1.25" O-III Filter - Enhances Contrast During Visual Observation of Gaseous and Planetary Nebulae in All Sky Conditions, the Veil, Ring, Dumbbell and Orion Nebula, Among Many Other Objects

I'm a hardcore deep sky veteran now on my 5th scope, an 18-inch Dobsonian. On a whim, I decided I needed a filter with an even tighter bandwidth than a UHC (ultra high contrast) filter to try on the Vela Supernova Remnant from the ultra-dark skies of Big Bend National Park, Texas. I was afraid to get this one because of its low price but I was on a budget and in a hurry. I'm glad I got it. It worked. Freezing my tail off at 3 in the morning on a cold, crystal clear November night I got the view I wanted. It was a disappointment on any object that shines brightest in hydrogen light, but if you know what nebulas shine in oxygen III light like the Veil, get this filter. You'll be glad you did.

The AstroMania 2" O-III Filter is a great value! Packaging/Shipping: I was once again very impressed with how well AstroMania did packaging this filter. I've included some pictures from the unpacking process showing how securely it was packaged. Shipping information was sent to me by AstroMania and the package came in within the time frame given. The filter itself comes in a very nice plastic case that is even better than what I has come with other more-expensive filters. Since this is the only O-III filter I have, I wasn't able to compare it visually to other branded filters, so I instead compared it to UHC filters (one from Astromania, another from DGM Optics). The AstroMania filter easily threaded onto my eyepieces with no problems. My observing location was near a large city, so there was some light pollution, but I drove about 40 miles North of the city to a spot where I was just getting the Milky Way naked-eye overhead. It was about 4am CST with no moon, 70 degrees and average seeing/transparency. I was using my Orion SkyQuest XT12G with 82 degree Explore Scientific eyepieces. I looked at the following objects during my testing: NGC 6960 Veil Nebula - Wow!! The Veil Nebula is unbelievable using an O-III filter. I was literally walking around the Veil nebula North and South pieces and couldn't believe the details that were brought out with this filter. The central piece was not seen, but I chalked this up largely to the sky conditions where I was (not great) and that the central area has a much lower surface brightness and is hard to see. The UHC filters couldn't compare to the O-III on this object, but they did bring out the visibility over no filter at all. M57 Ring Nebula - While there were some differences visible with the O-III over no filter at all, the UHC filters really stood out on this object. NGC 6543 Cat's Eye Nebula - This was one of the objects that definitely stood out with the O-III over the UHC filters. While this object is pretty small, the detail and color really stood out and was greatly enhanced with this filter. While I've seen this object in the past without a filter, I really wanted to spend time studying it with the O-III. M27 Dumbbell Nebula - The Dumbbell nebula, while much better with the UHC filters, was greatly enhanced by the O-III filter and gave a wonderful view versus no filter at all. My conclusion after using the O-III filter from AstroMania was that if you want greatly enhanced views of many, many nebulae in the sky, this filter will do the job and then some, at a very reasonable price. Some very experienced or professional observers might opt for something that brings out more detail, but with that comes a much higher price. I was very impressed, once again, with the product AstroMania put out.

The published spectral transmission plot shows only the visible light range. If you're using this on a monochrome camera without an IR-block filter, be aware this filter does not attenuate IR very much, in fact it has more transmission at 840 and 920 nm than it does in the nominal passband of 500-520 nm. Attached plot of absorbance was taken with an Ocean Optics USB2000 spectrometer.

I found the filter threading to be great, the filter clean and the shipping fast! Just a note: this filter will produce a green image with one-shot color cameras. I have tested it and found that it cuts up to 1 full f/stops of light so that means that your exposure time is going to be at least 2X longer than your exposure without the filter. I tried this out on M 27 (The Dumbbell Nebula) and it did an awesome job of separating the OIII from the nebula (greenish image). The second image is what the colors were like without any filter (notice that the reds show up in this unmodded DSLR image). Astromania also gives great discounts if you order more of their stuff at one time. I did and saved $$$!

While it appears that the filter does do a decent job of allowing Oiii wavelength through, I am getting some very serious halo effects on some of my stars. I'm not sure what is causing this, but of the many filters I have, this is the only one that I'm having an issue with. Unfortunately, this makes unusable for my purposes. I've included a picture that demonstrates the problem.

Use this in 2” T Adapter with Nex6 body. Great images of DSO. Highly recommend.

Using this excellent quality filter for a Unistellar Telescope. It does as it is supposed to do. Very satisfied with it.

Good item .

Excellent clarity. The OIII nebulae stand out wonderfully in the visuals and in the photos. I tried, from dark skies, searching for the Veil nebulae even using the DGM optics nebula filter but with disappointment. However, with this filter, I found it in no time - see attached image. The nebula filter is great to block stray light and increase over-all contrast but for specific targets, I found the OIII filter to be a wonderful tool. The shipping is extremely slow but the seller is very quick to respond to any questions and help out as necessary.