Lacerta 1.25" Herschel Prism with T2 connection

LACERTA Herschel Prism with Brewster´s angle, with 30 mm prism and shield (made in EU), T2 connection at both ends, without further accessories

Lacerta Herschel prisms allow for white light observation and photography of the sun. Herschel prisms are intended for the use with refractor telescopes. These telescopes must not have a built-in corrector. Due to the relatively high light transmission of 8%, you need an ND3 neutral density filter and a polarizing filter for visual observation.

Please note: Herschel prisms must not be used on Petzval systems or other telescopes that have glass in the optical path near the focal point. Multi-lens systems do not pose a problem as long as all optics are only at the front of the objective.


The advantages of Brewster´s angle:

The implemented Brewster angle allows for almost 100% polarization. With this, an ND3 neutral density filter and a polarizing filter, you can achieve an optimal brightness adaption for best possible perception of granules and the structures around sunspots (penumbra).

As the light of the Herschel wedge is already polarized, a single polarizing filter, screwed into the eyepiece or camera adapter, is sufficient. You can change the brigthness simply by turning the eyepiece or camera adapter).

How to use the Herschel prism:

The polarisation filter and the ND3 filter are screwed into the eyepiece or camera adapter.

The brightness is adjusted by turning the eyepiece or camera adapter.

The sequence is always: telescope, Herschel prism, filters, eyepiece or camera - the filters must not be inserted between telescope and Herschel prism.

The high degree of polarization of the Brewster angle:
The photography at left shows a comparison between Lacerta Herschel prisms (top row) and other 90° Herschel prisms. The far better change in brightness, achieved through 100% polarization, is obvious. With other prisms, you might have to use a further neutral filter to achieve a comparable effect.


For working with a Herschel prism, an ND3 grey filter is obligatory. For visual observation, you even need the polarization filter. Both filters can be found in the accessory recommendations. With the Baader Solar Continuum filter for example, which can also be found there, you can increase the contrast.