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Optolong LRGB Filter Testing and Comparison with Baader LRGB Filters

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Optolong LRGB Filter Testing and Comparison
with Baader LRGB Filters

By Terry Hancock

I was recently contacted by Optolong, a filter manufacture in China who asked me to test their filters. They sent me a set of 36mm un mounted LRGB and a set of 36mm Narrowband Filters, H-Alpha 7nm, OIII and SII 12nm. I was impressed when they arrived, nice packaging and presentation in a similar plastic case to the Baader. I limited my comparison for LRGB only which was carried out on the 15th and 16th August with similar average seeing conditions. The narrow band filters are not the final version that will be used for comparison. At the time they were only manufacturing them in 12nm pass band. The Baader equivalent is 7nm, which is more the industry standard. Sub sequentially they have started producing the narrow band filters in 7nm pass bands. They will have to wait for another day…

Optolong are not new to manufacturing Astro Filters. Established in 1999 they are a subsidiary of Yulong Optics Kunming City China. Their products include Astronomical Filters, Band pass Filters, Fluorescence Filters, Edge filters, Long pass & Short pass Filters, Beam spliters, Anti-reflective Coating and Optical Mirrors. They are Quality assurance certified ISO9001.

Optolong literature states:

LRGB Filters Optolong

  • German Shott glass 2mm thick enabling parfocal performance
  • Anti-reflection coating to eliminate halos
  • Steep band pass filters to eliminate UV and IR interference

For the test the 36mm un mounted filters were fitted to a QHYCFW2-M-UltraSlim Filter Wheel. Camera used was a QHY23 Monochrome CCD, Telescope used was a Astro Tech AT130-EDT APO Refractor @ F5.6.

Optical spectrum diagram (optical curves) by Optolong

I first checked the Minimum and Maximum ADU to help determine if there is any difference in color transmission. Here is the result:

Baader August 15thOptolong August 16th
Minimum 539-772Minimum 745-751
Maximum 44405-46106Maximum 45050-46088
Minimum 639-784Minimum 733-748
Maximum 43749-45815Maximum 44891-45787
Minimum 573-784Minimum 733-753
Maximum 42253-44262Maximum 42150-45189
Minimum 512-769Minimum 742-754
Maximum 41932-43622Maximum 41773-43586

Based on the above I find the color transmission to be very similar.

Next I checked for any halos using the bright star 52 Cygnus at the center of the image as reference and I found that the Baader Green and Blue Filters exhibited a much stronger halo than the Optolong.

Both the Baader and Optolong Luminance and Red filters showed only very faint halos.

I found no difference at all between the Baader and Optolong for either sharpness or contrast.

Neither Baader nor Optolong distribute reflections for this test target.

I found both the Baader and Optolong LRGB Filters are parfocal when used with this equipment.

One thing I find strange is that with the Baader Filters the bright star at about 8 o’clock to 52 Cygnus showed a spike in all filters except the blue filter. No such spike at all with any of the Optolong Filters.

Retail Price in US Price Comparison 36mm un mounted set of LRGB

Baader $477.00 per set

Optolong $299.00 per set


After taking identical images with the Optolong and Baader filters I was amazed at how similar the images were. The preceding images speak for themselves in large part. A closer observation of the images taken with Optolong filters, I found no noticeable reflections especially around the bright stars. Images showed excellent contrast with clear differentiation of colors.

The Optolong LRGB Filters offer similar to somewhat superior performance and quality to the Baader Filters at roughly 63% of the cost. This makes the Optolong filters a great value for the money. Optolong Filters can be purchased from the US Distributor www.astrofactors.com

  • Urban Observer, okiestarman56, leonidman63 and 5 others like this


Thanks Terry for this nice review.



    • turbo399 and jdmjrslm like this

Thanks. BTW StarGuy/Mr StarGuy is selling Optolong filters under his own name including 1.25" and 2" LRGB sets.

    • turbo399 likes this
Really a nice review. It's good to know there's some more players out there making high quality filters.
    • turbo399 likes this
Sep 23 2015 04:59 AM



Neat review - short and sweet!


I am no imager - strictly visual but used to seeing minute details - but I see a "substantial" difference in favor of the Baader filters except for the Red one which is nearly identical.


Of course this could be attributed to the conditions prevalent on the two days you imaged. Also, you have the high quality/resolution photos available VS the reduced resolution when you upload to CN.

    • turbo399 and dvalid like this

Great review, Terry.  I guess we should assume the same with the narrow-band filters.

    • turbo399 likes this

Sweet :)

    • turbo399 likes this
Sep 24 2015 12:35 AM



Any chance of making the raw files available? As I mentioned - to my eyes at least - there is significant difference in favor of the Baader filters. However, viewing low resolution photos and comparing between them is not the best methodology to ascertain the true extend of the difference in performance.


Also, can you please report on the general conditions prevailing between the two evenings? In your report you don't mention if one evening was better overall than the other - something that could impact on the quality of the images.


Unless there is a hidden factor in favor of the cheaper Optolong filters, based on the images alone, I would go straight for the Baader filters were I an imager. If one is budget conscious or just starting and doesn't want to commit the extra $178 (maybe put the funds to the purchase of another accessory), the Optolong filters make sense. Otherwise, I can't see why one would not get the Baader filters  :scratchhead:  :shrug:

    • Waldemar likes this

thanks everyone, petert913 I am expecting 6.5nm Optolong Narrow-Band Filters to arrive soon for further testing. 



In my very first paragraph I wrote "carried out on the 15th and 16th August with similar average seeing conditions"


Here are the same images/clips shown above in higher resolution, you should be able to download from the following dropbox link https://www.dropbox....gT6zkBNAga?dl=0

Sep 24 2015 09:28 AM

Thanks Terry!


Missed that bit about the weather conditions - my bad.


Just had a quick look at the Dropbox photos. Red one - difference so marginal I would have to say I couldn't see any appreciable difference. Luminance - slight nod to the Baader. Other two - very clear nod to the Baader.


Seeing the images in better resolution does help. If money is no object then the Baaders for sure. There is appreciable difference - yet not huge. However the Optolongs are quite good. $178 may not seem much, but it is still a 37% price difference to the Baaders and does buy one some more accessories as I mentioned.


I have attacked the Veil visually with apertures of 50, 60, 70, 80, 90, 102, 120, 152, 300 and 450mm (all but the last 2 refractors - last two premium Dobsonians) over the course of a few years and that's why I am so "critical" of the images in both the review and the Dropbox link as I can relate to them - they feel like the views I get through the eyepiece in the two larger instruments - especially the 18".


Is there a chance to see the end result for both filter sets? There is only one true color photo at the end of the review - I assume with the Optolongs - which is an excellent photo by the way. It would be nice to do a comparison of the final output. In color I expect any differences to be negligible which would make the Optolongs an even better value proposition, but would enjoy the comparison if you could provide the side-by-side view like the others.


Overall, it is good to see alternatives coming to the market. It challenges established players to raise the bar for their products or reduce prices and of course gives valuable experience and feedback to the creators of new products to come up with better versions in the future.

thomas glynn
Oct 27 2015 08:57 PM

Where can I buy a set of 36mm unmounted LRGB filters for $299.  I'd also like a set of narrow band filters also.  



Did you ever get the narrow band filters?  If so, how did they do?  I've been planning to make the jump to CCD and will be getting LRGB and narrow band, so this info is very helpful!



Hi Terry, I'm not an experienced astro-photographer but I do appreciate a good review no matter what the product. I must say some of your responders were a little to critical of your observation of this product, but I found It to be Informative and very well written. So keep up the good work. Steve

Is the red spectral curve accidentally shifted to the right? Or is it true, that yellow is blocked out by the RGB set and additional IR is included over what the luma filter lets through? This must affect color balance.


Clear Skies!


I find the filter market a little bit like dog eat dog at the moment. We have Astronomik making claims that Optolong stole there technology using methods that would not be out of place in a James Bond film. I then read that Astrodon were taking a pop at what I presume is Baader (but not stated- as they seem to be the only company I can find with a 3.5 nm HA Filter). The market may be competitive but I find all of this very distasteful.


It is very much up to the user to test product to there satisfaction & complain to the manufacturers if they find anything amiss. Manufacturers and distributors squabbling among themselves is by its very nature distasteful & unprofessional. 


Never has the statement Caveat Emptor been more true!

    • turbo399 likes this

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