 Multi-bandpass narrowband filters for color cameras are a definite hit in the amateur astrophotography community. Many people are using them to photograph emission nebulae from light polluted cities with color cameras including DSLRs but also dedicated astronomy cameras. Today I'm going to be reviewing three options. Two of them are pretty well established as good budget options. In the two inch format the Optalong L Enhance is $229 USD, the Optalong L Extreme is $309 USD, and the last one is new on the market. It's the Antlia ALP-T and it will retail for $380 USD. So we have sort of a good range here, $229 to $309 to $380 USD, and they're all basically designed to do the same thing which is to isolate the light from emission nebulae, specifically the O3 emission line and the HLFA emission line, and the way that they work is that they pass the light at those specific parts of the visible spectrum, and how much of the light they pass around the emission line is called the band pass, and anything that is not included in those specific band passes is reflected away and blocked from reaching the camera's sensor. So in addition to being great filters for capturing emission nebulae, they also work excellently for blocking light pollution, which is why I'm testing them here just outside of Boston in a Bordel 8 sky with plenty of bright lights all around me from houses and schools and street lamps and businesses. Now I want to make clear upfront what these filters are not good for, which is photographing basically anything other than emission nebulae. So they aren't good at capturing natural star color, they're not designed for capturing reflection nebulae or other galaxies. Now galaxies are sort of a special case because if it's a galaxy that has a lot of emission nebulae like m33 or the Magellanic clouds, then you might be able to get a cool photo using these kinds of filters, but it wouldn't be your typical galaxy photo like this, which is taken with broadband filters, not narrowband. So again their main use case is really for emission nebulae, nebulae that emit their own light from ionized atoms associated with the different gases in the gas clouds like hydrogen, oxygen, and sulfur. And importantly these clouds of gas emit a very specific wavelengths of light that the filters can be designed to pass while blocking all the other light. So what I'm going to do with this video is complete reviews of these three imaging filters, including shootout results, which I'm taking right now, but before I jump in, let me just go through a couple quick disclosures. I was not paid for these reviews. I'm also not given any talking points or anything like that. Anything in this video is coming from me and me alone. However, I didn't pay for these filters. Optalong sent me to LXtreme for the purpose of this review, and Agena Astro, which is a great online store, worked with Antlia and they loaned me the Antlia ALP-T filter a few weeks before it's available for sale here in the States from Agena. And Optalong Ellen Hans, I bought a long time ago, but with proceeds from my Patreon, which is the main financial support for this YouTube channel. So a big thank you to Optalong, Antlia and Agena Astro and my Patreon members. Your support really means the world to me, and it allows videos like this to happen. So let's jump in now, and I'm going to start with the spectral response of these filters. I measured each filter at home. I had put together a spectrometer and a suitable lamp the last time I did filter reviews, and these are the actual measured spectra with my home setup. And you can see from this that all three filters are pretty well centered on the emission lines like they're supposed to be. But the more expensive filters have the tighter band passes as advertised. The Antlia have the five nanometer band passes, the LXtreme has the seven nanometer, and the Ellen Hans has a 24 on the 03 line and a 10 nanometer pass on the HA line. Now something sort of interesting is taking these spectra and plotting them to get transmission curves. Now my setup is not super high resolution, but I still think I get a pretty good idea of how the filters I have stack up against the plots that the manufacturers publish. So I can compare my particular samples to the suggested transmission curve for the filter in general. So starting with the Ellen Hans, I found the full width half maximum, meaning the width of the pass bands was accurate, and they were also well centered. In terms of transmission at the emission lines, my filter looks pretty close, maybe just a few percent lower than the advertised peak transmission. But still in the high 80s, so I think pretty good. With the LXtreme, the 03 was well centered, the HA pass maybe just a tad off, but like I said, it's hard to say at my resolution of my spectrometer. And the peak transmission was in the mid 80s for both lines. So I think just a little bit lower than the published low 90s or 90% that Optalong suggests. The Antlia tested pretty well. The passes were well centered on the emission lines, and they were of the right width of 5 nanometers. The peak transmission for the H-alpha line looked to be above 90%, which was quite impressive. But the transmission on the 03 line was maybe just a tad under the advertised 85%. I think it was closer to 80% for my sample. Turning briefly to physical characteristics, the Ellen Hans gets points for being available in two inch, one and a quarter inch, and a Canon clip-in. It's the only one of these three filters that has the clip-in format available. It comes, the two inch version comes in a semi-clear plastic box with nice foam insert to hold it. The filter cell has minimal knurling on the top and is smooth on the sides. It measured 6.93 millimeters thick when you include the threads and 4.97 millimeters above the filter threads. Taking it apart with a spanner wrench, the glass filter itself measured 45.93 millimeters wide. Moving on to the L-extreme, the only difference is that it's not available as a clip-in filter. But in every other way, it's really just like the Ellen Hans, so I won't bore you with the details there. And finally, the Antlia ALP-T. ALP stands for anti-light pollution, but they also call it the golden filter because the coating on one side makes it appear gold. It comes in a sturdy plastic box with a magnetic cover and a waxed sleeve closed with a security sticker, and that's on the inside of the plastic box. It measures 7.2 millimeters thick with threads and 5.02 millimeters above the threads. The glass filter itself, if you take the filter cell apart, measures 46.46 millimeters wide. So now on to the real-world tests. These were all taken on the same night from my Bortle 8-ish yard in Somerville, Massachusetts, just outside of downtown Boston. There was a waxing gibbous moon out, and so the conditions, you can imagine, this is a very light-polluted sky. And these are all going to be shot at f5.4 with a focal length of 464 millimeters, and the target is the flaming star and tadpoles nebulae in a riga. To start out as a baseline, here is a half hour integration with a stock Canon T7, and here is a half hour with the Optalong L Enhance added in the light path with that still that stock Canon T7. And again, here's a half hour integration with the L Extreme now. And finally, a half hour integration with the Antlia ALPT. Okay, now let's turn to a full spectrum modified Canon 6DD. So, you know, this is a modded DSLR, but it could also stand in for a dedicated astronomy camera, which come already full spectrum. And here's the baseline there with no filter, and again, a bordelate sky with moonlight. And now with the L Enhance added, you can see a big difference. And now a half hour with the L Extreme, and finally the Antlia ALPT. Okay, so now that we have an idea of the shots full size, let's take a look at some side-by-side crops, starting with the Canon T7 and zooming in on the flaming star nebulae. And you can see with a stock camera that the reflection nebulae does come out a bit, even from a bordelate sky with moonlight. So that's pretty interesting. You can also see it, I think, a little bit with the wide band pass of 24 millimeters on the L Enhance, the O3 line. But reflection nebulae aren't really going to come through with the tighter narrowband filters like the L Extreme or the Antlia. And now let's look at that same crop, but with the Canon 60D full spectrum. On this one, you can really see the L Extreme and the Antlia ALPT are pretty neck and neck in terms of contrast and light pollution reduction. And they also have the tighter stars from the tighter band passes. So if you're after that, you can see a difference there. The tadpoles are a bit more interesting for this comparison because there actually is O3 signal in there. And I think all three filters did really well, both with the stock DSLR that you're seeing here and with the full spectrum Canon 60D, you're seeing now. All right, last side-by-side, we can look at the noise from the light pollution and at the bright stars in the field. This is from the middle of the picture. In terms of noise, since the L Enhance lets in more light pollution, you do get a noisier image even with identical integration time because after you subtract out that light pollution, you're still left with some photon noise from the light pollution. The L Extreme and the Antlia ALPT do look well matched in the regard of the lower noise and the higher contrast on the sky. There's only one halo that I see in all the pictures and it's on the bright star with the L Extreme filter. With the brightest star in the field, there is a little faint halo there. I can zoom in on it so you can see it a bit better. But I don't see it on that star with no filter or the L Enhance or the Antlia ALPT. So I think I can conclude L Extreme did cause the halo there. Everything that I've gone over in this video plus more is available in my reviews on my website astrophilters.com. All three reviews are up now and you can also examine the full size images and use this fun slider feature I just added to compare with and without filter. I will try to make these living reviews so if I come across any mistakes or things that need updating I'll update them on the website. So I hope you can check that out if you're interested in any of these great filters and I'd appreciate if you use my affiliate link. Now seeing all of my current members here on my Patreon campaign and if you want to see your name in the credits of future long Nebula Photos videos you can sign up over on patreon.com slash Nebula Photos. And we now have over 500 members so it's a big cool community and there are a bunch of benefits outside of just your name in the credits of long videos. Some of those benefits include I now I did one exclusive video and I'm working on a second exclusive video just for Patreon. There are monthly zoom chats where you can ask questions of me and other people on the chat. There is a discord community which is really cool very vibrant lots of stuff going on there including monthly imaging challenges with prizes a quarterly group imaging project we're all working on the same deep sky object together and patreon also has lots of different communication methods you can direct message me straight through patreon.com you can also do it on discord and so there's a lot of cool ways to connect and really get involved and so if you want to accelerate your learning further after watching some of my videos consider joining over on patreon and starts at just one dollar a month and again the link is patreon.com slash nebula photos till next time this has been nico carver at nebula photos clear skies