Is the Altair 4nm dual-band filter worth it?

It gave me the best-looking raw colour of the three filters on the Veil, but it failed my star-halo test on Sadr and the cheaper SVBONY SV220 won overall. Buy it for colour on star-poor fields; buy the SV220 if bright stars matter.

Does it cause star halos?

Yes, in my test. Around Sadr it threw halos, as the Optolong L-eNhance did; the SVBONY SV220 passed with none.

How does it compare with the SVBONY SV220?

Before noise reduction the Altair showed a little more red in the nebula. After NoiseX and BlurX I leaned towards the 3 nm SV220, which also kept its stars free of halos.

What are its bandpasses?

4 nm at OIII 500.7 nm and 4 nm at Ha 656.3 nm, on 1.85 mm glass in a 2 inch cell with an M48 x 0.75 thread.

Which camera is it for?

A colour camera. I tested it on a colour camera with 30 minutes per target, and it brings nebula detail closer to what a mono camera with separate filters gives.

Does it come with a test report?

Yes. Altair ships each filter with its own high-resolution spectrographic test report.

What have I not tested on the Altair 4nm filter?

I did not measure the bandpass or the transmission myself, and I tested it on one colour camera on one night.

Altair Ha OIII 4nm dual-band filter review: my three-filter 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
4	Altair LRGB	79 out of 100	£240
7	Antlia 2.5nm HSO	75 out of 100	£1,740
8	Altair Ha OIII 4nm	74 out of 100	£399
11	Optolong L-Enhance	61 out of 100	£149
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 How good is it? Here's what I captured
05 What is it for
06 Watch the dual-band comparison
07 Should you buy it?
08 Questions and more about this review

In 30 seconds

Stars for Your Buck 74/100

Reviewed 2 May 2026 Updated 25 Sep 2026

Rank: #8 of 13 filters
Verdict: Worth a look

Written by Damon Scotting 5 min read

Buy it if

You shoot a colour camera and want the strongest nebula colour straight from the stack
You want a filter that ships with its own spectrographic test report
Bright stars rarely sit in your frames

Skip it if

You frame bright stars: it threw halos in my star-halo test on Sadr
You want the best value dual-band filter: the SVBONY SV220 won my test for less
You shoot a mono camera: separate narrowband filters suit it better

“The Altair filter is the most expensive. And as it seems, based on our first test, it's also the filter that produces the best image.”

Specifications and features

Against the filters I have reviewed

Compare with

Altair Ha OIII 4nm reviewed #8 of 13	SVBONY SV220 Ha OIII 3nm #3 of 13	Optolong L-Enhance #11 of 13	Optolong L-Ultimate Dual-Bandpass 3nm #12 of 13
Recorded UK price	£399	£249	£149	£216
Stars for Your Buck	74/100	92/100	61/100	43/100
Type	Dual-band: Ha and OIII in one filter	Dual-band narrowband filter (H-alpha and OIII)	Dual-bandpass light pollution filter (H-alpha, H-beta and OIII)	Dual-band narrowband filter (H-alpha and OIII)
Bandpass	4 nm each band, tolerance about ±0.5	3 nm OIII, 3 nm H-alpha, tolerance ±1	H-alpha 10 nm; OIII + H-beta 24 nm	3 nm OIII, 3 nm H-alpha
Lines passed	OIII 500.7 nm and Ha 656.3 nm	OIII 500.7 nm, H-alpha 656.3 nm	H-alpha, H-beta, OIII	OIII 500.7 nm, H-alpha 656.3 nm
Peak transmission	Ha 90 to 94%, OIII 88 to 91%	85% or more on average (OIII and H-alpha)	Over 90%	90% or more on average
Sizes	2 inch (M48 x 0.75 thread)	2 inch, M48 x 0.75 (the size I used); 1.25 inch also sold	1.25 inch, 2 inch (the size I tested), Canon EOS-C clip-in	1.25 inch (the size I use), 2 inch
Thickness	1.85 mm	2.0 mm substrate	1.85 mm B270 glass	1.85 mm
Coating	SiO2 hard overcoat with UV/IR block and anti-reflection coating	Multi-layer minimal halo coating	Multi-layer anti-reflection, non-cemented, ion-assisted deposition	Multi-layer anti-reflection, non-cemented, ion-assisted deposition
In the box	Filter and its spectrographic test report	2 inch SV220 3 nm filter; plastic case; outer packing box	Protective plastic case with EVA foam lining	Protective plastic case with EVA foam lining

The same target through each filter

The Altair Ha OIII 4nm against three other filters on Western Veil, North America and Sadr, one telescope and one camera, star-aligned

Against

⇔

No filter Altair Ha OIII 4nm Western Veil drag

Western Veil (supernova remnant) · Askar SQA106, ZWO ASI2600MC Pro, ZWO AM3N · Ha and OIII · Bortle 6.8 (in my garden) Left: No filter, 30 min (10 x 180 s) Right: Altair Ha OIII 4nm, 30 min (10 x 180 s)

On the Altair Ha OIII 4nm

“Both it and the SV220 are pretty noisy, but it just seems as though the red of the nebula is popping a little bit more in the Altair image.”

Western Veil Nebula

On the Altair Ha OIII 4nm

“As we can clearly see the Optolong L-eNhance filter fails to pass the dreaded star halo test. So too, in fact, does the Altair 4nm filter ultimately suffering the same fate as the Optolong.”

Sadr, the star-halo test

Western Veil: Askar SQA106, ZWO ASI2600MC Pro, ZWO AM3N, Bortle 6.8 (in my garden); Altair Ha OIII 4nm 30 min (10 x 180 s); SVBONY SV220 Ha OIII 3nm 30 min (10 x 180 s); Optolong L-Enhance 30 min (10 x 180 s); No filter 30 min (10 x 180 s)
North America: Askar SQA106, ZWO ASI2600MC Pro, ZWO AM3N, Bortle 6.8 (in my garden); Altair Ha OIII 4nm 30 min (10 x 180 s); SVBONY SV220 Ha OIII 3nm 30 min (10 x 180 s); Optolong L-Enhance 30 min (10 x 180 s); No filter 30 min (10 x 180 s)
Sadr: Askar SQA106, ZWO ASI2600MC Pro, ZWO AM3N, Bortle 6.8 (in my garden); Altair Ha OIII 4nm 30 min (10 x 180 s); SVBONY SV220 Ha OIII 3nm 30 min (10 x 180 s); Optolong L-Enhance 30 min (10 x 180 s); No filter 30 min (10 x 180 s)

How good is it? Here's what I captured

Three targets

NGC 6960 Western Veil Nebula, ASI2600MC Pro, Altair Ha OIII 4nm

Integration: 30 min (10 x 180 s)
Field: 2.67 x 1.78 degrees
Telescope: Askar SQA106
Camera: ZWO ASI2600MC Pro
Mount: ZWO AM3N
Target: NGC 6960 Western Veil Nebula
Type: Supernova remnant
Location: Bortle 6.8 (in my garden)

NGC 7000 North America Nebula, ASI2600MC Pro, Altair Ha OIII 4nm

Integration: 30 min (10 x 180 s)
Field: 2.65 x 1.76 degrees
Telescope: Askar SQA106
Camera: ZWO ASI2600MC Pro
Mount: ZWO AM3N
Target: NGC 7000 North America Nebula
Type: Emission nebula
Location: Bortle 6.8 (in my garden)

Sadr (Gamma Cygni) and IC 1318, ASI2600MC Pro, Altair Ha OIII 4nm

Integration: 30 min (10 x 180 s)
Field: 2.67 x 1.78 degrees
Telescope: Askar SQA106
Camera: ZWO ASI2600MC Pro
Mount: ZWO AM3N
Target: Sadr (Gamma Cygni) and IC 1318
Type: Bright star in an emission nebula, the halo test
Location: Bortle 6.8 (in my garden)

What is it for

Two things it is for

Narrowband detail from a colour camera

I'm using a colour camera. This is just a single filter. Your images are still going to turn out in colour, but with the help of these filters, you're bringing out similar levels of detail to what the likes of monochrome cameras with specific filters can do.

A faint field turned into nebula

This is perhaps the perfect nebula to demonstrate the importance of a colour filter on. It has made this into a completely different image.

Watch the dual-band comparison

What is the BEST Astro Filter on the Market in 2026? · published 2 May 2026 · 6:06 · Watch on YouTube · 5,706 views, 316 likes on 2 Oct 2026

Jump to

0:29 Three targets and the judging
0:55 The rig: Askar SQA106 and ASI2600MC
1:34 Ten 3-minute subs per filter
2:06 Round one: the Veil Nebula
2:58 Round two: the North America Nebula
3:21 After NoiseX and BlurX
4:07 Round three: the star-halo test
4:34 The halo results
5:21 The final results

Transcript of the video 1,108 words · 10 chapters · searchable

Press a time stamp to play from there.

0:00 The best colour-camera filter?

0:00 Tonight I'm going to answer the question, what is pound-for-pound the best colour camera filter on the market today? 0:05 In this video, we're going to be finding out as I test the SVBONY SV220 filter versus the Optolong L-eNhance filter and the Altair 4nm dual-band filter, as well as of course as no filter at all for a control variable. 0:17 Each of these filters cost very different amounts and as it turns out produce very different results. 0:22 Which one comes out on top? 0:24 Let's find out. 0:24 I'm Damon Scotting and this is Astronomical.

0:29 Three targets and the judging

0:29 Okay, so let's jump straight into this. 0:31 No messing around. 0:31 I'm going to show you three different nebula based deep sky targets tonight. 0:34 And we're going to be looking at for which one provides the most detail, contrast, and least amount of star haloing with their filter. 0:40 I'm also going to be putting each image through various stages of editing so that you can see how your final image will likely turn out. 0:47 So, let's get started with a supernova remnant known as the Veil Nebula. 0:52 In particular, we are looking at the Eastern Veil Nebula.

0:55 The rig: Askar SQA106 and ASI2600MC

0:55 To capture these images, we are using the uber powerful and sharp Askar SQA106 telescope. 1:00 This is a scope that is practically guaranteed to give us the best colour and details we could possibly hope for. 1:06 I'll also be using the ASI 2600MC camera to take 26 megapixel colour images. 1:11 So, that's the key distinction here to note. 1:13 I'm using a colour camera. 1:15 This is just a single filter. 1:15 your images are still going to turn out in colour, but with the help of these filters, you're bringing out similar levels of detail to what the likes of monochrome cameras with specific filters can do, but just, you know, with less mucking around. 1:28 So, to summarize, this is an absolute beast of a setup. 1:30 The conditions tonight are flawless. 1:32 So, let's get started.

1:34 Ten 3-minute subs per filter

1:34 So, for each shot, you are looking at 10 stacked 3-minute images, which means we have 30 minutes of exposure time per shot. 1:40 And a key distinction I'm going to apply to each image is the exact same NoiseX and blur effect. 1:46 effectively improving the sharpness and noise of each image to give an idea of its full potential. 1:49 This isn't so important for our filterless image here, but when it comes to our heavy intense filters, the images tend to be noisier as less light reaches the sensor. 1:59 Now, since the filter I'm mostly focusing on reviewing today is supposed to be the SV220, that will be the final filtered image shown. 2:05 But, as you can see, the Altair filter is the most expensive.

2:06 Round one: the Veil Nebula

2:08 And as it seems, based on our first test, it's also the filter that produces the best image. 2:12 Both it and the SV220 are pretty noisy, but it just seems as though the red of the nebula is popping a little bit more in the Altair image. 2:20 The Optolong L-eNhance image is a nice step up in terms of highlighting the nebulosity in the image, but it still falls miles short of the SVBONY and Altair filters. 2:28 Here's a little insight into the effects of NoiseX and BlurX on our images. 2:56 So yeah, all in all, round one goes to the Altair 4nm dual-band filter.

2:58 Round two: the North America Nebula

2:58 This is the North America Nebula. 3:02 And I mean, look at the upgrade right here. 3:04 That is something special. 3:06 This is perhaps the perfect nebula to demonstrate the importance of a colour filter on. 3:10 It has made this into a completely different image. 3:14 It feels like I'm comparing 10-minute exposures with 10 hours. 3:15 The Altair and SVBONY filters take it a step further and really fine-tune the nebulosity.

3:21 After NoiseX and BlurX

3:21 But again, I feel the Altair filter edges it, or at least I do until you apply NoiseX and BlurX. 3:27 It's worth noting here that the Altair filter is supposedly 4 nm whilst the SVBONY is supposedly 3 nm, meaning it's even more specialized and filters out a lot more light. 3:39 Case in point, when you reduce the noise by the same amount on both, I'm starting to lean towards the SVBONY filter as being the best. 3:44 So maybe we just need some more exposure time to really start to appreciate who the real winner is here. 3:50 With that being said, in terms of testing on the North America Nebula, I don't think there are any losers here. 3:55 Every single one of them improves upon the raw image significantly, although the slight greenish hue the stars are getting in the Altair and SVBONY images is certainly something to keep an eye out for. 4:05 This will require a bit of tweaking in post to correct it, which then leaves us with a final target of the video.

4:07 Round three: the star-halo test

4:12 Deneb the star one third of the Summer Triangle. 4:15 This star is going to be key to determining which filter is ultimately the best. 4:19 Why? 4:19 Because what really separates the men from the boys when it comes to filters is whether or not there are any star halos. 4:24 Basically a deal breaker for most astrophotographers. 4:28 So the question is will they all pass the test? 4:30 Now Deneb is a very bright star making a great target to test this out on.

4:34 The halo results

4:35 As we can clearly see the Optolong L-eNhance filter fails to pass the dreaded star halo test. 4:39 So too, in fact, does the Altair 4nm filter ultimately suffering the same fate as the Optolong. 4:46 This is very upsetting as it likely means all three filters are going to suffer the same fate. 4:51 Except, wait, look at that. 4:51 The SVBONY SV220 filter passes the test with flying colours. 4:58 No star halos to be seen here. 5:01 How crazy is that? 5:01 It feels like it was always going to be very hard to pick a winner between the two here, but this final test makes it clear and obvious which filter produces the higher quality images. 5:10 The SVBONY filter images are still certainly noisier and gives our blue stars an even more greenish hue. 5:16 But it's doing a great job at bringing out the nebulosity whilst also keeping the stars the right shape and with no star haloing.

5:21 The final results

5:22 So, there we go. 5:24 Those are our final results. 5:24 I will leave it up to you in the comments to decide for yourselves which of these filters you think offered the most star for your buck. 5:30 You can find direct links and even discount codes for each of the products featured in today's video by checking out the description down below. 5:38 Leave a comment stating which filters you would like for me to test out next.

Should you buy it?

74/100 Stars for Your Buck

Pros

“All in all, round one goes to the Altair 4nm dual-band filter.”
It pulled clearly more nebulosity than the Optolong L-eNhance on the Veil
Each filter ships with its own spectrographic test report
Published peak transmission of 90 to 94% at Ha and 88 to 91% at OIII

Cons

It threw halos round Sadr in my star-halo test; the SVBONY SV220 did not
After the same noise reduction on the North America Nebula, I leaned towards the cheaper 3 nm SVBONY SV220
Stars took a slight green hue that needs correcting in processing
The most expensive of the three dual-band filters I tested

I feel the Altair filter edges it, or at least I do until you apply NoiseX and BlurX.

Who the Altair 4nm filter is for

Colour camera imager chasing nebula colour

Buy

It gave the strongest red in my Veil frames before any noise reduction.

Imager who frames bright stars

Skip

It threw halos round Sadr; the SVBONY SV220 passed the same test.

Value-first colour imager

Skip

My recommendation is the SVBONY SV220: it won my three-filter test and costs less.

Upgrading from a wide dual-band filter

Buy

It pulled more nebulosity than the Optolong L-eNhance on the Veil and the North America Nebula.

Buyer who wants a documented filter

Buy

Each filter comes with its own spectrographic test report, so you see the bandpass of the one you own.

Mono camera owner

Skip

Separate narrowband filters suit a mono camera; this one is made for colour sensors.

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 Altair Ha OIII 4nm

Reviewed 2 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 Altair 4nm dual-band filter worth it? It gave me the best-looking raw colour of the three filters on the Veil, but it failed my star-halo test on Sadr and the cheaper SVBONY SV220 won overall. Buy it for colour on star-poor fields; buy the SV220 if bright stars matter. The same target through each filter ↓
Does it cause star halos? Yes, in my test. Around Sadr it threw halos, as the Optolong L-eNhance did; the SVBONY SV220 passed with none. The same target through each filter ↓
How does it compare with the SVBONY SV220? Before noise reduction the Altair showed a little more red in the nebula. After NoiseX and BlurX I leaned towards the 3 nm SV220, which also kept its stars free of halos. The same target through each filter ↓
What are its bandpasses? 4 nm at OIII 500.7 nm and 4 nm at Ha 656.3 nm, on 1.85 mm glass in a 2 inch cell with an M48 x 0.75 thread. The specifications and the comparison table ↓
Which camera is it for? A colour camera. I tested it on a colour camera with 30 minutes per target, and it brings nebula detail closer to what a mono camera with separate filters gives. What is it for ↓
Does it come with a test report? Yes. Altair ships each filter with its own high-resolution spectrographic test report. The specifications and the comparison table ↓
What have I not tested on the Altair 4nm filter? I did not measure the bandpass or the transmission myself, and I tested it on one colour camera on one night.