Astronomik IR-Block 1.25" filter (Astronomik, SKU: 10230125) is an infrared-cut filter intended primarily for lunar and planetary imaging with IR-sensitive cameras. It preserves visible light while reducing radiation that may focus in a different plane and soften the image.
IR-Block is suitable when the camera has low ultraviolet sensitivity. It should not be treated as a full UV/IR-Cut filter. If the sensor also records UV, Astronomik UV-IR Block is the appropriate option. The improvement depends on camera sensitivity and the correction of the optics used.
The filter has a 1.25" cell with an M28.5 × 0.6 thread. It fits accessories with a matching filter socket; the nominal cell size is not the diameter of the clear glass aperture.
• infrared cut-off while preserving the visible band
• reduction of blur and halos caused by unfocused IR
• for cameras with low UV sensitivity
• additional barrier protecting the optical train from dust
• durable coatings resistant to scratching and moisture
• filter: Astronomik IR-Block 1.25" filter
• protective filter box
• manufacturer: Astronomik
• manufacturer product code: 10230125
• type: infrared-blocking filter
• typical in-band transmission: 97–99%
• ultraviolet blocking: not a substitute for a UV-IR Block filter
• focal ratio range: all focal ratios according to the manufacturer
• cell size: 1.25"
• thread: M28.5 × 0.6
• glass thickness: 1 mm
• material: finely polished optical glass
• optical quality: diffraction-limited
• coating resistance: to scratching, moisture and ageing
• parfocality: with standard Astronomik filters using 1 mm glass
Illustration of the effect of UV/IR filtration on star image size, retained from the earlier description (credit: Carl Björk, ZWO ASI group, Facebook). It is not a measurement of the Astronomik IR-Block response and does not imply that this model provides full UV cut-off.
A correctly selected IR-Block helps produce sharper planetary data without unwanted infrared contamination.
