Products that keep you in tune with the Universe throughout the night.

Nebular Filters To Block Light Pollution And See Incredible Detail. These filters are manufactured specifically for AS Research and include edge-blackening of the filter glass and AR coatings both of which improve the contrast of the view when using them.

Need a good nebular filter?

Take advantage of AS Research Filter Sale.

Purchase a 2" O-III and 2" UHC filter together as a pair,

and get your choice of either a 1.25" O-III or 1.25" UHC at a reduced cost!

1.25 and 2-inch UHC Filters and Graph.jpg

The UHC Filter isolates and passes the Hydrogen-beta line at 486nm and both doubly-ionized Oxygen lines at 496nm and 501nm.

The Ultra High Contrast Filter, UHC, blocks light pollution and will show you the most of any gaseous emission of diffuse or planetary nebulae, and, by allowing through the two C2 emission lines improves the view of comets! With a UHC filter, objects which might ordinarily be difficult or nearly impossible to see appear in stunning detail.

Transmission values of the important wavelengths;

H-beta, 486nm: 95.6%

O-III, 496nm: 97.5%

O-III, 501nm: 97.6%

A good filter for a great price...

1.25 and 2-inch O-III Filters and Graph.jpg

The O-III Filter blocks Hydrogen-beta line at 486nm and transmits both of the doubly-ionized Oxygen lines at 496nm and 501nm.

The Oxygen-III Filter, O-III, will provide the absolute highest contrast views of many diffuse and planetary nebulae passing only the doubly-ionized Oxygen light.


When you can get an AS Research nebular filter (and a couple of nice dinners out, too, for what some filter companies charge for just a filter); many say that the AS Research nebular filter is the BEST filter!

The BEST nebula filters - are not just what they show you in the sky.

It is also what they leave in your wallet $$.

Here are reviews by actual users of the AS Research filters.

AS Research O-III filter by "J.L."

"Last Tuesday several of us went up to [northern Michigan]. Tuesday and Wednesday were great with Wednesday being the best night. The seeing was fabulous. The star images in my 15" were the best I have ever seen. The stars were like diamonds. It was incredible. I knew my mirror was good, but I didn't realize how good it was. Said a lot too for the eyepieces - and my collimation. With that being said, it would be a great night to compare my O-III filters - AS Research and my Astronomik - both 2". End result - both filters are comparable. Both are very good. The only difference I could see is that perhaps yours gave a somewhat (and barely somewhat) brighter overall image with slightly less contrast. This was done by flipping back and forth with my filter slide quickly trying to see any difference. In reality, if I went away from the scope and came back and someone changed filters, I doubt I would be able to say which filter I was looking through. The others didn't see any discernible difference either. So, in all, with both filters being equally good, yours wins as it is cheaper!"

AS Research O-III and UHC filters by "Bob"

"Two weeks ago I did a Lumicon filter comparison with my new 1 1/4" Apache-Sitgreaves OIII and UHC filters. I could tell no difference between the two using my 8" dob on M27, M8, M17, and for the OIII it was the Veil Nebula.

I have to say for the price difference I was impressed."

AS Research O-III and UHC filters by "W.G."

"After a side by side comparison we did using my new Apache-Sitgreaves filters against my friends Lumicons, we could tell no quality difference in nebula viewing. The only difference was the cost savings in my wallet. Way less expensive then the Lumicon filters."

I'm sure most will agree."

AS Research O-III and UHC filters by "B."

"I looked through these filters at a star party. The views were nice! JMO. Bob.

AS Research O-III and UHC filters by "BB"

"I loved the new filters!"

AS Research O-III and UHC filters by "Norme"

"Transmission looks superb.

AS Research O-III filter by "R.B."

"I tried D.B.'s AS Research filter and loved it. Can't wait to receive it.

AS Research O-III filter by "J.T."

"The OIII filter was amazing! Beautiful and Bright Veil Nebula in a 6" refractor. Easily as visible as it was in my 8" SCT from moderately dark skies of Michigan."