This accessory from the QUARK series enables you to perform solar observation in the calcium H-line. Like every QUARK filter, this one simply slots into the telescope’s focuser.
Please note: The QUARK Calcium H-line solar filter should only be used in conjunction with refracting telescopes (lens telescopes) with a maximum aperture of 150 millimetres. For apertures of 80 millimetres or greater, a UV/IR-blocking filter should be used; however, this must still be transparent to light in the calcium H-line (see ‘Recommended Accessories’). The refractor should not have any optical elements positioned behind the front lens, as high temperatures occur near the focal point – as the name suggests – which could damage these elements. Therefore, please do not use any flatteners, barlow lenses or similar accessories.
The manufacturer DayStar recommends refractors with an aperture ratio of f/8 to f/15, for example:
With a longer focal length, the image becomes darker but offers greater contrast.
The two spectral lines, calcium-K (CaK) and calcium-H (CaH), are just as significant in scientific solar observation as the hydrogen H-alpha line. Both calcium lines have wavelengths of less than 400 nanometres. The sensitivity of the human eye to these wavelengths decreases noticeably with age. Filter manufacturers therefore focus on the shorter CaK wavelength and recommend purely photographic observation, as the CCD chip is sensitive enough.
The Calcium QUARK is designed for the CaH line. At 397 nanometres, this has a slightly longer wavelength than the CaK line (393 nm). According to the manufacturer, this colour is still visible to most people, meaning that the Calcium QUARK is also suitable for visual observation.
In calcium light, just as in H-alpha light, you can perform observations of the Sun’s chromosphere. The image on the right gives an impression of this. Protuberances are also visible in the light of the calcium ions. However, due to their low brightness, they are best observed photographically.
