laser ray tracing the zenith prisms

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j.gardavsky Germany
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laser ray tracing the zenith prisms

#1

Post by j.gardavsky »


Hello all,

as there has been recently criticized the "mud" in the Takahashi 1.25" zenith prism,
tak prism mud.jpg
I became a bit more curious.

The next pic shows a laser beam tracing through:
1. Wild Heerbrugg (Switzerland) 60mm prism with the silver coated diagonal and multicoated faces, and
2. Takahashi (Japan) 1.25" prism, uncoated and with the total internal reflection
Laser Ray Tracing Through The Prisms.jpg
The difference is well recognizable.

Thank you for looking,
JG

PS: It makes sense to click on the 2nd pic to see better the difference between the Wild and the Tak technologies.
6" F/5 Sky-Watcher achro, 2" BBHS Star Diagonal, 2" zenith prism, 1.25" Takahashi prism
Leica 82mm APO Televid
Eyepieces: Docter UWA; Leica B WW and WW Asph. Zoom; Leica HC Plan S and L, monocentric; Pentax SMC XW, O-, XO; Tak MC O, Carl Zeiss B WW, and Pl, E-Pl, S-Pl, W-Pl;
Swarovski SW; Baader Symmetric Diascope Edition; Nikon NAV SW, ; TMB supermonocentric; Rodenstock; Vixen HR; TV Delos
Filters: Astrodon, Astronomik, Baader, Balzers, Zeiss West and East, Lumicon
Binoculars (7x42 up to 15x85): Docter Nobilem, Leica Ultravid, Nikon Astroluxe, Swarovski EL Swarovision; BA8 (Kunming Optical)
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NGC 1365 Australia
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Re: laser ray tracing the zenith prisms

#2

Post by NGC 1365 »


Tell us more, what was the issue with the Tak Prism, I have 2 and they see to work okay.
Ivan
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Re: laser ray tracing the zenith prisms

#3

Post by j.gardavsky »


Hello Ivan,

the problem has been reported on Cloudy Nights in https://www.cloudynights.com/topic/7642 ... -be-right/
It is less visible on my sample.

The other problem I have found, are the horrible internal reflections, as documented in the OP above.

Highly likely, the prisms don't come from the Takahashi OEM production, but they may get just the Takahashi label.

Best,
JG
6" F/5 Sky-Watcher achro, 2" BBHS Star Diagonal, 2" zenith prism, 1.25" Takahashi prism
Leica 82mm APO Televid
Eyepieces: Docter UWA; Leica B WW and WW Asph. Zoom; Leica HC Plan S and L, monocentric; Pentax SMC XW, O-, XO; Tak MC O, Carl Zeiss B WW, and Pl, E-Pl, S-Pl, W-Pl;
Swarovski SW; Baader Symmetric Diascope Edition; Nikon NAV SW, ; TMB supermonocentric; Rodenstock; Vixen HR; TV Delos
Filters: Astrodon, Astronomik, Baader, Balzers, Zeiss West and East, Lumicon
Binoculars (7x42 up to 15x85): Docter Nobilem, Leica Ultravid, Nikon Astroluxe, Swarovski EL Swarovision; BA8 (Kunming Optical)
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Re: laser ray tracing the zenith prisms

#4

Post by NGC 1365 »


Thanks JG, do you notice much difference on the moon. I use mine mostly for lunar and see very little, if any glare or ghosting, and both prisms perform the same. The Baader 1.25" prism diagonal I have shows noticeably more.
Thanks
Ivan
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Re: laser ray tracing the zenith prisms

#5

Post by j.gardavsky »


Hello Ivan,

as soon as possible, I will run a comparison between the Tak and Wild prisms on the terrestrial objects and on the Moon.
At the moment we are locked down by the cloudy weather.
The Tak is my first prism from Asia-Pacific, and actually purchased because of my curiosity, not because I would need it.

In Germany, we are more inclined to repurpose the big Rodenstock or Wild Heerbrugg prisms for the astronomy telescopes, and there used to be shops making these repurposings, like Manfred Pieper,
https://www.ebay.de/itm/133731543117?ha ... SwgOhgbKbK
And this may be the case when somebody needs a big prism for his/her 3" eyepiece.

The md-optics in Berlin Wandlitz offers surplus prisms from Zeiss, some of them can be used when replacing the prisms in the binoculars.

Best,
JG
6" F/5 Sky-Watcher achro, 2" BBHS Star Diagonal, 2" zenith prism, 1.25" Takahashi prism
Leica 82mm APO Televid
Eyepieces: Docter UWA; Leica B WW and WW Asph. Zoom; Leica HC Plan S and L, monocentric; Pentax SMC XW, O-, XO; Tak MC O, Carl Zeiss B WW, and Pl, E-Pl, S-Pl, W-Pl;
Swarovski SW; Baader Symmetric Diascope Edition; Nikon NAV SW, ; TMB supermonocentric; Rodenstock; Vixen HR; TV Delos
Filters: Astrodon, Astronomik, Baader, Balzers, Zeiss West and East, Lumicon
Binoculars (7x42 up to 15x85): Docter Nobilem, Leica Ultravid, Nikon Astroluxe, Swarovski EL Swarovision; BA8 (Kunming Optical)
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Re: laser ray tracing the zenith prisms

#6

Post by Lady Fraktor »


The light scatter shown in your image above was quite surprising JG.
I would expect some better internal blackening than that.
I wonder if felt/ flocking would make a slight improvement.
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
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Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Takahashi prism, TAL, Vixen flip mirror
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Re: laser ray tracing the zenith prisms

#7

Post by j.gardavsky »


Hello Gabby,

the case with the scattered light is even worse in the pic posted by another user on the CN. It is no to as bad on my sample, but still well visible.
The scattered light on the Tak may become a problem on the fast telescopes. This is at the moment my guess.

Best,
JG
6" F/5 Sky-Watcher achro, 2" BBHS Star Diagonal, 2" zenith prism, 1.25" Takahashi prism
Leica 82mm APO Televid
Eyepieces: Docter UWA; Leica B WW and WW Asph. Zoom; Leica HC Plan S and L, monocentric; Pentax SMC XW, O-, XO; Tak MC O, Carl Zeiss B WW, and Pl, E-Pl, S-Pl, W-Pl;
Swarovski SW; Baader Symmetric Diascope Edition; Nikon NAV SW, ; TMB supermonocentric; Rodenstock; Vixen HR; TV Delos
Filters: Astrodon, Astronomik, Baader, Balzers, Zeiss West and East, Lumicon
Binoculars (7x42 up to 15x85): Docter Nobilem, Leica Ultravid, Nikon Astroluxe, Swarovski EL Swarovision; BA8 (Kunming Optical)
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