Product Description

The OIII narrowband filter isolates just the two doubly-ionized oxygen lines (496 and 501nm lines) emitted by planetary and emission nebulae, while blocking the rest of the overall spectrum of light. The result is extreme contrast between the black sky background and the faint photons of OIII light needed for detailed views of the Veil, Ring, Dumbbell, Crescent and Orion nebulae, among other objects. Each filter has an ultra hard, vacuum-deposited coating carefully designed to block all of the visual spectrum ranging from 400 to 700 nm. This eliminates the un-natural colored halos surrounding bright stars common with O III filters of less sophisticated coating technology.

Product Details

• Brand: Celestron
• Model: 93624
• Dimensions: .5 pounds

Features

• For viewing many common nebulas
• Reduces glare and light scattering
• Increases contrast through selective filtration
• Made of high quality, solid plane parallel glass with excellent homogeneity
• Anti-reflection coated to prevent glaring and ghosting

Amazon.com Product Description
The Celestron 93624 Narrowband Oxygen III 2-inch filter is a remarkable advance for the serious visual observer of emission nebulae. One of the biggest advantages of narrowband filters is that by passing only the light emitted by nebulae, light from artificial sources like street lights is blocked. This allows you to take detailed exposures of nebulas from a suburban location that can rival shots from much darker sites. The Celestron 93624 is made of high quality, solid plane parallel glass.

Customer Reviews

Celestron 2-inch O-III filter
I can't compare this filter to its counterparts from Lumicon, Orion, Thousand Oaks, or others, since I don't own and haven't tried any of them. Physically, the Celestron looks identical those offered by Baader Planetarium--I've never seen any other make with those square serrations along the perimeter.

We still haven't been out to our dark site with the O-III yet, but I did give it a quick try a few weeks ago at our local community college, where we usually just do planetary viewing due to the excessive light pollution. I inserted the O-III in our filter slide and pointed it toward M57, not expecting very much. After all, the Ring is supposedly better suited to a UHC filter than the O-III. The results were absolutely stunning--the nebula appeared as a distinct greenish ring against an inky black background. I then changed to a longer FL EP and directed our CPC 925 to slew over to M27. Usually we can't see the Dumbbell from the college and that night was no exception. Not knowing whether it was even in the FOV, I slid in the O-III filter and the nebula just popped right out, nearly dead center, and with as clear definition as we usually get from the dark site (Bortle's green) with no filter at all.

We will definitely be picking up the UHC and h-beta filters to join this one. At more than twice the price, I can't imagine how the Lumicon O-III could be twice as good as this one, so I'm very satisfied with the Celestron filter, both in performance and value.

Celestron 2" Oxygen III filter
"Nebula filters" are intended to darken the background sky while allowing specific wavelenths of light to pass through so faint objects are easier to view. These filters perform best on nebulous objects. They are less effective when observing galaxies and clusters and in some cases make such objects too dim to view.

I recently used the filter on both M-57 and M-27. The Celestron OIII did an excellent job darkening the sky and increasing contrast between the objects and the background.

If you are in the market for this type of accessory, Celestron's version performs well and is inexpensive.