field of view, then, probably, the filter is faulty. 
That is only my opinion and I reserve the right to change it  :grin:
HTH, 
Steve 
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I get a similar problem with the LPAS LP reduction filter, some configurations are fine while others produce horrendous reflections. The worst configuration for me is my 10" SCT with an f/6.3 reducer fitted (the LPAS is just behind the reducer). Whereas my NP127is _without_ reducer is fine (despite the OTA having some optical elements at the rear of the tube). The NP127is _with_ reducer is also a problem.

So yes, reflections from optical elements forward of the filter would seem to be a common problem, but whether this is the same effect I used to see with the Baader filter I have no idea, but if it is - why just the OIII channel? Ha and SII were always OK with no halos.

ChrisH

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I think there is more being discussed here than the anti-reflective properties of filters. The quality of the anti-reflective coatings applied to whatever is in front of the filter also plays a part. I don't know why OIII filters should be more prone, perhaps someone more learned than me can advise :smile: 

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Could you turn the filterwheel around, so the back of the filter is towards the objective (can you even do this with filters?)? That might control the reflections??

They're only designed to work in one direction. The mounted filters obviously can only be fitted one way, but my 50mm square un-mounted filters have a little chevron on the side to indicate which side goes to the front.

ChrisH

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They're only designed to work in one direction. The mounted filters obviously can only be fitted one way, but my 50mm square un-mounted filters have a little chevron on the side to indicate which side goes to the front.

ChrisH

Cool, thanks for confirming.

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More Baader OIII halo problems here, in both the scopes in which we've used them (but camera/FW unchanged.) They are pretty awful, I must say. Since I only want the NB for enhancing LRGB images I can just de-star the OIII and the problem vanishes but this would not be the case for a NB imager.

I'm very keen to switch to an Astrodon OIII but it's Mr O'Donoghue's round!  :grin:

Olly

Edit, I heard rumours of a narrower bandpass OIII from Baader. Any news on this? Baader don't usually leave stones unturned for long.

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Edit, I heard rumours of a narrower bandpass OIII from Baader. Any news on this? Baader don't usually leave stones unturned for long.

I have heard the same rumour, I am meeting the man from Baader tomorrow so will ask him. 

Steve 

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Just a thought :

I have all 2 inch HAOIIISII + UV/IR(LUM)+RGB baader filters and used to them in ED80 with/without the FFR 0.85 and on GSO RC6" with/without the CCDT67 reducer and a combination of SBIG8300 or DSLR's (Canon 350D and Nikon D90).

In all cases whether there was extra glass (flattener - reducer) or not, there has been no halos at all.

Same goes for 2" IDAS LP2 which i sometimes use in combination with RGB + extra glass.

The only filter i have even seen halo from in bright stars is the UHC-S baader but that was a 1.25" filter (and i didnt even had an FFR at the time).

Also of all the images i have personally seen (not that many admittedly) either live or from the web's, where halos occurred the common factor is always the size of the filter being 1.25".

My reasoning could be utterly wrong but 90% of the times the word halo is mentioned it involves a 1.25" size filter :)

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