 |
| TLAPO80/480 with Lacerta Herschel Wedge and ASI290MM |
Some information about my new Lacerta Herschel Wedge. According reviews a Herschel wedge or Herschel Prism would provide more details then the use of Solar film.
My objective is to get more details of the photosphere and the more specific on the granulation itself. Another objective is to use the wedge with my Sol'Ex.
The Herschel Wedge is equipped with a neutral density filter ND3. On the back of the wedge it's noted that the total light reduction with ND3 filter us ND4.07.
This means that the wedge itself has a light reduction of 4.07 - 3 = ND1.07 . For both visual and photografic observation a value of ND1.07 is too low and even dangerous. To compare with my Solar film ND3.8 I would need to install a filter ND2.7 or ND2.8. on the wedge. But for now I will keep using the ND3filter.
A value of ND1.07 means a transmission of : T= 10 exp (-ND) = 10 exp (-1.07) = 0.0851 or 8.51%.
Another interesting one is Brewster Angle.The Brewster angle, named after the Scottish physicist Sir David Brewster, is the angle at which the reflected light rays from a non-metallic surface are fully polarized. In other words, the light waves that strike a surface at the Brewster angle are reflected in only one specific direction (polarized light), while the perpendicular light waves are absorbed.
The Brewster angle can be calculated with the following formula:
tan(θB)=n2/n1
where θB is the Brewster angle,
n1 is the refractive index of the medium from which the light comes (e.g., air),
n2 is the refractive index of the medium in which the light is reflected (e.g., glass or water).
At the Brewster angle, the resulting reflection of light for a particular polarization direction is minimal, which can be useful in various optical applications such as my use of the Sol'Ex.
Air typically has a refractive index of approximately 1 (as an approximation), while the refractive index of glass (like in the Lacerta Herschel wedge) is typically between 1.4 and 1.6, depending on the type of glass.
Let's assume a refractive index of 1 for air and a refractive index of 1.5 for glass for simplicity. So, in this example, the Brewster angle for air and glass is approximately 56.31. According the website the Brewster Angle is 56.6°.
Above picture is taken with TLAPO80/480 f/6, ASI290MM and Herschel Wedge. Editing using new beta release of IMPPG and CS4 after stacking with AstroSurface Urania V1.
