Lacerta Herschel Wedge - Brewster Angle

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.

My Blog Statistics - Blogposts and Visits

A visual presentation of my @blogposts and #visits of my Astro Page blog. This year, blogpost number 2000 was posted. 

First light with Lacerta Herschel Wedge

The sky cleared unplanned so I could set up my mount with my new Lacerta Herschel Wedge.
With the set up I was not able to capture the entire solar disk. I tried to use my reducer but this was not succesful.

I'm not sure but the exposure time was almost at it's minimum. Need to follup this next time and for sure when the Sun climbes higher in the sky.

Setting:

TLAPO80/480 with ASI290MM

Herschel Wedge with ND3 filter

Exposure time 0.059ms, binning 1x1, 16bit, gain 0

Software: SharpCap 4.1, AstroSurface V1 Urania, IMPPG, CS4

Sunspots at the far side seen from Mars rover Perseverance

The Sun rotates on its axis once in about 27 days. This rotation can be seen by observing sunspots. This also means that Sunspots at the far side of the Sun can not be seen from Earth. With help from Helioseismology it's possible to create images of the far side and it's sunspots. Another interesting source is coming from Mars. The Mars rover Perseverance uses it's MastCam Z camera to take pictures of the Sun. Those pictures are not perfect but huge sunspots are visible and this can be interesting at the moment planet Mars is positioned towards the "far side" of the Sun.

For Mars Perseverance Images see this link.

I made a comparison between an image from the rover and the far side using helioseismology. The images are both made on December 22, 2023. We will see a week from now what it will bring.

Updates available SharpCap, APP, JSol'Ex, ASIStudio

As the year ends, I made some time to update my astrosoftware :

ASIStudio : 1.9.5

AstroPixelProcessor APP : 2.0.0 beta26
SharpCap : 4.1.11536 

JSol'Ex : 2.0.0

Still need to retest the new Stellarium and N.I.N.A. together with my EQ6.

Have fun. 

Sol'Ex Presentation at VVS Capellla Hoegaarden

At the request from astronomyclub VVS Capella Hoegaarden my collegue Walter and myself (collegue Johan was excused) gave a lecture on our project Sol'Ex. The title of the lecture was "DIY The Solar Explorer".

We arrived quite early, so early in fact that we were the first. Plenty of time to settle in and explore the place. A little later Joost, chairman of the club, arrived and treated us to a drink. The room slowly filled up and Henk ensured that online streaming could take place. The lecture could begin, a bit awkward at first, but after the first of the many questions were asked it went much more smoothly. Walter supplemented well and provided additional explanation where necessary. Ultimately, the lecture lasted an hour and a half and the feedback from those present was good. The conversations at the bar continued with satisfaction.

The online recording is available and can be viewed via this youtube link.

The presentation (PDF version) itself is available via Google Drive  via this link. 

Sol'Ex Presentation @ VVS Capella Hoegaarden

 

Together with my collegue Walter, I wll be talking our Sol'Ex project next thursday December 21, 2023 @ VVS Capella in Hoegaarden.