GSO 1.25" IR Block Filter

Our Price: $33.00
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In stock (10+ Available)
Ships by Next Business Day
Our Product ID: OFIL-GS-AD071
Manufacturer SKU: AD071
Item Can Ship: Worldwide
GSO 1.25" IR Block Filter

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Quick Overview

  • GSO filter uses dichroic optical coating to block IR light from entering digital cameras, preventing star bloating and increasing sharpness of Moon and planets
  • Sharp cut-off at 690 nm blocks IR light while passing visible red light, especially the important 656 nm hydrogen-alpha emission line
  • Made of flat, scratch-resistant optical glass to maintain image quality
  • Threads to camera, eyepiece, or adapter with standard 1.25” threads, and can be stacked with other threaded 1.25” filters
  • Comes with protective, foam-lined, plastic storage case.

Product Details

An infrared filter (also called an IR Block filter) is a very important accessory for imaging with today's CCDs, digitial cameras or webcams. Imaging sensors in these cameras are sensitive to visible light as well as to infrared wavelengths. As a result, images of stars might be bloated and lunar and planetary images will be soft.

GSO's IR Blocking filter is recommended for use with CCD, video & webcams for sharper images. It threads on to any CCD camera, eyepiece, or adapter that accepts 1.25" filters. Such filters are required when imaging with refractor telescopes. Compound reflectors (like Schmidt-Cassegrain and Maksutov-Cassegrain telescopes) will also benefit from an IR-block filter to some extent. Even imaging through Newtonian telescopes will benefit since IR filters will reduce "IR bleed". As an added advantage, use of this filter also acts as a dust cover for the sensitive CCD chip in imaging devices.

This filter has an extremely sharp cutoff at 690nm, yet it transmits all the visible red wavelengths (including the important 656nm H-alpha emission line) and prevents IR wavelengths from blurring fine detail in your digital images. GSO does not provide a transmission curve for its filter but we had one tested at the physics lab of a local college. The tested unit had peak visible light transmission of over 95%. GSO does not claim that this filter also blocks out UV wavelengths.

The filter cell is beautifully machined and black-anodized with threads on both sides (male on one side and female on the other), so you can stack this filter with other 1.25" filters. Its clear aperture is a full 26mm. The filter glass is scratch resistant and the filter can be used with a telescope of any f-ratio. The glass substrate is of very high optical quality, so it can be used in front of a lens without degrading the image quality. In fact, the GSO filter is a more expensive coated "dichroic" filter that displays a pinkish reflecting tint, as opposed to cheaper "absorbing glass" IR block filters which exhibit a greenish tint.

The GSO IR Blocking filter ships in a protective, foam-lined, plastic storage case.


Total item length (including external male thread) = 11.1mm (0.44")
Clear aperture = 26mm (1.02")
Weight = 0.2 oz.
Made in Taiwan

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