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Herschelwedges (Solarprism) are made for the solar observation with refractors. Around 95% of the solar light will be blocked. With an variable polarising filter and strong grey filters the sunlight will be reduced to the necessary amount. Unlike objectiv solar filters the filtering happens close to the eyepiece or camera. Normaly the contrast and sharpness of the solar image with an Herschelwedge is much higher.
The advantages of the Lunt Herschelwedge:
- Perfect surfaces for a very high contrast
- Completely closed housing with integrated heat trap
- No scattered light escaping, for maximum safety
- Delivered in sturdy aluminium case with foam insert
Only for using with refractors: The full solar energy enters the telescope and the filtering happens close to the focal plane, so we only recommend refractors for the working with the Herschelwedge. Otherwise the refractor shouldn´t have a rear corrector lens. The optical elements would heated through the concentrated solar energy and could be damaged. Also filters are only allowed at the eyepiece side of the Herschelwedge and not at the front.
The advantages of Herschelwedges at refractors: In addition to the better image quality, the Herschelwedge offers more light. So you can use special contrast filter, like the Baader Solar Continuum. With filters like this you can increase the contrast at the sun.
Regulation of image brightness: Of course 5% are too much for the solar observing. So you need an additional filter for light reduction. An ND3 Filter is screwed directly in the eyepiece barrel. Because the Herschelwedge produces polarised light, you only need a simple polarising filter to screw into the eyepiece or photoadapter for additional light reduction. Now you can rotate the eyepiece and so reduce the light. With additional grey filters and the Baader Solar Continuum Filter you can reduce the brightness to the required amount and so affect the contrast.
