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Baader Planetarium red long-pass filter in 1.25 inch threaded cell

Baader Planetarium

Baader Planetarium Red 610nm Long-Pass Filter 1.25" optic

SKU CH-5R1S-5KZ2G

Isolates red wavelengths at 610 nm for enhanced planetary and lunar contrast with 98 % transmission and plane-parallel polish to 30 arc seconds

  • Enhances planetary contrast by isolating 610nm red wavelengths
  • Maintains optical integrity with 98% transmission efficiency and 2mm precision glass
  • Eliminates ghosting through substrates polished to within 30 arc
  • Prevents vignetting at any focal length with maximum clear aperture
  • Reduces urban light pollution by blocking unwanted wavelengths for clearer views

Red 610nm Long-Pass Filter

The Baader Planetarium Red 610nm Long-Pass Filter threads into 1.25" eyepieces and transmits a narrow red band centred on 610nm. It is designed for visual observers and imagers who want to increase contrast on planetary and lunar targets. The filter works with telescopes of any focal length and can be placed anywhere in the optical train.

98% transmission at 610nm

The single specification that decides suitability is the 98% transmission efficiency at the 610nm bandpass. This high throughput preserves image brightness while isolating the red wavelengths that reveal Martian deserts, Jovian cloud belts and lunar maria. If your target emits strongly in other colours, a different bandpass will serve you better.

Optically polished 2mm substrate

The 2mm thick glass is plane-parallel polished to within 30 arc seconds, eliminating wedge-induced ghosting or double images during long sessions. The largest clear aperture on the market prevents vignetting even at fast focal ratios. The filter cell adds no astigmatism, so sustained high-power views remain sharp across the full field.

Highlights

  • Enhances planetary contrast by isolating 610nm red wavelengths
  • Maintains optical integrity with 98% transmission efficiency and 2mm precision glass
  • Eliminates ghosting through substrates polished to within 30 arc
  • Prevents vignetting at any focal length with maximum clear aperture
  • Reduces urban light pollution by blocking unwanted wavelengths for clearer views

Specifications

No published specifications for this item yet.

Questions about this item

How does the 610nm long-pass filter change the view at the eyepiece?

It transmits wavelengths above 610nm with 98% efficiency, boosting contrast on Mars, Jupiter and the Moon while blocking shorter wavelengths that wash out surface detail.

What does the 1.25" thread standard mean for compatibility?

The filter screws directly into any 1.25" eyepiece or accessory barrel, and its maximum clear aperture prevents vignetting at any focal length.

How thick is the glass and how flat is it polished?

The substrate is 2mm thick and plane-parallel polished to within 30 arc seconds, so it adds no astigmatism or ghost images when placed anywhere in the optical path.

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