About this product
Part Number: CT-27009-1.25M
Premium quality 3nm SII Narrowband Filter. Chroma has made a set of Ha, OIII and SII 3nm that are optimised for F/3 beams by moving the centre wavelength slightly into the red so they will shift to the blue when used in an F/3 beam
Chroma SII filters isolate the spectral emission of singly ionised sulfur atoms, also common in nebulae. Emission is at two lines occurring as a doublet, at 671.6 and 673.1 nm. This filter also separates sulfur emission from H-alpha emission (656.3nm).
Chroma Technology is an employee-owned company based in Vermont, USA. Chroma manufacture the highest quality astronomy filters with durable, sputtered hard coatings using single substrates of the best glass, eliminating the need for laminations. All primary filter coatings are applied on the front surface and anti-reflection coatings on the rear surface to prevent ghosting and to maximise transmission. Chroma astronomical filters are used worldwide in research and amateur applications.
Highly precise and accurate, the passbands of these filters remain spectrally stable and do not drift in response to extreme temperature fluctuations or changes in humidity.
- CWL: 672.4nm, Bandwidth: 3nm
- Durable sputter coatings
- Parallelism: <30 arcsec
- Thickness: 3.0 +/-0.05mm
- Filters designed for use with CCD and for f/4.0 or slower
- Transmitted wavefront better than 0.25 waves/inch
- No reflections leading to image distortions or ‘back reflections’
Cleaning and Handling
Handle coated pieces by the edges only. Clean gently only if necessary. Loose particles should be removed with a bulb puffer or filtered, pressurised air cleaner. If necessary, gently wipe surface using anhydrous alcohol and lint-free lab towels. Use new surface of towel with each wipe.
- AVOID TOUCHING OR WIPING A/R COATED OR METAL MIRROR SURFACES
- AVOID HANDLING EXPOSED COATINGS WITH BARE FINGERS
Proper orientation of the filter is necessary in order to minimise autofluorescence and maximise performance. There is a caret (arrow) located on the edge of each filter in order to aid orientation. Excitation (x) filters should be positioned with the arrow pointing toward the specimen, toward the inside of the cube, and away from the light source. Emission (m) filters should be placed with the arrow pointing toward the specimen, toward the inside of the cube, and away from the detector/eye. Dichroic mirrors should be mounted with the coated surface toward the light source, excitation filters, and the specimen. The dichroics either have an arrow on the side pointing to the coated side, or they are beveled on the coated side. The beveled side is the smaller surface.
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