This set consists of an H-alpha etalon with half-width of less than 0.7 angstroms and a blocking filter built-in to a prism star diagonal.
This combination allows you to convert your refractor (lens telescope) into an instrument which you can use to safely observe the Sun in H-alpha-light. The H-alpha line, at a wavelength of 656 nanometres, allows you to observe the Sun's chromosphere - i.e. the atmospheric layer above the solar photosphere. Observe prominences, filaments and other changeable phenomena. There is always something going on in the H-alpha light on the Sun!
Please note - safe use is only possible with the combination of etalon and blocking filter. No single part on its own is sufficient as a filter! Two specifications are essential for selecting these solar filters - the first number in the product name represents the diameter of the etalon and the second the diameter of the blocking filter.
BF blocking filter: The deflection optics with the eyepiece receiver also accommodate the blocking filter. This filter reduces the brightness of the solar image and is therefore a very important part of the solar telescope, and which must under no circumstances be removed!
The number after the BF in the product name indicates the diameter of the blocking filter in millimetres. For example, BF10 means that the blocking filter is 10 millimeters in diameter. For purely visual observing, a small blocking filter is sufficient, but for photography a larger one should be selected.
The size of the blocking filter should be chosen so that the entire solar disk can be seen. The longer the focal length of the telescope, the larger the solar image and thus a larger blocking filter will be required. You can see the recommended focal length for this set in the technical data.
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.