TSE-21WD protective window? (1 Viewer)

[4th_point]

I recently acquired a fixed 20x wide eyepiece for the System S mount and it appears to have a plain flat glass window that is fixed in place with what appears to be silicone sealant. It is on the end that goes into the scope body. I contacted Kowa and the response was that it might be "aftermarket" or something that Kowa did. It does not seem to affect the view in anyway that I can tell.

Has anyone else seen this?

It seems like a nice eyepiece but I may end up selling it, so any information would be helpful (to provide to buyer).

Thanks,

Jason

 

[Binastro]

Optical windows are sometimes used to waterproof optics.

Many binoculars have optical windows in front of the objectives.
Canon 18x50, 8x25 etc.
Minolta Mariner.

Sometimes to stop dirt entering, especially with front focus binoculars.

Also used to hold secondary mirrors on some astro scopes or to stop tube currents.
With large telescopes tilting the optical window by one degree prevents ghost images.

It is likely the Kowa eyepiece has a standard optical window, hopefully coated.
There may be another optical window at the back of the scope body.

Regards,
B.

 

[4th_point]

Thank you, Binastro.

I didn't think about the coating. I'm glad that you mentioned it. When I shine a bright LED light on the window it has a greenish reflection.

 

[Binastro]

A white Led torch with greenish reflection suggests a multicoated window, but LEDs can be more or less monochromatic.

I use an old tungsten 60 watt bulb.

I think the Kowa eyepiece is probably mostly multicoated.

B.

 

[4th_point]

Good to know. Thank you.

 

[jring]

Hi,

seems strange but stock... see Kowa TSE-21WD 20x Wide Okular | Clean Cameras | Markus Säuberli which has an image of the front element (among others)...

Joachim

 

[4th_point]

Thanks Joachim. It looks similar to mine.

I found a picture of another 20x wide that did not have that front element, but I could see the ledge or lip where the flat glass could rest.