Pellucid Selene lunar filter 2 in, observatory grade

Specifications

Description

The Selene lunar filter is a neutral density filter in a 2 in threaded cell, designed to reduce the brightness of the Moon at the eyepiece. It transmits about 12 percent of incident light across the visible spectrum, so surface detail stays visible while glare falls substantially. Because the filter has no passband, it does not isolate any emission line, and it does not shift the color of the image in a noticeable way.

Near full phase, the lunar surface is bright enough to cause discomfort and loss of contrast at high magnification, and the bright limb can overwhelm the eye. Lowering the light level lets you see terminator shadows and crater floors with less dazzle, and it helps you keep your dark adaptation when you switch to fainter targets afterward. The filter also helps with bright planets such as Venus and Jupiter, whose images can wash out at high power.

The filter threads into the front of any 2 in eyepiece or the nosepiece of a 2 in diagonal, and it can be mounted on a 2 in filter adapter for other accessories. Use it for lunar and planetary observation only. A neutral density filter does not reduce sunlight to a safe level, so never use this filter to view the Sun through a telescope or binoculars, because the risk of permanent eye injury remains. Store the filter in its case when not in use to protect the glass from dust and scratches.

The glass is ground to a uniform thickness and coated on both surfaces with an anti-reflection layer, which limits internal reflections and ghosting. The transmission is consistent across the field, so the view remains even at the edges of the eyepiece. Clean the glass with a soft brush and a lens cloth, and avoid touching the optical surfaces with bare fingers.

About this configuration

The Pellucid Selene lunar filter 2 in is offered in several configurations, and the notes below describe what this particular one includes. The observatory grade comes with a measured transmission curve for the individual filter in the box. Observatory grade glass has the tightest flatness tolerance in the Selene line, which suits imaging with long focal lengths. The hard-sputtered coating resists scratches and humidity, so the filter tolerates cleaning better over the years.

The filter ships in a clear plastic case that keeps dust off the glass between sessions. The passband in the 2024 edition matches the other years; the changes concern the housing only. Check the size in the specifications against your eyepiece barrels, star diagonal, or filter wheel before you choose.

What's in the box

• Lunar neutral density filter in 2 in threaded cell
• Padded storage case
• Test report with measured transmission curve
• Plastic storage case

Compatibility notes

• Threads into 2 in eyepieces, diagonals, and filter adapters (M48 x 0.75).
• Usable with any telescope that accepts 2 in accessories.