Upgrading narrowband filters: is it worth switching from 7 mm to 3nm?

How much light pollution are you dealing with? If you’re not at a dark site, then generally the narrower the better. And, even at a dark site, narrower will allow better imaging with the moon out.

I have the Antlia Edge 4.5nm filters as well as Chroma 3nm. They are both solid with no halos. I used to use the Zwo 7nm and, yes, they have halos on Oiii, but they were inexpensive. To me, the Antlias are the best bang for the buck, with high transmission and no halos. Chromas are simply the best, but cost as such.

Dave Stirling · May 28, 2026, 03:03 PM

Nikhil · May 28, 2026 at 05:02 AM

Hello all.

With galaxy season coming to a close, I've started a narrowband project for my monochrome camera. With only preliminary data, I noticed a severe problem with my ZWO OIII 7 mm filter. It seems to produce terrible halos around bright stars (I’ve included the images below) and this is apparently a very common problem with this filter. I've upgraded to the Antlia OIII 3 nm filter and I'm waiting for it to arrive.

I wanted to ask experienced people in the community, do you think it's worth it to upgrade my other Ha and SII 7 nm narrowband filters while I'm at it? Those filters don't seem to produce artifacts but I'm mainly asking with regards to the benefit of going to a smaller bandpass.

Thanks very much for your input!

📷 1000012068.jpgfirst image description: HOO image of zeta oph. Very noticable halo around the bright central star.

📷 1000012062.jpgsecond image description: same as first image but only Ha data. No noticeable artifacts.

I think halos are a function of the quality of the filter rather than the bandpass. You would likely see improvement in halos around OIII specifically with the higher quality filter, so it would be interesting to see how much halos diminish by swapping out the OIII with the new filter you’ve ordered first. Highly recommend 3nm for high light pollution (I’m in Bortle 6).

That would make sense that halos depend on filter quality.

Judging from your’s and the previous commenter’s inputs it seems that a 3 nm bandpass won’t make too much of a difference since I am at a dark site.

Thanks for sharing your experience!

Tighter filter bandpass = better contrast = longer exposures = you’ll need better guiding

Most all NB targets are comprised of Ha therefore you can get a quicker, faster final stacked result just shooting/stacking a lot of Ha subs regardless of LP or the Moon (as long as it’s >60 degrees from target).

As an AP rule of thumb fewer targets have [OIII] and even fewer have [SII].

Shooting through LP and the narrower bandpass means your data will be very faint unless the target is rich in that gas. Since the data will be fainter from the tighter bandpass you’ll need to gather more or longer subs.

Depending on your camera you’ll want to adjust your cameras gain and offset given the fainter data - increase gain to increase your SNR and swamp the noise and increase your offset to bump your signal off the black (left) side of your histogram.

I shoot a QHY268M Pro at Gain 56 and Offset 100 when shooting narrowband. My Antlia filters are all 2” mounted - Ha (3nm), [OIII] (3.5nm), [SII] (3nm). Sub duration is either 180s or 300s depending on target, LP and moon pollution.

Clear Skies and God Bless!

Kip

Nikhil · May 28, 2026 at 08:03 PM

Dave Stirling · May 28, 2026, 03:03 PM

Nikhil · May 28, 2026 at 05:02 AM

Hello all.

With galaxy season coming to a close, I've started a narrowband project for my monochrome camera. With only preliminary data, I noticed a severe problem with my ZWO OIII 7 mm filter. It seems to produce terrible halos around bright stars (I’ve included the images below) and this is apparently a very common problem with this filter. I've upgraded to the Antlia OIII 3 nm filter and I'm waiting for it to arrive.

I wanted to ask experienced people in the community, do you think it's worth it to upgrade my other Ha and SII 7 nm narrowband filters while I'm at it? Those filters don't seem to produce artifacts but I'm mainly asking with regards to the benefit of going to a smaller bandpass.

Thanks very much for your input!

📷 1000012068.jpgfirst image description: HOO image of zeta oph. Very noticable halo around the bright central star.

📷 1000012062.jpgsecond image description: same as first image but only Ha data. No noticeable artifacts.

I think halos are a function of the quality of the filter rather than the bandpass. You would likely see improvement in halos around OIII specifically with the higher quality filter, so it would be interesting to see how much halos diminish by swapping out the OIII with the new filter you’ve ordered first. Highly recommend 3nm for high light pollution (I’m in Bortle 6).

That would make sense that halos depend on filter quality.

Judging from your’s and the previous commenter’s inputs it seems that a 3 nm bandpass won’t make too much of a difference since I am at a dark site.

Thanks for sharing your experience!

I’m envious of your dark site! Looking forward to some posts with the new OIII filter.