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Thanks for the update Jacob. They should indeed send individual spectrum measurements, not everyone has access to a spectrometer. Arun H: I'm quite curious about that too. |
3.21
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Arun H: I actually did do the remote control test with the new filter and it also showed high NIR transmission. But because the filters use interference (series of metal oxide layers) to cancel out off-band light, the angle of incidence is important so a point source of light like the remote control won't be a good representation unless I can focus it in a bit. Antlia has the old filter now anyway. Certainly the narrower you go, the tighter the tolerances when depositing the metal oxide layers. The UV-Vis instrument at work can measure with a width of 0.1nm from 190-1100nm. Just a shame there's no way of hooking up my filters to it. Let me know when you find your spec sheet. |
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Kay Ogetay: Ideally that would be nice. I guess it also depends on how much variability there is between batches vs individual filters within a batch. If a given batch produces consistent results then you could probably get away with testing a selection. In which case, provide a spec sheet on a per batch basis. |
14.24
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Jacob Heppell: I was able to find the one for my OIII filter and I imagine the others are similar. It goes from 300 to 1150 nm and is specific to my filter. Peak %T is around 97%. |
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Arun H:Jacob Heppell: Nice!!! That's what I like to hear. How does Chroma compete these days when the equivalent Antlia filter is about a third the price for something that I "guesstimate" is at least 90% as good. |
11.18
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So, this is a bit tangential to the topic, but…is anyone noticing any real benefits from filters narrower than 3nm? Are the 2.8nm, 2.5nm filters actually providing some useful improvements in contrast?
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Jacob Heppell: It is a good question. I think a lot of the fixed cost of Chroma filters is paid for through their other businesses, selling into the scientific market. I was around, though not directly involved, when Chroma fist came out with their filters. They got active feedback from customers for their first filters they sent out - that's how they came up, I think, with the cutoff of ranges, optimized their coatings, etc., all with active customer involvement. They also replaced defective filters without question. In my case, I had a reflection issue with my OIII filters that I discovered 3 years in - replaced no questions asked. So all that comes with a cost. At some point, if people don't value that, they'll stop offering astronomical filters, which I wouldn't be surprised if that happens soon. |
3.31
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Jon Rista: I did intensive testing with Antlia OIII 2.8nm ultra, OIII 3.0 nm pro and Astronomik 6nm in 2023 after noticing strange phenomena on IR stars with the newly purchased 2.8nm ultra. I live under a Bortle 4.5 sky. For the tests I had the filters side by side in an EFW 7x36mm on an ASI2600mm pro. First I compared the 2.8nm ultra with the 6nm Astronomik. For the test, I took 8 shots with each filter in turn. The Antlia showed significantly more contrast than the 6nm Astronimik, but it had problems with IR stars (MIRA stars and LPV stars) at more than 30 positions of the test image. Here a cropped gif that shows the better performance of the 2.8nm in the nebula but also atrifacts on 2 IR stars at the bottom and the left side:  My dealer sent me an Antlia 3nm pro for testing. In a side by side comparison with the 2.8 ultra, I couldn't see any significant differences. Only in extremely faint nebula areas did the 2.8nm seem to show minimal, but hardly recognizably better structures, even when stretched strongly. That's why I would have liked to keep it. However, because of the problems with the IR stars, I decided to go for the 3.0 pro in the end. My dealer contacted Antlia at that time but they did not offer a replacement nor a useful explanation .  |
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3.21
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Jon Rista: From what I can tell, the 2.8nm are like the 3nm but with slightly higher transmission and a squarer transmission curve (flatter at the top). To be honest the 2.8nm really should be advertised as 3nm as the advertised tolerance for the 2.8nm is +0.5nm -0.1nm. Might as well just say 3.0nm ± 0.3. Similarly, the 2.5nm +0.3nm -0.1nm could just be stated as 2.6nm ± 0.2nm. Anyway, I went for the 2.5nm more for the flat-top transmission profile that means the filter has a higher maximum transmission for a given amount of red/blue shifting but of course drops off much quicker than the 3nm pro version. Plus I live in Bortle 7/8 so a little less light pollution is a bonus. |
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Arun H: Some good insights there. Sounds like customer service was top notch. I guess we'll see if Chroma stays in the astro filter market. I've lost count of how many of my fellow astrophotographers have bought Antlia's. |
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3.21
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Jon Rista: Don't suppose you ever got a replacement 2.8nm OIII to compare with the defective one? |
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3.31
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Jacob Heppell:Jon Rista: I had expected that Antlia would offer to replace the 2.8nm against a "regular" one. After my dealer sent them my test images and analysis, this is was the only answer from Antlia:  |
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3.21
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I had expected that Antlia would offer to replace the 2.8nm a "regular" one. After my dealer sent them my test images and analysis, this is was the only answer from Antlia: Yeah that doesn't help the cause that much. Certainly for our purposes, OD4 will suffice. Initially I went through the dealer (Agena Astro), who then contacted Antlia. Agena said that Antlia will likely contact me but, after hearing nothing for about a week, I contacted Antlia directly. I showed them the test images and they agreed there was a problem plus I suggested they test out to 1100nm, which they said they did. They agreed to replace the filter after they did the test out to 1150nm, which took weeks but got there eventually. |
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Jacob Heppell:Arun H:Jacob Heppell: This is exactly how Chroma competes from my point of view. A customer service that doesn't say "there is no problem with our filters go check it out yourself if you don't believe" when there are IR stars appearing on your image out of blue. You either pay extra for professional customer support or you gamble with your cheaper option. I have seen a lot of people's different complaints on the cheaper option, but almost never with the other. Still, I have to criticize, I find Chroma too expensive for the purpose. Not even talking about working conditions that we support. |
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Kay Ogetay: I have mixed feelings about all this. On the one hand, it is good that cheaper options are available since more people can then access the hobby. On the other hand, there is no question that all this is undercutting manufacturing of critical goods in the US and Europe. We (and here I include myself, since I have bought ZWO cameras, filter wheels, etc. in preference to more expensive options) insist on good working conditions and living wages in the US and Europe, but then also buy all manner of things made under conditions that do not meet the standards we insist on for our own manufacturing. In the end, I think we will come to regret the loss of these very critical industries and skills in the west. |
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3.21
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Kay Ogetay: Yep fair enough. I certainly considered the options before going to Antlia. The trade off with the cheaper option is probably worth it for most of us. This hobby is expensive enough as it is really without having to fork out ~$2k AUD for one NB filter, which was completely unjustifiable for me. Although, filters are a "buy once, cry once" sort of thing. They should last virtually forever. |
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I am looking to replace the absolute garbage Optolong 3nm OIII filter I got a couple years ago. Has bad halos around some stars, maybe they are IR stars, as it's not always the brightest ones in the image that have an issue. I usually remove the stars with StarXterminator, but even though it detects the stars with halos and removes them as indicated by their presence in the starfield image, they still show up as fuzzy blobs in the "star-free" image. Not always easy to edit that out with Photoshop. Anyway, I was looking into Antlia which I have seen both the 2.5 and 3nm images look pretty halo free. However, would just attaching an IR filter to my setup fix the problem? I would probably put it right on the ASI 2600MM camera so it would affect all my mono captures. Is there any real downside to having the IR filter added to every NB filtered image? I was all set to order a 3nm filter, but then saw the 2.5nm filters having better specs and supposedly 100% postproduction testing, but now it looks like that may not really solve my issue. It appears the 3nm is better, but I am concerned that on Agena Astro's website, they specifically say they won't take returns on OIII Antlia filters. I've already wasted $400 on the Optolong one, and Optlong wouldn't agree to a swap as I was outside the ridiculous 15 day window, they have, I don't want to end up with another $400 - $590 ultra-light "paperweight" |
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Hi Andrew, I have (and use) both the Optolong 3nm and Antlia 2.5nm sets. I get the same aberrations with the Antlias as the Optolongs, slightly less strong, but there… same stars, and as you say, not a function of brightness, but star composition. The filters in my opinion are still REALLY good signal wise, my set are bang-on parfocal (and with the Dark Series LRGB) and it is only the OIII where I’ve seen any issue. There are two other 2.5nm filter owners in the UK I’ve been chatting to on this and they have shared their images with me, so far we have observed the issue via FRA500, EdgeHD9.25, Redcat51, PHQ80 and RASA8. With the SY135 (strictly not fair like the RASA as beyond the quoted performance window of the filter) the aberrations are there but the Antlia 3nm is perfectly clean for the same lens and field… one guy has also had a replacement filter, but the issue persists - it’s ’live-with-able’ but not what you expect for such an expensive filter. I got these filters hoping the issue I was seeing with the Optolongs would go away, and having seen the Antlia OIII 3nm performance on the same fields (perfect), I assumed these would just be a ‘better’ version, but I’d have to recommend just getting the 3nms, unless you’re happy with a bit of extra time in Blemish Blaster or live in B9. Would be great to hear others experiences with the filters too! Ollie |
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Andrew Long: Thankfully, the replacement 2.5nm OIII filter I got from Antlia didn't have the NIR transmission problem. Would be better if these issues are caught in the QC process though. My experience comparing the 3nm OIII and 2.5nm OIII is that the 2.5nm had less haloing than the 3nm. But that could be specific to my setup. The 2.5nm Ha and SII have been perfectly fine. What attracted me to the 2.5nm was the flat top transmission curve and slightly higher transmission rather than the narrower bandpass, although I'm not complaining about blocking out a little more light pollution. Overall, the 2.5nm would only have a marginal performance advantage over the 3nm so you'd be getting better bang for your buck with the 3nm. I used the 3nm SHO (36mm) for a few years. Only reason I got the 2.5nm SHO is because I was upgrading to 2" filters. I certainly discovered that when I put an UV-IR blocker on my coma corrector, the artefacts from my dodgy 2.5nm OIII filter disappeared. There is certainly no harm in having the UV-IR blocker and I did briefly contemplate doing just that but I was persuaded to chase up Agena/Antlia for a replacement. Glad I did! |
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Ollie Aplin: Thanks, that's exactly the information and insight I was looking for. I was all set to go with the Antlia 3nm, but it sounded like some people have issues with them, and the 2.5nm are supposed to ALL be tested before leaving the factory, but sounds like they don't test the halo issue with the leaks in the 1100 + range. Another thing you mentioned about them being parfocal. That's another issue with my Optolong OIII filter, I bought the complete set too, and the OIII is 30 units out of sync with the other filters. I have to move the focus out 30 units on a Pegasus focus cube to get back into focus. I'm torn between rolling the dice with the 2.5nm and then returning it for the 3nm if I have any issues, or just going with the 3nm, which sounds like they are pretty solid in terms of QC. Thanks again! |
2.11
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Andrew Long: If it's any help, I just purchased a complete set of the new 36mm unmounted 2.5nm SHO filters along with the LRGB Dark series. I ran the filter offset calculator in Nina about 10x (instead of default 3x) and it came back nearly parafocal (maybe 1-2 steps between filters) on my Esprit 100ED with a ZWO EAF focuser from my B7 backyard here in Texas. For 3 nights I shot the western veil in a LRGBSHO 60/90/90/300/300/300 round robin schedule to check for halos on 52 Cygni and there were none with my 2600MM This is in contrast to my Player One Anti-Halo Dual-Narrowband Pro filter which did produce a small halo with my 2600MC. My scope is sitting on the shelf at a remote observatory waiting to be installed so I can't test further at this moment, but from the testing I did I was amazed at how much better the images came out with the mono+2.5 filter setup. My HFR went from 2.2px with the PlayerOne+2600MC to 1.6px with the 2.5+2600MM consistently over 3 nights. (3 nights with 2600MM and 4-5 nights with 2600MC). Hope this helps. Here's a link to the masters if you want to compare yourself: https://drive.google.com/drive/folders/1v_9pME4EA_evx6oFNm82iwqNmpddU3lz?usp=sharing Note: The 2600MC_[Ha,Oiii,Sii] are extracted from the dual-narrowband masters with DBXScript |
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John Stone:Andrew Long: Thanks a ton for the insight. This is exactly the kind of information I am looking for to make my decision. I'm really glad when I got into this hobby 3 years ago, that I started with the 2600MC, the images are amazing and it's relatively simple to work with. I became instantly addicted to AP. When I upgraded to Mono, it increased the complexity more than I anticipated, and along with having to triple your imaging time, it's definitely been cloudier the last year. I used to be able to image any night I wanted to the first couple years in Colorado. Had I started with Mono, I might have given up, but yes, the quality is just next level. Sometimes I'm blown away at just the initial stacked images from a single channel, before any processing! Detail that wasn't even in the OSC images, easily shows up with Mono, and detail that was in the OSC images, but not noticed, becomes in your face obvious. |
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Jacob Heppell:Andrew Long: One thing I didn't think to ask and may not have made clear, but I am not planning on replacing the whole set of Optolong Filters, just the OIII, so is there any issue with imaging SII Ha in 3nm and the OIII in 2.5? I wouldn't think so, even if the OIII ends up being better, sharper data, I don't think it would throw of the balance of the channels significantly, that would make it look strange. |
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I just talked to Telescopes.net to order the 2.5 nm Antlia, they have a trade up program, but they won't accept Optolong filters for trade in. LOL, Pretty much tells you all you need to know about Optolong. Too bad. I love all the other filters I've purchased with them, especially the L-eXtreme and L-Ultimate. Edit: I'll update when I get a chance to test out the new filter! |
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So my Antlia 2.5nm OIII filter showed up yesterday and I was able to take a few images before the clouds hit. But, still have the halos. Not quite as bad as the Optolong, and I have a feeling the image quality will be a little better, less background noise or light pollution in the OIII band. Here are the comparisons between the Optolong 3nm and the Antlia 2.5 nm. Both are just 6 x 300s frames stacked. The DSS image scores were about half on the antlia(400 - 600) as the optolong (800 - 900), but that was probably more due to atmosphere and possible cirrus clouds. Optolong 3nm OIII  Antlia 2.5 nm OIII  I always remove the stars for processing and then add back, so this image isn't as important as the next set, showing the stars removed with StarXterminator. I reached out to RC, and he said the software isn't designed to remove the inner reflections created by the bleedthrough from these filters. As you can see, it's able to remove more on the Antlia than the Optlong, but still not even close to perfect. Although it's easy to remove them with the blemish tool in Photoshop, the large star in the Squid nebula creates a halo that runs right into the actual squid nebula and it's pretty much impossible to remove without creating a mess where the nebula and halo meet. Optolong 3nm OIII Stars removed - Once you start stretching the image, all those little faint blobs become VERY noticeable.  Antlia 2.5 nm OIII stars removed.  |
