Lacerta 1.25" Herschel Prism Set with ND3 Filter and Adapters

LACERTA Herschel Prism with Brewster´s angle, with 30 mm prism and shield (made in EU), T2 and 1.25" connection at both ends, with ND3 filter

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 still relatively high light transmission even with the ND3 filter, you need 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, the 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 set:

The ND filter is already mounted into the eyepiece-side connection adapter and allows safe observation.

The polarisation filter is 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 (with ND3 filter), 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, the built-in ND3 grey filter is obligatory. For visual observation, you still need the polarization filter. This filter 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.

Question:

1) Does this Herschel wedge have a built-in UV and IR blocking filter?
2) Does it have a dissipator (heat spreader)?
?

Answer from Teleskop-Service:

1) An IR/UV cut filter is not built in, so you can take pictures in calcium light and also in the IR range.
The blocking filters are optional, only the ND3 is always part of the Lacerta Herschel wedge sets.

2. Yes, on the back is the area for heat dissipation, recognizable by the ripples.
There is a small gap between this surface and the rest of the housing to prevent heat from transferring to the housing and causing turbulence.
For the same reason, the Lacerta Herschel wedge is the only one on the market that is open at the bottom so that no heat accumulation impairs the image.

Bonus: answer to question 3, which comes up often with "open at the bottom":
3. No, the shoes do not start to burn when using the Lacerta Herschel wedge which is open at the bottom. ;-)