Pinholes etc. (1 Viewer)

I collect holes in bits of plastic. I have ones varying from about 2mm to 8mm.
I use these for testing my eyes, my pupil size, and optics.

Firstly, where in the U.K. can one buy a set of accurate holes from 1mm or preferably 0.1mm to 8mm?

Today I got a £20 note, which for some reason has ten holes randomly from 0.1mm to 0.3mm. Who put them there I don't know.
An expensive test rig, but I can always spend it.

I noticed recently a probable small cataract in one eye when using sub millimetre holes.
It is tadpole shaped, and from the holes in the banknote it seems to measure 0.05mm across equivalent. It is not central, so I don't notice it when observing and anyway my pupil opens to about 5.5mm.

In the other eye there may be a very small cataract 0.03mm across.

With a 75mm scope, one would need 1,750x and 2,500x for these size exit pupils.

I don't know what size cataracts an optician considers relevant.
And these may not be cataracts, but they appear as tiny black spots with very small holes.

These are in the US, but I doubt there would be any trouble getting them to the UK. I hope this helps:
http://www.edmundoptics.com/optomechanics/irises-apertures/pinholes-slits/precision-pinholes/1794/
http://www.nationalaperture.com/pinhole.htm
http://www.lenoxlaser.com/index.php?dispatch=pages.view&page_id=35
https://www.pinholeresource.com/index.php/all-products/pinhole-set-detail
https://aupremierplan.fr/set-of-all-5-pinhole-aperture-sizes-now-available/

Wow!

Those little buggers are a mite pricey, aren't they?

In my former life (work) I used apertures from the French company, Melles Griot.

I wonder if you are seeing cataracts or floaters. I am certain that as a sky observer you are familiar with floaters but for the sake of completeness, floaters are particles of detached retina suspended in the ocular fluid, which, as I understand, is a gel. When observing a bright planet, say, at small exit apertures, floaters become evident because they block an appreciable portion of light, and can be distinguished by taking a second or two, after the eye is set into alignment, to come to rest, presumably due to the time lag of the gel to reach final position.

The cure for floaters can be a delightful challenge to the astronomy buff--get a big assed telescope that goes to 500x with a 1mm exit pupil! The cure for cataracts ain't no fun at all, on the other hand, but hey, insurance pays for it.

Ron

I just placed a piece of kitchen foil on a cutting board and stabbed it a few times with a fine sewing needle. 50 to 500 micron diameters were straight forward. Small were tricky but doable with patience. My magnified measuring slide (posh linen tester) was fine to check symetry and approximate dimensions.

Never tried it for cateracts. Do I want to know??

David

Maljunulo said:

Wow!

Those little buggers are a mite pricey, aren't they?

Click to expand...

Yes, they are very pricey, but they are for laser (and made by) and other high precision uses. I didn't know what sort of precision the OP was looking for.

Here's a more down to earth conversion of small drill bits and needles that may be more to the point (pun intended):
http://web.stanford.edu/~cpatton/ip-ph.html

I wonder how a zone plate would work for this application......
Again, I hope this is helpful for you.

Hi Ron and others,
Thank you.
I don't have many floaters, and I know what these are.

I sold my 520mm aperture scope a few years ago. The mirror was amazingly 1/20 wave and was made by probably the best current U.K. maker. I thanked him recently and said I didn't deserve it as I had not paid for that accuracy. But that is what he made.
I think he made an f/0.3 ellipsoid mirror professionally. Good fun.

The tiny black spots are constant over the last few months. They are only seen with tiny exit pupils if I look off centre.
I asked my optician a couple of years ago if I had cataracts, and he said no.
He said keep doing what you are doing as my eyes are fine unless tired. I.e eat lots of greens.

Last time I said 'How are my cataracts' and he said not important, so it may be I'll live my life out without having anything done. I don't know. I don't have to pay for T.V. any more, although most is not worth watching.

I don't need the pinholes etc. but they would be nice to have and especially holes from 1mm to 8mm in 0.5mm steps or better.
And I have ten pinholes in the £20 note.

P.S.
David. Do you want to know?
Not really.

Binastro said:

I don't need the pinholes etc. but they would be nice to have and especially holes from 1mm to 8mm in 0.5mm steps or better.

P.S.
David. Do you want to know?
Not really.

Click to expand...

The machine shops I know have high precision drills in exactly those sizes. Talk nicely to the chaps and I wouldn't be surprised if they'd drill a stip of aluminium for you for nothing. Or maybe a neighbour with a pillar drill might be sufficient?

The notion of someone taking a scalpel to my eyes gives me the shudders. I prefer not to think about it till I have to.

David

Hi David,

I might ask my friend for Waterhouse stops from his old camera spares.
I could use an iris from an old camera, but they move and are not reliable.

A person who represents himself in Court as a lawyer has a fool for a client.
The same applies to ones eyes.

For older people eye tests are free, at least in England.
Every two years and then every year.
One should use this service, especially if you have a skilled and wise optometrist.