S-series IR850nm 1.25" IR-Pass Filter

Product Overview

The Player One Astronomy S-series IR850nm 1.25″ is a deep near-infrared long-pass filter that admits light beyond 850 nm and blocks the visible band to OD3. Its cut-on sits further into the infrared than the IR685, pushing even harder against atmospheric turbulence for the steadiest possible planetary and lunar detail when seeing is rough. It transmits about 90% in-band on a multi-layer coated optical-glass substrate.

Who It's For

This filter is for high-resolution planetary and lunar imagers running an infrared-sensitive monochrome camera who want the deepest practical IR cut for turbulent nights. If you image the Moon or planets such as Mars and want a stronger seeing-buster than a 685 nm filter, or you experiment with infrared views of Uranus, the IR850 is built for it.

Key Features & Design

• 850 nm long-pass: transmits deep near-infrared beyond 850 nm, where seeing has even less effect than at 685 nm.
• Visible blocking to OD3: rejects shorter wavelengths so only the deep near-IR reaches the sensor.
• ≈90% in-band transmission: preserves as much of the available IR signal as possible.
• Multi-layer composite coating: on a high-quality optical-glass substrate.
• 1.25″ thread (M28.5×0.6): fits standard 1.25-inch cells, drawers, and wheels.

Optical/Mechanical Design

The IR850 is a long-pass interference filter with a cut-on near 850 nm: it transmits about 90% above that point and blocks the visible band to optical density 3 (OD3). Pushing the passband deeper into the infrared than a 685 nm filter reduces the effect of atmospheric turbulence further still, at the cost of less available light — deep-IR imaging generally needs a sensitive camera and longer exposures. The 2 mm-thick optical-glass substrate carries a multi-layer composite coating. Mechanically it uses the 1.25-inch M28.5×0.6 thread with a 5 mm body plus 2 mm thread section (7 mm total).

Recommended Uses

• Deep near-infrared planetary and lunar imaging in poor seeing with a sensitive IR camera.
• Maximum seeing suppression where a 685 nm filter is not aggressive enough.
• Infrared experiments on targets such as Uranus with monochrome cameras.

Compatibility & Accessory Notes

• Fit: 1.25″ M28.5×0.6 filter thread — works in 1.25-inch cells, drawers, and filter wheels.
• Cameras: best with a camera that keeps strong sensitivity out to 850 nm and beyond, typically monochrome.
• Backfocus: the 7 mm cell and 2 mm glass add to your optical path; include them in your spacing calculation.

Good to Know Before You Order

• Because the passband sits deep in the infrared, expect less signal than a 685 nm filter; plan for a sensitive camera and longer exposures.
• This is an imaging filter that passes light your eye cannot see; it is not intended for visual observing.
• Player One does not publish a net weight for this filter, so the shipping weight shown at checkout is an estimate. Contact us if you need an exact figure.

FAQ

Is it difficult to set up? No. It threads into a standard 1.25-inch filter cell, drawer, or wheel and needs no power or configuration; refocus once after fitting, since deep-IR focus can differ from visible.

How is this different from the IR685? The IR850 cuts on further into the infrared (850 nm versus 685 nm), so it suppresses seeing more strongly but passes less total light.

Do I need a special camera? Yes, in practice. A camera with good sensitivity beyond 850 nm, usually monochrome, gets usable signal because only deep near-IR passes.

Can I use it for visual observing? No. It transmits deep near-infrared the eye cannot use; it is an imaging filter.

Bottom Line

The S-series IR850nm 1.25″ filter pushes imaging deep into the near-infrared beyond 850 nm with ~90% transmission and OD3 visible blocking, giving planetary and lunar imagers the strongest seeing suppression in Player One's IR-pass line.