105 replies to this topic

[RLK1]

Regarding transmission values, I found it interesting that Ernest noted a uniform 97% transmission value for RGB in the  25mm Vixen NPL plossl eyepiece. The Svbony spl plossl is reportedly the same eyepiece with a different eyecup but I have the latter and I find it and the 30mm in the same series to perform quite well with my binoviewer. 

[j.gardavsky]

Illuminating! 

Any info on methodology?

These are the Konrad Horn's transmissivity measurements of the eyepieces, used for the astronomy, and still the reference.

 

The transmissivity numbers have been put into a colored table by some hobby staronomers group in NW Germany)*, and they have expressed their thanks to APM for providing the data, otherwise free on the web by astrovox.

 

The transissivity measurement standard has been defined by PTB (Physikalisch-Technische Bundesanstalt in Braunschweig), which is a counterpart of ISO for Germany.

 

Clear skies through the clear eyepieces,

JG

 

)* I forgot who were these people, but I don't remember everything.

[Highburymark]

Intresting

Eyepieces transmissivity astrovox.pdf

Despite having lots of microscope options at 25mm, these transmission figures show why I’ve always kept pairs of TV Plossls at 32mm, 20mm, 15mm and 11mm. Their performance remains unsurpassed for solar Ha binoviewing, when brightness is crucial, particularly at higher powers. If pushed, I would choose them even over Tak Abbés and TPLs for solar - they just seem to have an extra something.

[davidgmd]

These are the Konrad Horn's transmissivity measurements of the eyepieces, used for the astronomy, and still the reference.

 

The transmissivity numbers have been put into a colored table by some hobby staronomers group in NW Germany)*, and they have expressed their thanks to APM for providing the data, otherwise free on the web by astrovox.

 

The transissivity measurement standard has been defined by PTB (Physikalisch-Technische Bundesanstalt in Braunschweig), which is a counterpart of ISO for Germany.

 

Clear skies through the clear eyepieces,

JG

 

)* I forgot who were these people, but I don't remember everything.

  
Thanks Jiri. I was curious if they measured a single sample or multiple examples of each eyepiece. And if multiple, what sort of standard deviation did they observe. My guess (hope) is that there would be very little difference between samples of the same eyepiece.

  
Also, do you know if scatter and transmission are related? Will a lens or eyepiece with more scatter necessarily have lower transmission, or are the two independent of each other?

Edited by davidgmd, 12 April 2025 - 05:25 PM.

[Procyon]

Here's one more I had stowed away somewhere. Actually many are from here it seems: https://astro-talks....?p=54992#p54992

 

 Newsoft Excel Worksheet (2).xlsx   13.82KB   8 downloads

 

Still waiting for TOMDEY to publish his great findings in a book. 

 

Edited by Procyon, 12 April 2025 - 10:17 AM.

[j.gardavsky]

  
Thanks John. I was curious if they measured a single sample or multiple examples of each eyepiece. And if multiple, what sort of standard deviation did they observe. My guess (hope) is that there would be very little difference between samples of the same eyepiece.

  
Also, do you know if scatter and transmission are related? Will a lens or eyepiece with more scatter necessarily have lower transmission, or are the two independent of each other?

Hi David,

 

I have no ther details to the Konrad Horn's measurements, and the links to his laboratory went somehow lost.

 

Scatter and transmission are related, more scatter, less transmission into the exit pupil when the eyepiece is mounted afocally on a telescope.

 

The Zeiss (Pl, E-Pl, W-Pl, S-Pl), and the Leica HC and L eyepieces differ from most of the other eyepiece in:

1. Nearly zero visible scattering and reflection on the multicoated glass-to air and air-to glass lenses surfaces on the lenses inside the eyepece.

2. Zero visible scattering and reflection on the contact surfaces of the lenses doublets (and triplets).

3. Low scattering on the microinclussions in glass.

 

What is basically left is the scattering on the outer glass surfaces- to- air on the field and eye lenses, where the multicoatings have added protective hard layer against scratch.

 

Best,

JG