Thousand Oaks LP-2 Narrowband Filter for 2" Eyepieces

Thousand Oaks LP-2 Narrowband Filter – 2" Eyepiece Format

High-Contrast Nebula Views, Even from the City

The Thousand Oaks LP-2 is a 48mm narrowband filter designed for visual observers who want to cut through light pollution and see emission nebulae in greater detail—even from the suburbs or city. With a generous 280 Ångstrom passband, it transmits strongly at all three key nebular emission lines: hydrogen-beta at 4861Å and oxygen-III at 4959Å and 5007Å, while sharply blocking unwanted light from streetlights, skyglow, and moonlight.

The result is a darker sky background and dramatically improved contrast on nebulae like the Veil, North American, Helix, Rosette, Dumbbell, and Lagoon—even under less-than-ideal conditions. It also performs beautifully under dark skies, making faint nebulae easier to detect.

Unlike conventional narrowband filters with soft transmission edges, the LP-2 features very steep passband cutoff slopes, helping it deliver roughly twice the contrast of a typical broadband filter. All coatings are safely sealed between two layers of optical glass for durability and easy cleaning, even if your lens cloth gets a little enthusiastic.

Key Features:

• 280Å Narrowband Passband: Covers the critical H-Beta and O-III emission lines at 4861Å, 4959Å, and 5007Å

• Exceptional Transmission: 95–96%+ at key nebular wavelengths for brighter, bolder detail

• Very Steep Cutoff Slopes: Suppresses unwanted wavelengths with higher contrast than standard narrowband filters

• Visual Use Only: Not intended for imaging or reflection nebulae

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

• Durable Coatings: All coatings are sandwiched between glass for long life and easy cleaning

• Made in the USA: Quality you can rely on from Thousand Oaks Optical

Recommended Use:

Ideal for medium and large aperture telescopes, especially when paired with medium to long focal length 2" eyepieces. Performs well in both light-polluted environments and dark-sky sites, revealing nebulae with improved contrast and visibility.

Not for Imaging or Reflection Nebulae:

This filter is designed strictly for visual use on emission nebulae. It will not enhance views of galaxies, star clusters, or reflection nebulae.

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

LP-2 Tip: For general-purpose nebula viewing under light-polluted skies, a 3–5mm exit pupil offers the best balance of brightness and contrast. Under dark skies, stretch to 6–7mm for wide, immersive views of large emission structures.

Tech Details: