Thousand Oaks LP-3 Oxygen III Line Band Filter for 2" Eyepiece

Thousand Oaks LP-3 Oxygen III Line Filter – 2" Eyepiece Format

Bring Planetary and Emission Nebulae Into Bold Contrast

The Thousand Oaks LP-3 O-III filter in 2" format is your go-to tool for visually enhancing planetary and emission nebulae that radiate strongly in the doubly ionized oxygen (O-III) line at 500.7Å. Designed for visual observers working under light-polluted or naturally hazy skies, this narrowband filter dramatically increases contrast, even when sky conditions aren’t ideal.

The LP-3 isolates the O-III line while sharply cutting off surrounding wavelengths, including light pollution, moonlight, and atmospheric airglow. The result? Nebulae like the Veil, Helix, Dumbbell, and Lagoon appear more defined and stand out against a much darker background sky.

With its standard 2" threaded format, the filter is ideal for pairing with long focal length eyepieces for wide-field views of large nebulae—especially in medium to large aperture telescopes.

Key Features:

• Narrowband O-III Transmission: Passes only the 500.7Å oxygen-III line to enhance key nebular targets

• High Contrast Boost: Suppresses all background light and unwanted spectral lines

• Ideal for Planetary & Emission Nebulae: Greatly improves visibility of the Veil, Helix, Swan, Dumbbell, and more

• 2" Eyepiece Compatibility: Fits all standard 2" threaded eyepieces and filter wheels

• Durable, Precision Optics: Made in the USA by Thousand Oaks Optical

Recommended Use:
Use in a medium-to-large aperture telescope under dark or moderately light-polluted skies. Best paired with a long focal length 2" eyepiece for wide fields and a 4–6mm exit pupil. Particularly effective on planetary nebulae, bright supernova remnants, and high-surface-brightness emission nebulae.

Not for Use with Galaxies or Star Clusters:
This is a specialized nebula filter, not intended for broadband use or for viewing stars and galaxies.

How to Choose the Right Eyepiece for Your Filter

Not sure which eyepiece will give you the best view with this filter? Here's a quick tip:

The brightness of a nebula (and how well a filter performs) depends on something called the exit pupil—the size of the light beam exiting your eyepiece and entering your eye. For most filters, certain exit pupil sizes give you better contrast and visibility depending on your sky conditions.

To find the right eyepiece (your target eyepiece), just enter your telescope's focal ratio (like f/5, f/10, etc.) in the calculator box below. It will show you which eyepiece focal lengths work best under different skies:

• Dark Sky, Large Nebulae → Use a long focal length eyepiece for a large exit pupil (6–7mm)

• City or Suburban Skies → Use a medium eyepiece for a moderate exit pupil (3–5mm)

• Smaller Nebulae or High Contrast Needs → A shorter focal length eyepiece for a smaller exit pupil (2–3mm) may help

• O-III Tip: For best contrast on planetary nebulae, try using an eyepiece that gives you a 3–5mm exit pupil under city skies, or up to 6mm under dark skies.

Tech Details: