ALTAIR F200SCB5408 solar contrast amplifying filter, 8nm and 540 nm, 2" continuous

The Altair 2" Solar Continuum filter enhances sunspots, graininess and fine details of the photosphere. For use with the Baader solar filter or the Herschel wedge filter.

IMPORTANT SAFETY INFORMATION: DO NOT USE THIS FILTER FOR DIRECT SOLAR OBSERVATION! It must be used in conjunction with a professional solar filter or Hershel wedge filter with a maximum transmission of 0.024% placed BEFORE this filter. For reflecting telescopes, we recommend placing a Baader solar film on the front of the telescope and then screwing the filter into a filter holder, camera or eyepiece. For refractors, the filter should be placed just in front of the camera or eyepiece with a Hershel wedge filter attached. Do not use this filter without a proper solar pre-filter in place, as it will permanently damage your eyes or camera!

The solar contrast amplifier works by filtering out ultraviolet, infrared and visual wavelengths except for a narrow green band of 8 nm FHWM at 540 nm. This greatly increases the contrast of solar features when viewed with the naked eye, color or monochrome camera, revealing more detail around sunspots and granulation (rapidly developing solar convection cells) in the solar photosphere.

Highly recommended for use with Altair Imaging-Ready Hershel wedge or Baader solar film. NOTE: Do not insert the filter before your Hershel prism or it will melt, it must be placed right in front of the camera and screwed directly into your camera's 2" revolver using the M48x0.75mm thread, e.g. Hypercam's 2" revolver or use an Altair magnetic filter holder with 2" filter slider and choose the correct threads for your camera.

why does the transmission focus on the 540 nm wavelength?

540 nm is a very desirable wavelength for imaging and observing the sun. The Solar Contrast Booster filter improves the performance of any telescope optics, such as refractors, Newtonian reflectors, Maksutov, Dall Kirkham, Cassegrain and SCT.

It is especially recommended with Frauenhofer achromatic refractors and short focal length ED doublets, because their optimum performance peaks at this green wavelength by design. In fact, not only achromatics, but also most ED and APO triplet refractors traditionally have peak performance at the 540 nm wavelength, where the human eye shows its best sensitivity. 530-540 nm is not only the traditional "design reference wavelength" for most telescope optics, but also that of most high-end interferometry equipment used to configure and optimize telescope lenses.

most color and monochrome CMOS cameras also have maximum sensitivity and resolution in green! Color CMOS cameras, in particular, have an RGGB pixel arrangement with two green pixels for every blue and red pixel, which is an obvious increase in resolution. Therefore, there are many advantages to isolating this wavelength to capture those fleeting moments of good vision.

Technical Specifications

• Aluminum cell filter with standard 2" screw thread
• CWL540nm band 90% transmission FWHM 8nm
• 1.85mm thick λ/4 optical glass, parallelism (arcseconds) 30"
• Si02 "hard" coating with UVIR blocking 300-1100 nm and anti-reflective coating