ALTAIR ASTRO Solar Contrast Filter G Band 2nm - 1.25" 430.3nm

Another first for solar astronomy, the Altair G-Band 2nm Solar filter enhances the finer details of the solar photosphere. Contrast is enhanced, improving the visibility of faculae against the photosphere and between the threshold and penumbral features of a sunspot. Visible structural details within sunspots and their immediate surroundings are improved. The convection cells of the photosphere, also known as "granulation", have also been enhanced, as has an image of the entire solar disk with Altair's G-band filter (opens a new window). Shown here is a high-resolution image with the Altair G-band filter and a 300 mm Newtonian telescope (new window).

This filter also poses an interesting challenge for solar imagers: In addition to enhancing contrast, the G-band filter can also reveal the elusive "bright spots" between solar convection cells with a 250 mm aperture reflector or larger. Amateurs do not usually obtain images of these difficult structures, but they are now within reach. This would require Baader ND3.8 solar film suitable for imaging. Newtonian telescopes and classic Cassegrains are ideal for such applications. Please ask us about custom-made large solar filters.

Note: This filter is designed to be used with a professional and safe glare reduction filter, such as Baader solar film filters (reflectors and refractors) or the Altair Imaging-Ready Herschel Wedge (refractors only). The Baader "photographic" solar film would be slightly better, however normal film, or filters would also work well due to the super high transmission of ~96%.

Each filter is supplied with a high resolution spectrographic analysis, unique to that particular filter serial number.

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

UV, IR and visual wavelengths are blocked, and only an ultra-narrow blue FHWM band from 2nm to 430.3nm is transmitted to your camera. This greatly increases the contrast of solar features when observed or imaged with a color or mono camera, revealing more detail in the solar photosphere.

A mono camera is recommended, such as the superfast Altair Hypercam 174M or the ultra-fast Altair GPCAM3 287M Mono USB3 Camera (AKA "Babyshark").

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 the Altair GPCAM or any other 1.25" nosepiece. For a Hypercam with 2" revolver you can order a 1.25" revolver or use an Altair magnetic filter holder with 1.25" filter slider and choose the correct thread for your camera.

Technical Specifications:

• Standard 1.25" filter with threaded aluminum cell
• CWL 430.3nm @ 96% transmission, 1% tolerance.
• FWHM 2nm, tolerance 0.5nm.
• 1.85mm thick λ/4 quartz, Parallelism (arcsec) 30
• Si02 "hard" coating with UVIR blocking 300-1100nm and anti-reflection coating
• High resolution spectrographic test report is included for each individual filter.
• Altair Astro and its distributors reserve the right to change product specifications and pricing without prior notice.