Brightwell Dawnline light pollution filter 2 in

Specifications

Description

The Dawnline light pollution filter 2 in is a broadband filter in a 2 in threaded cell. It reduces transmission of the strongest emission lines from older street lighting, including the sodium line near 589 nm, while passing a wide portion of the visible spectrum. Stars and deep-sky objects keep a close approximation of their natural color, with a moderate loss of overall brightness.

Sky glow from artificial lighting does not always come from narrow lines, so the effect of this filter depends on the type of lamp near your observing site. It gives the greatest improvement under low-pressure sodium and mercury-vapor lighting. Under modern white LED lighting, whose spectrum is broad and continuous, the improvement is smaller. By reducing the background glow, the filter raises contrast, so the nebula itself does not become brighter. Under suburban skies, faint galaxy arms and the outer edges of large nebulae can become easier to trace.

Good targets include the Andromeda Galaxy, the Pleiades, the Double Cluster, and the Orion Nebula. Emission nebulae respond more strongly to narrowband filters such as UHC or OIII, which block more of the background, so this filter suits broadband targets. The filter dims the view, and it is most useful in telescopes of 6 in aperture and larger under moderately light-polluted skies.

The filter threads into 2 in eyepieces, 2 in diagonals, and 2 in filter adapters with M48 x 0.75 threads. Handle the glass by the cell edges and store it in its case when not in use, since contact with other optics can scratch the coatings.

About this configuration

The Brightwell Dawnline light pollution filter 2 in is offered in several configurations, and the notes below describe what this particular one includes. The standard grade uses the same coating design as the higher grades, with wider tolerances on flatness. Standard grade glass suits visual observing at low and medium magnification. Anti-reflection coatings on both faces reduce halos around bright stars in the field.

The filter ships in a clear plastic case that keeps dust off the glass between sessions. The 2025 edition keeps the same transmission figures as the earlier years of the Dawnline line. A filter does not make objects brighter; it darkens the sky background more than the target, which raises contrast.

What's in the box

• Light pollution filter in 2 in threaded cell
• Plastic storage case
• Plastic storage case

Compatibility notes

• Threads into 2 in eyepieces, diagonals, and filter adapters (M48 x 0.75).
• Most effective in telescopes of 6 in aperture and larger under light-polluted skies.