3/26/2023 0 Comments Build your own sun spotter![]() ![]() One design, produced by DayStar Filters of California, is a multi-component interference filter using as its core a Fabry-Perot etalon. For viewing fine chromospheric disk detail, a more complex high quality sub-angstrom bandwidth filter is usually needed. For better prominence viewing, much more expensive Coronagraph-type viewers are available which use solar occulting disks coupled with a narrow bandpass filter and high-quality optics. It is suitable mainly for viewing limb prominences, sunspots, and very bright major flares, since the filter does not have the sharp-edged sub-Angstrom passband needed for revealing much chromospheric disk detail. One design, produced by Lumicon (2111 Research Drive, #5S, Livermore, California 94550), is a 1.5 Angstrom FWHM (Full Width at Half Maximum) Prominence filter, using multi-layer dielectric coatings on a glass surface similar to their nebular filter designs. The other method of H-alpha viewing involves a special narrow band filter. ![]() For those interested in building one, the basic details are described in the January 1969 issue of Sky and Telescope magazine. It is rather bulky, and thus is used mainly in a heliostat-fed horizontal solar telescope. The instrument has the advantage of rapid tunability not only around H-alpha, but in other spectral lines which show emission, such as the K-line of Calcium. One method of doing this involves using a spectrohelioscope, an image-scanning spectroscope using pairs of moving slits to allow monochomatic viewing of the sun. H-ALPHA FILTERING SYSTEMS: Unlike continuum “white light” observations of the sun, observing the chromosphere requires a very narrow bandwidth filter centered on the Hydrogen Alpha spectral line (6562.8 Angstroms), which not only reduces the intensity of the sunlight to a safe level, but eliminates much of the photosphere’s contribution to the image.
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