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Celestron 93623 Narrowband Oxygen III 1.25 Filter
The 1-1/4" 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
Made in China
Package Dimensions : 3.0 L x 1.0 H x 3.0 W (inches)