Optolong L-eXtreme Review

The Optolong L-eXtreme Filter

The Optolong L-eXtreme filter is the bigger brother to the hugely popular and widely well received Optolong L-eNhance filter. The L-eXtreme is a duo-narrowband filter that lets through Hydrogen-Alpha and Oxygen-III wavelenghts.

The filter is used best on emission nebula and supernova remnants. I’ve had this filter for a while and used it between a DSLR and a dedicated astronomy camera. In this article I’ll be sharing my thoughts about this narrowband filter that was designed for use mainly with one-shot colour (OSC) cameras.


OSC Suitability

A Small Bayer Pattern Example
A traditional RGGB Bayer Pattern

One issue that narrowband filters have when used with colour cameras is due to the bayer pattern. The bayer pattern – or Colour Filter Array – is a set of coloured filters over the sensor in a tiny square pattern. This tints the incoming light to a specific colour, which then lets the sensor ‘see’ the colour and create an image.


What narrowband filters usually do is isolate a specific colour. For example Hydrogen-Alpha is well up there in the red part of the visibile spectrum. This means the light coming through the filter is only red, which then means the red bayer pattern picks up signal. This reduces the signal to noise ratio and means you really, really need to pile on the integration time.

These multi-bandpass filters compensate for this by allowing multiple wavelengths of light through. Hydrogen-Alpha and Oxygen-III are on the Red and Blue parts of the spectrum, as well as slightly in cyan. This activates all RGB colours on the bayer pattern, resulting in a much better signal to noise ratio.

Optolong L-eXtreme Filter Review

So time to get into the real meat of this review. I got this filter in the summer. Since then I barely got time to use it, and when I did I was using it with a modified Canon 600D in the height of summer. I then invested in a dedicated cooled camera so I’ve been able to use it between both.

The user experience was, as you would expect, rather different. One was more suitable than the other. Before deciding it’s a cut and dry experience let me explain how it went.


I’m going to start with the DSLR experience.


The L-eXtreme With A DSLR


This is how I first received the filter for review. I was using my astro-modified Canon 600D which I was getting success with. I had even used it with 10 minute exposures with a Baader 7nm Hydrogen-Alpha Filter so I felt like the experience was going to be quite similar. My first idea was to use the filter on low hanging fruit. In summer, Cygnus is a great target. So I turned the equipment towards the Eastern Veil Nebula. The Veil nebula are supernova remnants which are full of Ha and OIII data.

Eastern Veil Nebula with the L-eXtreme


Naturally the signal coming through was very crisp. There was a lot of separation of sky to DSO. Considering I’ve previously shot the Western Veil with narrowband filters and a mono camera, it made for some good viewing. I felt the results were relatively comparable. In the image above I have over stretched the photo to highlight an issue I faced. That was with banding, as well as some small halos that can be seen.


I also used the L-eXtreme and the Canon 600D on the Pelican Nebula also. Being an emission nebulae it falls within the catchement and suitability of this filter. I was running 10 minute exposures as I wasn’t seeing much signal with anything less.


The biggest downside I saw with this filter and a DSLR was exactly them sub exposures. I had to use really long exposure times. Unfortunately at the height of summer this isn’t a good thing. My images were really noisy due to heat degradation. Even comparing similar images and exposure times from a Ha filter and this eXtreme filter, the eXtreme filter came off worse.


You can see the result of that first night’s imaging with the video on my YouTube Channel.



Even though I’m reaching a conclusion now with the L-eXtreme and DSLR, I’ll continue testing this if I am able to in the winter to see if it’s any better.




L-Extreme With A Dedicated Camera


Okay so I got myself a ZWO ASI 071mc Pro. When I began using this camera with the L-eXtreme, everything changed!


Cooling the camera and the higher efficiency, teamed with the already high transmission of the filter meant that I felt like I was making the absolute most of the light collected. Also, the cooling just meant that the images were cleaner and more usable. Admittedly I’ve only made one full image with this combination. That was with the Heart Nebula. You can catch the video of it here if you wish.



It was so easy pulling the nebula out from the background sky. Even though my style is to edit the background seperately but it was just straightfoward. Then doing the work on the nebula itself was simple also.


I also took some single shots of targets. These are unbayered so monochrome. But still it’s interesting to see how they turn out. I’m going to keep using this filter for as long as I can, but yeah hugely impressed with this combination.


Heart Nebula single image with the L-eXtreme
Heart Nebula 300 second single RAW image
Single 5 minute shot of the Cave Nebula with the L-eXtreme
300 second single RAW image of the Cave Nebula
Sadr single image with the L-eXtreme
A single 300 second RAW image of the Sadr Region


The L-eXtreme Filter Itself


So how does this filter perform? Well if you’re getting the idea that it’s a pretty good filter, you’ll be correct. It’s like the L-eNhance filter, but more. Narrower bandpass, smaller stars, better seperation.

However in my time with the filter. I have certainly noticed one major, killer difference between the eXtreme and the eNhance.


The dreaded Halos.




So the halos are strange with this filter. Unlike the Altair Triband filter I used, which consistently shown halos around brighter stars, the Optolong L-eNhance didn’t really show any halos, and the L-eXtreme shows halos every now and then.


Sometimes when you think there’ll be halos around brighter stars, there aren’t. Here is a 10 minute exposure of the bright star Navi in Cassiopeia. This is a -4 magnitude star, the centre of the W of Cassiopeia.

10 minute exposure of Navi with the L-eXtreme



So yes. Clean image. No halos. However then I compare it against other images like this single shot of the Cave Nebula you can see a halo. But really are apparent in this single shot of the Sadr region, and especially with the stars below the Veil Nebula



L-eXtreme Halo
Halos near the Veil Nebula


Halos near the Cave Nebula
Halos in the Sadr Region

Seperation Of DSO To Sky


So the main reason we use narrowband filters is to kick the light pollution out, keep the details and make the nebula POP.


And boy does it POP.


Here I’ll show you three images. These were shot in the exact same way; same night, same equipment, same exposure. One after another. The only thing I changed was the filter.


This is a 5 minute image with no filter at all. Not even a UV/IR filter (which was needed). I haven’t edited these photos by the way. They’re raw.



Look, basically no detail. No nebulae.


This is a 5 minute with the IDAS NGS-1 Filter. Some details are beginning to appear but not much.



And here’s the 5 minute image with the L-eXtreme.


Sadr single image with the L-eXtreme


Look at them DETAILS. It’s intense. So amazing. Absolutely mindblowing.


Target Suitability


The Optolong L-eXtreme is a narrowband filter. This sort of limits your target choice. Narrowband filters are very suited for emission nebulae. These are things like the Heart Nebula, Orion Nebula, Horsehead Nebula. In the fantastic program Stellarium, these are referred to as HII Regions. This rules out using the filter for things like galaxies, star clusters and reflection nebulae (like the Pleiades).


If you use this filter properly on HII regions, you’ll be putting this filter to its full potential. You could turn the L-eXtreme to certain galaxies and capture Hydrogen-Alpha from them. But otherwise keep it on emission nebulae to reach the Optolong’s full potential.


Moon Filtration


One thing I noticed with the Optologn L-eNhance filter when I reviewed it was it couldn’t filter out the Moonglow. Probably due to the wider bandpass, and the added in Hydrogen-Beta section let in too much Moonglow. You can see that in this image of the Wizard Nebula.


When I shot this image of the Heart Nebula, it was during a Full Moon period. But when I dive into the data, I can’t see any light or gradients seeping in from the Moon. This was very good news for me. Even looking into the O-III channel. This is a great thing for me. I was very pleased to see this filtration.


Oxygen-III Channel showing no gradients


More testing is required for sure. But for now I’m happy to say Moon filtration is there.


Cost & Sizes


One important factor in any purchase is of course the cost and if you can find a suitable product for you. At the time of writing, the sizes available are 1.25″ and 2″ standard threads. I spoke with a contact from Optolong and they have currently said there’s no intentions to make a clip in filter.


The cost of these filters will run you £179 for the 1.25″, and £239 for the 2″. This is about £30-£60 more than what the L-eNhance originally retailed for (they’ve since been reduced in price). Again, that’s quite pricy for a filter I reckon. But the filter does a lot of work. I think it’s worth the money. Especially if you get it on sale!


Gallery Of L-eXtreme Images

California Nebula with the 071mc Pro & L-eXtreme
Heart Nebula with the 071mc Pro & L-eXtreme
A synthetic Hubble Palette image using the L-eXtreme




































Get the filter 



L-eXtreme or the L-eNhance?


So I’ve already got this question several times. I’m now ready to answer it.


They’re very similar filters. Very. But they are different for sure. The eXtreme only lets through two bandpasses, the eNhance gives three. The exTreme is also narrower. Also as mentioned above the L-eXtreme generates occassional halos, and the L-eNhance lets through Moonglow where the eXtreme doesn’t (that I noticed).


So with all that in mind where would I go? What do I suggest?


Recommendation for DSLR users


If you’re using an older DSLR, or you’re not in particularly bad light pollution. I would suggest you get the Optolong L-eNhance filter. I’ve reviewed that also. That’s because the L-eXtreme is just very narrow and puts a lot of demand on DSLR sensors. When I used my Canon 600D with it, I just kept ending up with bandy, hot noisy messes. Sure it didn’t help being in summer. But I just felt like it set the tone. Also, I can only go on what I know!


You may not have seen that one coming. But I’m not going to recommend a setup I wouldn’t be happy using myself.













Recommendation for Cooled Cameras or Newer DSLRs


If you use a cooled camera, or a really high efficiency camera, then I recommend you consider the Optolong L-eXtreme. If you can live with the seemingly inconsistent halos, and are looking for a filter to go into nebulae season with. Then yes, the L-eXtreme will treat you well.


This isn’t to say the L-eXtreme can’t be used with a DSLR or Mirrorless system. Again as mentioned above. I only can go on what I’ve used. Unless you fancy sending me a nice newer DSLR or Mirrorless system to test with.


Looking at you Canon EOS RA




With everything said. I actually really like the L-eXtreme. Really I do. It’s a great filter that can do some serious WORK. Also, to be fair I haven’t seen many halos. Others have reported them, but they’re not as bad as I’ve seen with other filters.


The pricetag, steep, isn’t as expensive as like the Radian Triad Ultra filter (but that’s a totally different kettle-of-fish). It’s an investment which I do believe will do you well.


I’m really impressed with what Optolong did here. They thought of a product and an audience and they executed a product almost flawlessly. I say almost, purely because of them halos. I don’t like halos, and they’re basically a deal-breaker. But they’re not that bad really.


I hope this review was useful for you and has been a good tool in your buying decision. Thanks for reading.


Clear skies all, keep looking up and keep them cameras clicking.














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