Is the ZWO 7nm HSO set worth it?

The images are good: its Ha frames sat level with the Altair 7 nm set in my five-set comparison, half a point behind it in my final scores. The value is not. In my final ranking it was the worst value of the five sets.

How does it compare with the Altair HSO set?

Very closely. On the North America Nebula I thought the Altair edged it; on the Sadr region the ZWO stars were a little smaller and I called it a tie. The Altair set costs less.

Is a 3 nm set better than the ZWO 7 nm?

In my test, yes. The Scorpio 3 nm set showed far more nebulosity with smaller, round stars on the same night, and it costs less than the ZWO set.

Which sizes does ZWO sell?

1.25 inch, 2 inch, 31 mm and 36 mm sets. I own the 1.25 inch and the 2 inch sets; my five-set comparison used the 2 inch Ha filter.

Does it work under a full Moon?

Yes. My five-set comparison was shot under a full Moon, when the sky was about Bortle 9, and every set still pulled the nebula out.

Can I see full colour images from it?

Yes: the Rosette Nebula and the Horsehead region in Ha, SII and OIII, each against its unprocessed stack, and the North America Nebula.

What have I not tested on the ZWO 7nm set?

I did not measure the bandpass or the transmission myself, and my five-set comparison used the Ha filter of each set only.

ZWO 7nm HSO narrowband filter set review: my five-set Ha test

Where does it rank on our leaderboard

Nine of the 13 filters on my board, against price
Rank	Filter	Stars for Your Buck	Recorded UK price
1	Scorpio HSO 3nm	100 out of 100	£448
2	Laida HSO 5nm 1.25″	94 out of 100	£154
3	SVBONY SV220 Ha OIII 3nm	92 out of 100	£249
6	QuarkStar Chromosphere	76 out of 100	£1,149
7	Antlia 2.5nm HSO	75 out of 100	£1,740
8	Altair Ha OIII 4nm	74 out of 100	£399
10	ZWO LRGB	70 out of 100	£332
12	Optolong L-Ultimate Dual-Bandpass 3nm	43 out of 100	£216
13	ZWO HSO 7nm Narrowband	32 out of 100	£734

Contents

01 Where does it rank on our leaderboard
02 Specifications and features
03 The same target through each filter
04 In use
05 How good is it? Here's what I captured
06 Raw against finished
07 What is it for
08 Watch the five-set comparison
09 Should you buy it?
10 Questions and more about this review

In 30 seconds

Stars for Your Buck 32/100

Reviewed 18 May 2026 Updated 25 Sep 2026

Rank: #13 of 13 filters
Verdict: With reservations

Written by Damon Scotting 6 min read

Buy it if

You want ZWO's own filters in 1.25 inch, 2 inch, 31 mm or 36 mm sizes
You shoot a mono camera and want a full Ha, SII and OIII set from one maker
You want 7 nm results and the price matters less to you than the name

Skip it if

You want the most nebulosity for your money: 3 nm sets beat it in my test for less
You shoot a colour camera: a single dual-band filter suits it better
You image from bright city skies and want the strongest light-pollution rejection

“I have found that the ZWO filter set provides the worst value for money. Far and away. Maybe it's just here in the UK, but the cost is surprisingly high.”

Specifications and features

Against the filters I have reviewed

Compare with

ZWO HSO 7nm Narrowband reviewed #13 of 13	Scorpio HSO 3nm #1 of 13	Antlia 2.5nm HSO #7 of 13	Altair HSO 6.5nm/7nm Narrowband #5 of 13	Laida HSO 5nm 1.25″ #2 of 13
Recorded UK price	£734	£448	£1,740	£475	£154
Stars for Your Buck	32/100	100/100	75/100	76/100	94/100
Type	Narrowband set: Ha, SII and OIII filters	Narrowband imaging filters, a set of three	Narrowband imaging filters, a set of three (Ultra series)	Narrowband set: SII, Ha and OIII filters	Narrowband imaging filters, a set of three
Bandpass	7 nm each, tolerance ±0.5	3 nm	2.5 nm FWHM (+0.3/-0.1 nm)	Ha 7 nm; SII and OIII 6.5 nm	5 nm FWHM
Lines passed	Ha 656 nm, SII 672 nm, OIII 500 nm	Ha, SII, OIII	Ha 656.3 nm, SII 671.6 and 673.1 nm, OIII 500.7 nm	Ha, SII and OIII	Ha, SII, OIII
Peak transmission	About 90% at each line	not recorded	95% or more (Ha, SII); 92% or more (OIII)	not recorded	not recorded
Sizes	1.25 inch, 2 inch, 31 mm and 36 mm	2 inch mounted, D50 (mine); a 36 mm set is also listed	2 inch mounted, M48 x 0.75 (mine); 36 mm unmounted also sold	2 inch	1.25 inch (mine, model DA1100); a 2 inch set is also listed
Thickness	2.0 mm (1.25 inch, 31 mm and 36 mm)	not recorded	2 mm (+/- 0.05 mm)	1 mm BK7 glass	not recorded
Coating	IR cut from 700 to 1,100 nm; off-band OD3	not recorded	Quartz glass coated to the edge; OD5 out-of-band blocking	UV/IR blocking and anti-reflection coatings	not recorded
In the box	Ha, SII and OIII filters	Ha, SII and OIII filters, each in its own case	Ha, SII and OIII filters, each with its measured transmission and blocking data	SII, Ha and OIII filters, each in a sealed case	Ha, SII and OIII filters, each in its own box

The same target through each filter

The ZWO HSO 7nm Narrowband against four other filters on North America and Sadr, one telescope and one camera, star-aligned

Against

⇔

Laida HSO 5nm 1.25″ ZWO HSO 7nm Narrowband North America drag

North America (emission nebula) · Askar SQA106, ZWO ASI2600MM Pro, ZWO AM3N · Ha only · Bortle 6.8 (in my garden) Left: Laida HSO 5nm 1.25″, 15 min (5 x 180 s) Right: ZWO HSO 7nm Narrowband, 15 min (5 x 180 s)

On the ZWO HSO 7nm Narrowband

“I think that it just got a little worse than the Altair filter.”

North America Nebula, against the Altair

On the ZWO HSO 7nm Narrowband

“I think the ZWO stars are a tad smaller, which is nicer. The filter clearly keeps them tight. But as for the nebulosity and level of noise, yeah, now I'm not sure. Maybe ZWO gets it. Let's just call it a tie between them on this one.”

Sadr, against the Altair

Read my review of the Laida HSO 5nm 1.25″

North America: Askar SQA106, ZWO ASI2600MM Pro, ZWO AM3N, Bortle 6.8 (in my garden); ZWO HSO 7nm Narrowband 15 min (5 x 180 s); Altair HSO 6.5nm/7nm Narrowband 15 min (5 x 180 s); Antlia 2.5nm HSO 15 min (5 x 180 s); Scorpio HSO 3nm 15 min (5 x 180 s); Laida HSO 5nm 1.25″ 15 min (5 x 180 s)
Sadr: Askar SQA106, ZWO ASI2600MM Pro, ZWO AM3N, Bortle 6.8 (in my garden); ZWO HSO 7nm Narrowband 15 min (5 x 180 s); Altair HSO 6.5nm/7nm Narrowband 15 min (5 x 180 s); Antlia 2.5nm HSO 15 min (5 x 180 s); Scorpio HSO 3nm 15 min (5 x 180 s); Laida HSO 5nm 1.25″ 15 min (5 x 180 s)

In use

How good is it? Here's what I captured

Three targets

NGC 2237 Rosette Nebula, ASI2600MM Pro, ZWO 7nm Ha, SII and OIII

Integration: 45 min (15 x 180 s: H 5, S 5, O 5)
Field: 2.18 x 1.46 degrees
Telescope: Askar SQA130
Camera: ZWO ASI2600MM Pro
Mount: Unknown
Target: NGC 2237 Rosette Nebula
Type: Emission nebula
Location: Bortle 6.8 (in my garden)

IC 434 Horsehead and NGC 2024 Flame Nebulae, ASI2600MM Pro, ZWO 7nm Ha, SII and OIII

Integration: 27 min (9 x 180 s: H 3, S 3, O 3)
Field: 2.18 x 1.46 degrees
Telescope: Askar SQA130
Camera: ZWO ASI2600MM Pro
Mount: Unknown
Target: IC 434 Horsehead and NGC 2024 Flame Nebulae
Type: Emission and dark nebulae
Location: Bortle 6.8 (in my garden)

NGC 7000 North America Nebula, ASI2600MM Pro, ZWO 7nm Ha, SII and OIII

Integration: Unknown
Field: Unknown
Telescope: Askar SQA106
Camera: ZWO ASI2600MM Pro
Mount: Unknown
Target: NGC 7000 North America Nebula
Type: Emission nebula

Raw against finished

What is it for

The 2 targets, the raw combined stack against my finished image, each with its integration, the camera and the palette:

NGC 2237 Rosette Nebula: 45 min (15 x 180 s: H 5, S 5, O 5) of light, ASI2600MM Pro, ZWO 7nm Ha, SII and OIII, the raw combined stack with one automatic stretch
IC 434 Horsehead and NGC 2024 Flame Nebulae: 27 min (9 x 180 s: H 3, S 3, O 3) of light, ASI2600MM Pro, ZWO 7nm Ha, SII and OIII, the raw combined stack with one automatic stretch

Two things it is for

Imaging through a full Moon

Narrowband imaging works exceptionally well during a full moon because it captures only very specific wavelengths like hydrogen alpha, sulphur II and oxygen III, blocking most of the broadband moonlight and sky glow that would otherwise wash out the image.

Colour from three channels

We need the full set of filter images to give ourselves a full colour picture.

Watch the five-set comparison

£58 vs £1369 Filters, Can You Tell the Difference? · published 18 May 2026 · 16:23 · Watch on YouTube · 14,155 views, 497 likes on 2 Oct 2026

Jump to

0:51 Why narrowband works during a full moon
2:04 ZWO 7nm £734
2:55 The test rig, SQA106 + 2600MM + 2 inch wheel
3:36 North America Nebula reference image
5:23 ZWO joins the fight
7:35 Switching to Sadr
11:35 Final ranked results table
13:33 Worst value, ZWO

Transcript of the video 2,884 words · 23 chapters · searchable

Press a time stamp to play from there.

0:00 The £19 vs £434 filter question

0:00 Presenting the ultimate filter comparison video. 0:02 Tonight we're going to compare the images captured through a very mixed bag of filters, including a £19 5nm off-brand filter versus a £434 2.5 nm Antlia filter. 0:13 I say this not with the intention to clickbait, but the results here will really surprise you. 0:20 So, let's see which filter will come out on top. 0:22 I'm Damon Scotting and this is Astronomical.

0:25 Tonight's sky, full moon Bortle 9

0:28 It is a gorgeous night here in the middle of England. 0:29 It is a full moon, which means the Bortle has jumped from a pleasant 6.8 to a 9. 0:33 It's a kind of night where imaging in broadband can be virtually impossible. 0:38 The powerful reflected light from the moon washes away most deep sky objects. 0:41 But there is a secret to success when it comes to astrophotography during a full moon, and that involves using narrowband filters. 0:50 Narrowband imaging works exceptionally well during a full moon because it captures only very specific wavelengths like hydrogen alpha, sulphur II, and oxygen III, blocking most of the broadband moonlight and sky glow that would otherwise wash out the image.

0:51 Why narrowband works during a full moon

1:02 So it might not look like it, but tonight is the perfect night to test out the hydrogen alpha filters for all five of these filter companies. 1:10 So without further ado, let's meet today's competition. 1:13 On the extreme budget side of things, today we have the Laida filter set.

1:14 Meet the contestants, Laida £58

1:23 Astrophotography is many things, but affordable isn't one of them. 1:24 So, treat these like the holy grail. 1:26 Most popular affordable filter sets tend to be around the 7 nm range in terms of their bandwidth, but this filter set claims an impressive 5 nm. 1:34 Hm, this really does seem like the definition of too good to be true. 1:39 To the right of them, we have the first naraban filters I ever owned.

1:43 Altair 7nm £475

1:43 These are the Altair HSO filter set coming in at a respectable cost of £475 for the 2 inch set. 1:49 That might seem like a significant jump considering we just explored a £58 set, but I promise you these 2 inch filters are the most affordable industry-leading filters on the market. 2:00 Speaking of which, next up we have perhaps the most popular narrowband set on the market. 2:03 The ZWO filters retail for £734 here in the UK and have very similar specifications to the Altair set.

2:04 ZWO 7nm £734

2:11 We could almost treat these filters as our general benchmark. 2:15 Then we have another off-brand set which promises some big results at some frankly shocking prices.

2:21 Scorpio 3nm £379

2:22 And at 3 nm, they are almost the most powerful filters in this video. 2:27 I say almost because leading the charge, we have the epitome of no expense spared astrophotography gear.

2:32 Antlia 2.5nm, the premium tier

2:33 These are the Antlia 2.5 nm HSO filters. 2:35 And it really doesn't get much better than this. 2:40 As a set, they cost more than most entire astrophotography rigs, which is crazy to say. 2:44 But if they promise us almost three times the results of filter sets half their price, then I think we can agree that they are a bargain. 2:51 Now, in order to make this a fair test, I'm actually going to be taking the hydrogen alpha filters from each of the sets and placing them into my 2 inch filter wheel.

2:55 The test rig, SQA106 + 2600MM + 2 inch wheel

3:00 I'll be using the incredibly sharp Askar SQA106 telescope as our imaging scope and the rather large ASI2600 monochrome as our imaging camera. 3:07 So, this is a very powerful setup. 3:09 But perhaps the first thing you will note is that the bargain bin Laida filter set is at a disadvantage since it's only 1.25 inch. 3:17 Now, there are 2 inch versions of this filter available out there that would have been better suited for this test. 3:22 But, as you will shortly see, the Laida 1.25 inch filters still managed just fine, which is really weird. 3:27 So, I've made another video on this I'll be posting in the near future. 3:30 Okay, let's start imaging so that we can determine once and for all what is the best value filter set in the world. 3:35 So, here is a normal colour photo of the North America Nebula.

3:36 North America Nebula reference image

3:39 This is an hour's worth of stacked images. 3:42 Now, here are 15-minute stacked images of the same deep sky object imaged with their hydrogen alpha filters. 3:48 Obviously, we need the full set of filter images to give ourselves a full colour picture like this one here that I captured the North America Nebula with the Laida 1.25 inch filters the other night. 3:57 But to capture full colour images with each of these filter sets in the same night is basically impossible for me to do. 4:02 And I don't want there to be any variance in these tests. 4:05 I ideally want to be conducting them under the same conditions. 4:07 So, I'm going to stick to just hydrogen alpha images. 4:10 And straight away, boom, kiss of death when it comes to filters. 4:13 Star haloing.

4:14 Laida Ha first impressions, star halos

4:15 And perhaps even more worrying is that the haloing is offcentered. 4:18 Now, this will of course be a result of the smaller filter than sensor size. 4:22 So, it's not worth looking too much into this other than, hey, that's actually a surprisingly decent image from a 19 pound filter. 4:30 You can of course see some slight vignetting in the corners, but if you focus on the central part of the image, it is nice and sharp. 4:35 And now, as a means of comparison, here is the Altair 7 nm filter, which is a clear and obvious upgrade on the corners. 4:43 But I tell you what, if you crop in a bit, that's a surprisingly small improvement, isn't it? 4:48 I was expecting night and day between these filters, but this has really shocked me.

4:50 Altair vs Laida side by side

4:52 And as for the ZWO 2 inch hydrogen alpha filter, I I don't know. 4:55 I think that it just got a little worse than the Altair filter. 5:00 What do you think? 5:00 Let me keep switching quickly between the two here. 5:04 Like I said, these two filters have very similar specs, but very different prices with the ZWO filter price significantly more. 5:10 Let's now do a comparison with the Laida 1.25 inch filter involved as well. 5:15 But now put the ZWO filter in the middle. 5:17 Yeah, how about that? 5:17 What do you think? 5:19 Who is the winner out of these three filters? 5:21 It is a tricky one, isn't it?

5:23 ZWO joins the fight

5:23 It'd be interesting to get an astrophotographer to blind rank all of these images to determine which one they think is the best. 5:29 They have all been stacked in the same way for the record. 5:32 They were then star aligned to make these comparisons easier on the eye. 5:34 But now here's where things really start to get interesting. 5:38 We've seen some unique results from our budget friendly Laida filters.

5:42 Scorpio 3nm, the surprise

5:42 But how is the Scorpio 3 nm filter set going to fare? 5:45 It is cheaper than both of the Altair and ZWO sets and advertises 3 nm compared to their seven making it on paper at least a lot more powerful. 5:55 And based on these images, yeah, I'd back that statement. 5:59 Look how much more the Nebulosity stands out in its image. 6:01 The stars are smaller and still nice and round, but it almost looks like we're comparing a single 3minute long exposure versus 2 hours. 6:06 It is a drastic improvement upon the ZWO filter. 6:13 And by far the most impressive quality is that unlike its cheap 5 nm cousin, it does not produce any star haloing, which is a huge win. 6:19 That is a huge positive for the Scorpio filter set. 6:23 Almost half the price of the ZWO set and yet somehow more than twice as good. 6:27 But is it enough to take down the top tier filter on the market? 6:32 2.5 nm is absurdly fine. 6:32 You can basically forget about any concerns you have about light pollution when using these filters.

6:33 Antlia 2.5nm, the champion?

6:39 They are going to make your Bortle 9 garden feel like it's a Bortle 3. 6:43 What are we thinking here? 6:46 I think we might have to take a deeper look in order to see how this compares versus the Scorpio set. 6:50 Which do you prefer out of the two? 6:52 Because personally, I'm not sure. 6:54 I really am on the fence here. 6:56 I think we're kind of only seeing half the picture here because without a final colour image, there's still a few factors we can't quite consider. 7:02 But this right here is supposed to be black and white. 7:04 It should be clear who the winner is. 7:06 And yet I'm seeing very little variance between these two filter sets. 7:09 So let's try something else.

7:11 Antlia vs Scorpio, neck and neck

7:12 How does the Antlia filter compare versus the Laida? 7:14 It destroys it. 7:16 What about the ZWO? 7:16 It annihilates it. 7:18 And the Altair, it's just all too easy. 7:20 But as for the Scorpio filter set, that generally seems to be neck and neck to me. 7:24 The only way to know for certain who the real winner is is to point my telescope at another target. 7:30 So let's go for a bright star surrounded by thick dust and gas. 7:32 Now my telescope is pointing at the star Sadr.

7:35 Switching to Sadr

7:37 But here's the catch that I'm going to elaborate on in another video. 7:38 You see those corners, but you can actually mostly fix them with a few flats taken. 7:44 It completely smooths out the image. 7:44 And as a sneak peek for the future video that I'm going to be releasing using these filters with the same setup, here are some shots that I captured. 7:51 Each target was between 45 to 90 minutes worth of stacked images. 7:55 If you're not already, make sure you're subscribed to see that video in the near future. 7:58 So, you can actually polish this turd to look relatively impressive. 8:02 The one aspect you can't naturally fix though is the star haloing, which is loud and obvious in this image.

8:04 Fixing halos with StarXTerminator

8:09 But to tell you the truth, when editing the images I captured with it in my next video, I used a StarXTerminator tool to split the nebula and stars. 8:17 I then just blended the star halo out of the image, and you couldn't even tell it was there to begin with. 8:22 Does this extra little bit of work required validate the obscenely low price of this filter set? 8:29 Because as we can see when compared with the Altair 7nm filters, there isn't exactly a stark difference between them. 8:35 Or maybe it is a bit more noticeable when you zoom in 500%. 8:37 The Laida filter images do seem a tad noisier. 8:40 When it comes to comparing the 7nm hydrogen alpha filters of the Altair and ZWO sets, I dare say that the Altair filter just edges it here. 8:49 I think again it's probably too close to say. 8:51 Maybe if we zoom in again 500%, it will make it a little bit easier. 8:56 Yeah. 8:56 So, I think the ZWO stars are a tad smaller, which is nicer. 9:00 The filter clearly keeps them tight. 9:02 But as for the nebulosity and level of noise, yeah, now now I'm not sure. 9:06 Maybe ZWO gets it. 9:06 Let's just call it a tie between them on this one. 9:08 The Scorpio filter has even smaller and tighter stars while still making the nebulosity feel abundant. 9:14 That is a clear and obvious improvement over both of the 7nm filters. 9:19 I really do like this shot a lot. 9:21 which then only leaves us with the 2 and a half nanometre Antlia hydrogen alpha filter. 9:25 And look at that, we've got a very similar scenario here to the two 7nm filters where it's practically neck and neck with the Scorpio filters. 9:33 There are very little variations between these two images. 9:36 But I don't know if it is because the Antlia is next in line for the comparison. 9:41 So it feels like naturally it should progress and be better. 9:42 But my heart is leaning towards the Antlia image being the best here out of the bunch. 9:48 Let me do a few sudden switches between the two filters without their names being shown. 9:52 So, the point we are now at is, do you honestly think that one of these filters is significantly better than the other? 9:58 The entire Scorpio 2 inch 3nm filter set costs less than a single Antlia filter. 10:02 I'm basing this off their prices on AliExpress, by the way. 10:07 If you tried to buy the Antlia filters from a local UK retailer, then they become even more expensive. 10:10 I know it actually means very little since it does not affect the performance in the slightest, but the Antlia filters do look the most premium by far. 10:18 This golden design and detailed labeling makes them feel so much more premium. 10:24 And without the ability to compare them versus other filters directly under the same imaging conditions with precisely the same gear, I think I would have unanimously decided that the Antlia filters were in fact the best. 10:34 Yeah, I think the best way to answer which filter produces the best results would be to ask users to blind rank them. 10:39 So, if you have an astrophotographer friend or just a friend actually, any one will do, give them no previous context and ask them to pick their favourite image from the bunch. 10:50 To make it harder to obviously discern them all, I've cropped it by 25%, changed the order in which they appear, and flipped all of them. 10:55 So feel free to try and blind rank them for yourself. 11:25 So how did you do? 11:25 which filter came out on top. 11:27 These are the correct names of each filter. 11:28 And here they are sorted by the price for each full set. 11:30 Personally, when it comes down to price and the quality of image produced by each filter, this is how I have ranked them.

11:35 Final ranked results table

11:37 In terms of price, I think it's fair to say that the Antlia filters are by far the worst, costing well over £1,000. 11:40 And yet, given how much everything costs in astrophotography, I wouldn't say the prices are extortionate. 11:47 They are probably exactly what you should be expecting to pay for 2 and a half nanometre filters, especially when one of the biggest brands in the world still sells their 7 nm filters for a little under £1,000. 11:58 The Altair filters provided very different results. 12:00 They list very similar specs and cost a lot less than ZWO, but overall they actually only cost a little bit more than the 3nm Scorpio filters I found on AliExpress. 12:09 I would say that these are without a doubt the greatest value filters in the world if it wasn't for the fact that our final contender seems to defy the laws of astrophotography retail. 12:20 The Laida filters are 1.25 inch which does mean they are smaller than the others. 12:24 But even if you buy the 2 inch versions of them, the price is still shockingly cheap. 12:28 Hence why they score a 10 out of 10 in terms of cost. 12:32 Speaking of which, when it comes to scoring the imaging quality, the Antlia filters are indeed top drawer. 12:39 No filters outperform them. 12:39 They walk the walk, earning an impressive 10 out of 10. 12:44 Meanwhile, the ZWO filters, I'm afraid, scored just a tad less than the Altair filters. 12:48 Literally just half a point. 12:51 It was the North America Nebula image that swayed my final decision on this one. 12:54 Both filters provide you with great results and are welcome additions to the narrowband imaging world. 12:58 For the Scorpio images, I think I might be being a little too harsh here and showing a bit of favoritism to the Antlia filters, but I've given them the edge here and scored the Scorpio set 9 out of 10, even though for the most part their two sets of images feel inseparable. 13:12 And lastly, the Laida filters put up a good fight. 13:15 I won't be scoring them harshly on the corner vignetting since they are just 1.25 inch filters, but the star haloing and the general noisiness make this our lowest rated images of the set. 13:25 And with that being said, in conclusion of my test for what is the greatest astrophotography filter set, I have found that the ZWO filter set provides the worst value for money.

13:33 Worst value, ZWO

13:36 Far and away. 13:38 Maybe it's just here in the UK, but the cost is surprisingly high. 13:40 Then for the third place, we actually have a tie between the Laida filters and the Altair.

13:42 Third place tie, Laida + Altair

13:46 Both providing a lot of star for your buck. 13:49 I think the Laida is a must-have as a cheap handy set. 13:51 But the Altair filter set is certainly the most affordable and effective set on the market right now.

13:57 Second place, Antlia

13:57 Its prices are significantly better than the competition. 14:01 In second place, and not by much, are the Antlia filters. 14:03 Premium images also mean premium prices in this case. 14:08 If you want the suffocating light pollution in your area to be an afterthought, then these filters are an excellent choice. 14:14 But in terms of value for money and quality of images, the undisputed champion by a landslide are the Scorpio 2 inch 3 nm narrowband filters.

14:18 Undisputed champion

14:23 They tick every box for me and I've been using them every single night now for the last few months. 14:27 They feel like the most minor of downgrades from the luxury Antlia filters.

Check out more videos on the ZWO HSO 7nm Narrowband

I Bought £58 Astrophotography Filters, Here's What Happened

19 May 2026

Should you buy it?

32/100 Stars for Your Buck

Pros

Small, tight stars: on the Sadr region its stars were a touch smaller than the Altair set's
“Both filters provide you with great results and are welcome additions to the narrowband imaging world.”
Sold as a set in 1.25 inch, 2 inch, 31 mm and 36 mm sizes
About 90% peak transmission at each line, with IR blocked from 700 to 1,100 nm

Cons

It costs far more than the Altair 7 nm set, whose Ha frames matched it in my test
On the North America Nebula I rated its Ha frame a little behind the Altair set's
The Scorpio 3 nm and Antlia 2.5 nm sets both showed clearly more nebulosity than this set on the same night
A 7 nm bandpass is wider than the 3 nm and 2.5 nm sets that beat it

Meanwhile, the ZWO filters, I'm afraid, scored just a tad less than the Altair filters. Literally just half a point.

Who the ZWO 7nm set is for

Value-first narrowband buyer

Skip

My recommendation is the Scorpio 3 nm set: it showed more nebulosity than the ZWO set on the same night and costs less.

Owner of the ZWO set

Skip

Keep it rather than trade sideways: its Ha frames sat level with the Altair 7 nm set, and only a 3 nm or narrower set is a real step up.

ZWO wheel owner who wants 31 mm or 36 mm filters

Buy

ZWO sells this set in 31 mm and 36 mm as well as 1.25 and 2 inch, so it fits a wheel built for those sizes.

Beginner with a small mono sensor

Skip

The Laida 1.25 inch set costs a fraction of this and kept up surprisingly well in my test.

Colour camera owner

Skip

A single dual-band filter such as the SVBONY SV220 suits a colour camera; this set is made for a mono camera and a filter wheel.

Imager under a bright Moon

Buy

Any of these narrowband sets turns a full-Moon night into a working night, and this one gives clean, tight stars.

Three alternatives I have reviewed

Questions and more about this review

Reviewed by

Damon Scotting

The Telescope Man Verified

BSc (Hons) Physics with Astrophysics and Cosmology, Loughborough University PGCE / QTS, University of Nottingham

About Damon About Damon Damon Scotting is The Telescope Man. He holds a BSc (Hons) in Physics with Astrophysics and Cosmology from Loughborough University and a PGCE with QTS from the University of Nottingham, and taught physics in secondary schools before becoming an astronomy creator. He is a contributing writer for BBC Sky at Night Magazine and the author of 42 Wonders of Our Night Sky, and his photograph of the galaxy M100 with the dwarf planet Ceres was Highly Commended in the Astronomy Photographer of the Year 2024 competition run by Royal Observatory Greenwich. He has appeared on the BBC's Blue Peter. More than 750,000 people follow his astronomy channels on YouTube, Instagram and TikTok, and he has reviewed more than 140 telescopes, mounts, cameras, filters and accessories hands-on for this site. More about Damon · How I test · Damon's book

I review all kinds of gear: most of it I buy, some is gifted and some is loaned, and all of it is reviewed the same way. How this site is funded

Seven questions, answered

Questions about the ZWO HSO 7nm Narrowband

Reviewed 18 May 2026 ·Updated 25 September 2026

I review all kinds of gear. Most of it I buy, some is gifted and some is loaned, and all of it is reviewed the same way: no company sees or approves a review before it is published. Shop links marked Ad are affiliate links: I earn a commission when you buy through them, at no extra cost to you. How this site is funded

Is the ZWO 7nm HSO set worth it? The images are good: its Ha frames sat level with the Altair 7 nm set in my five-set comparison, half a point behind it in my final scores. The value is not. In my final ranking it was the worst value of the five sets. The same target through each filter ↓
How does it compare with the Altair HSO set? Very closely. On the North America Nebula I thought the Altair edged it; on the Sadr region the ZWO stars were a little smaller and I called it a tie. The Altair set costs less. The same target through each filter ↓
Is a 3 nm set better than the ZWO 7 nm? In my test, yes. The Scorpio 3 nm set showed far more nebulosity with smaller, round stars on the same night, and it costs less than the ZWO set. The same target through each filter ↓
Which sizes does ZWO sell? 1.25 inch, 2 inch, 31 mm and 36 mm sets. I own the 1.25 inch and the 2 inch sets; my five-set comparison used the 2 inch Ha filter. The specifications and the comparison table ↓
Does it work under a full Moon? Yes. My five-set comparison was shot under a full Moon, when the sky was about Bortle 9, and every set still pulled the nebula out. The same target through each filter ↓
Can I see full colour images from it? Yes: the Rosette Nebula and the Horsehead region in Ha, SII and OIII, each against its unprocessed stack, and the North America Nebula. What I captured ↓
What have I not tested on the ZWO 7nm set? I did not measure the bandpass or the transmission myself, and my five-set comparison used the Ha filter of each set only.