Double Stack: Each SolarMax telescope is also available with a Double Stack. This means that two Etalon filters are installed, one behind the other. This reduces FWHM of the transmitted H-alpha line light to less than 0.5 Angstroms. Without a double stack, the FWHM is below 0.7 angstroms.
The smaller FWHM means noticeably higher contrast. The structures on the sun appear three-dimensional. The narrower FWHM of the filter also means the image is darker and requires fine readjustment using with the systems tuning system.
This etalon filter allows you to retrofit your SolarMax telescope with a second H-alpha filter (known as 'double-stacking'). The etalon is simply screwed onto the lens. With a SolarMax II telescope, you will need the matching adapter ring from the recommended accessories. Like the telescope's built-in filter, this etalon is also equipped with the RichView system, which allows fine tuning of the filter. An etalon filter must never be used without a blocking filter! But of course the blocking filter is already built-in to the SolarMax telescope.
RichView™ tuning: The Doppler effect causes the wavelengths of interesting structures to vary around the H-alpha line of 656.3 nanometers. This effect is particularly noticeable in the change between the central solar disk and the edge (prominences). The RichView™ tuning system allows you to adjust the filter, to find the best possible contrast.