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Do you experience halos with your imaging setup?

Baader H-alpha Ultra-Narrowband 3.5nm (CMOS-Optimized) 36 mm Filters NGC7635 Deep Sky Nebula
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Does your imaging train in combination with the h alpha filter produce halos on bright(er) stars?
Multiple choice poll 51 votes
24% (12 votes)
29% (15 votes)
10% (5 votes)
37% (19 votes)
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Tobiasz avatar
Tobiasz avatar
Hello, 

I got the Baader SHO Ultra-Narrowband Set second hand with a good discount and already had some clear skies to test them out extensively (including NINA's automatised filter offset calculation). 

After that I did some 600 and 900 second test exposures of the bubble nebula in Ha/Oiii/Sii to see if I experience any halos. I read in the internet, that Baader's Oiii can be prone to halos. No issue on that one, but the H alpha filter showed some ring-like Halo around the mag 7 double star near the bubble.

I asked Baader and they said it can be that my flattener in combination with the filter and the camera glas that produces the halo. 

My question would be do you use the filter and experience halos, too? I am interested if this is a rare or more common phenomenon. 

This is my first mono setup and the first time that I have filters which produce halos, so it would be nice to know if you have any guidelines or postprocessing tips to reduce/remove them properly. 

Regards.
Tobiasz
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Ruediger avatar
Ruediger avatar
Hi Tobiasz,

The O3 tend to have light halos. The Ha and S2 are usually not prone to.
BUT: In the beginning there were batches of mall-coated filters. They were exchanged on request by Baader. If the person, from who you have purchased your filters, were one of the concerned buyers, but did not exchange it, you may have a batch of bad ones.
Especially O3 had an serious production flaw on its start. It was tackled 6-9 months later after many complaints. I exchanged mine too.

CS
Rüdiger

PS: Halos are very much depended to your setup. Spacing and f-ratio are important factors, which could make the difference between halo or no halo. So the statement from Baader is definitely true.
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Michael Ring avatar
Michael Ring avatar
Was also a victim of the out of spec baader filters, in my case the High Speed filters for F2.0
I had to provide the original bill and the whole set was exchanged… This was also a bulk replacement for a number of Baader Filter customers….
Ryan Génier avatar
Ryan Génier avatar
I have a set of Baader Ultra-Narrowband filters for F2. The Ha and Oiii are perfect, no halos. However I have recently picked up the Sii to fill out the set, and I have bad halos with that one. I might contact them….
Christoph Nieswand avatar
Christoph Nieswand avatar
I do have the same filters and experience the same halos: more often at OIII but rarely on very bright red stars also at H alpha.
And it is definitively true, the setup is crucial. Any potentially reflective surface in the optical path might contribute to generating halos.
And the flattener is certainly a good candidate.
There are formulas around, which allow for a good guess how distant the contributing surface is measured from the sensor or filter. But I do not have it at hand right now.
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Dan Watt avatar
Dan Watt avatar
I have the Antlia 36mm Highspeed Pro 3nm Filters in OIII and HA. They are used with my qhy268m + Nexus reducer on a 6" f4 newt and an 8" f4 newt bringing them to F3. So far I have not seen any halos out of either.
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Marko avatar
Marko avatar
I do not have your filter, but an Optolong L-Ultimate. On my Askar V I dont see halos, on my Samyang 135 I do with some stars. Therefore It also seems depend on the actual telescope.
On the Samyang I mounted the Filter in front of the objective, which creates back reflections of the sensor on my image, especially when I take flats with a white panel.  Depending on the angle and exposure time you can see the border of the chip. If the filter has slight transmission at certain wavelength and any reflective surface inside the optical path introduces a bit of curvature to the wavefront, this might explain out of focus ghost images of the star or halos, especially with small f-ratios. The fact that narrowband filters are basically very good mirrors for every wavelength than the one they are made for, does not help for sure.
I now pushed a 31mm UV/IR filter in the back of the Samyang, which fits perfectly like it is made for that, but did not find time to test that. If the problem is IR, I hope this also works as well as for him:
https://www.astrobin.com/forum/c/astrophotography/other/the-cause-and-the-elimination-of-halos-around-stars-with-some-duo-narrowband-filters/
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Oscar avatar
Oscar avatar
not using Baader here, but Antlia LRGB V-pro, SHO 3nm, and no halos, F/5
Rob Kiefer avatar
Rob Kiefer avatar
I do have the ultra-narrowband CMOS optimised Ha, OIII and SII filters. On certain stars I get halos. Interesting to read that they exchanged the filters (earlier production problems). I accepted that the filters show halos on certain occasions. They are very fairly priced (in comparison to some other brands). Would be interesting to compare these to the newer batches. 
Robert
MaksPower avatar
MaksPower avatar
I bought an Antlia 2" quad-band filter which had shocking halos to the point of being unusable. All stars affected.
After a few outings concluded it really was garbage and trashed it, and won't buy that brand again, ever.
Tony Gondola avatar
Tony Gondola avatar
In my dual band work I have noticed that halos, if present, always show up in the OIII channel but not Ha.
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Tobiasz avatar
Tobiasz avatar
I am astonished, that only 1/3 of the participants of the poll do not experience any halos at all. As I started mono imaging recently I thought this problem is rarer than it is discussed in the forums. But I am wrong and halos are a more widespread "feature" of filters. Because it affects only my Ha Filter; I will accept accept it for now and try to process them out.

Thank you for your input.