Astronomik CLS-CCD XT Clip-Filter EOS APS-C (Astronomik, SKU: 10203083) is a light-pollution filter with integrated infrared blocking. It increases the contrast of deep-sky objects against the background and can be used with cameras that lack their own IR-cut filter.
The filter suppresses sodium and mercury lamp emission lines while retaining bands containing H-beta, OIII and H-alpha. It is broader than UHC and therefore dims stars less. It can serve as a luminance filter for emission-line objects. Despite the CCD designation, it is also suitable for CMOS sensors; colour balance depends on the camera and requires calibration.
The XT version uses a very thin substrate to reduce additional aberrations at the frame edges with wide-angle lenses. Parfocality with standard filters using 1 mm glass should not be assumed; check focus after changing the filter.
The Clip mount places the filter inside a compatible camera body, in front of the sensor. This allows the same filter to be used with different compatible lenses or a telescope and reduces dust settling on the sensor. The correct version must be selected for both the camera model and the lens.
Original Canon EF-S lenses are incompatible with the EOS APS-C filter installed. The filter works with suitable EF lenses and T2/M42 adapters. It can also be fitted inside the original Canon EF–EOS M adapter for EOS M cameras; this is different from direct EOS M filter mounting.
• integrated IR blocking for cameras without their own infrared cut-off
• suppression of sodium and mercury lighting emission lines
• broader passbands than UHC, with less stellar dimming
• can record luminance data for emission-line objects
• mounting inside a compatible camera, in front of the sensor
• durable coatings resistant to scratching and moisture
• thin XT substrate for use with wide-angle lenses
• filter: Astronomik CLS-CCD XT Clip-Filter EOS APS-C
• protective filter box
• manufacturer: Astronomik
• manufacturer product code: 10203083
• transmission bands: 450–520 nm and 640–690 nm
• transmission: 95% at 486 nm, 496 nm and 501 nm; 97% at 656 nm
• infrared blocking: integrated
• focal ratio range: f/1.8–f/15
• mount: Clip-Filter EOS APS-C
• compatible APS-C DSLR bodies: Canon EOS 7D, 7D Mark II, 20D, 20Da, 30D, 40D, 50D, 60D, 60Da, 70D, 77D, 80D, 90D, 100D, 200D, 250D, 300D, 350D, 400D, 450D, 500D, 550D, 600D, 650D, 700D, 750D, 760D, 800D, 850D, 1000D, 1100D, 1200D, 1300D, 1500D, 2000D, 3000D, 4000D
• incompatible: original Canon EF-S lenses; full-frame bodies and EOS-1D
• substrate: very thin, XT version
• material: finely polished optical glass
• optical quality: diffraction-limited
• coating resistance: to scratching, moisture and ageing
Combining light-pollution suppression with IR blocking simplifies filter selection for an astronomical camera.
