Price 269,00 €
The LACERTA Herschel prisms differ from the other Herschel prisms on the market (INTES, LUNT, Scopium etc ...). They enable full polarization at the Brewster angle, in contrast to the 90-degree versions, which are easier to manufacture, where only partial polarization is possible.
Why Brewster Angle?
The Lacerta Herschel prisms with Brewster angle have some advantages over 90 degree prisms: Since the polarization at the Brewster angle (57 degrees) is almost complete, the Lacerta Herschel prism with the mandatory ND3 neutral density filter AND with an additional polar filter enables practically full light attenuation - in In reality, a dimming range between ND4.07 and 6.37 - usually even more. Without a polarizing filter, the Herschel prism works at the lowest light attenuation (ND4.07) and can thus be used for photography. With the "traditional" 90 degree Herschel prisms, this value is between 4.24 and 5.00.
The visual perception at different neutral densities is shown in the picture below. It is easy to see that the granulation in traditional Herschel prisms can only be observed well with an additional THIRD filter (ND3 and polarizing filter are required!). Herschel prisms with Brewster angle do not need an additional filter because the dimming range is continuously possible up to ND6.37!
When do you use the 2 "Herschel prism?
Below 2000mm focal length the 1.25 "prism is sufficient, and it saves the focus path that you might need for the filter adaptation. Above 2000mm focal length the 2" Herschel wedge is indicated, you need at least 130mm free focus path because of the additional structures for the filters The unit of rotation is a little more than that of a 2 "star diagonal.
How do you use the 2 "Herschel prism?
Why is the Lacerta Herschel prism open at the bottom?
NOTE! This is the M48 model!
These terms and conditions are valid from November 7th, 2020.
Astro Art Finland
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