4 replies to this topic

[tcalderw]

A while ago a found an online vendor offering a neutral density filter implemented as thin metal with tiny holes.  I now cannot locate this vendor.  Has anyone seen something like this or know what such a filter is properly called?

 

Tom

 

PS: The application here is single-channel photometry

Edited by tcalderw, 13 April 2025 - 05:10 PM.

[cuzimthedad]

Moving to Eyepieces...

[azure1961p]

Yes if I've got it right the multitudes of micro holes act like so many apertures.  They've even made full size sunglasses with this method, said to improve vision due to the extended focal ratio from so many indidual micro apertures. It's a novel thing know doubt. Never looked through one but I get the way it works.  Probably reduces astigmatism too.

 

Pete

[Ernest_SPB]

There are so named "random pinhole attenuators" for laser beam. They can be used like ND filters with no influence to the light spectrum. I had no relations to the filter usage, but I am sure they must produce a lot of light scatter - hardly ever applicable to astronomic devices  

Edited by Ernest_SPB, 14 April 2025 - 01:10 AM.

[triplemon]

Yes if I've got it right the multitudes of micro holes act like so many apertures.  They've even made full size sunglasses with this method, said to improve vision due to the extended focal ratio from so many indidual micro apertures.

If your pupil allows light from more than one such micro aperture at a time and still combines it into a single point on your retina, your effective focal ratio and any focusing issues associated with it won't change. Consider it a bit like a multi-mirror telescope or an radio antenna phased array.