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Old 18-10-2020, 06:28 PM
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Question Where to find plastic thin meniscus?

Gents,

For one of my next projects, I need thin (~1 mm) glass or plastic meniscus, >31 mm, radius of curvature should be close to ~105mm.
I was considering cutting the piece from safety goggles (curvature seems to be adequate), but before I try that (I am not entirely sure how to do it yet...), perhaps suitable stuff is available off the shelf?
Thanks in advance for tip off :-)
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Old 18-10-2020, 06:53 PM
JA
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Hi Bojan,

Maybe you could try something like a watch face, that would be close to that diameter, you just need to ensure that if you need it for optical properties that you stay away from its edges where the radius will tighten. I suspect that if you found a ~40mm face you should be OK to have a reasonably constant radius for the 31mm zone you need. Where = Of course try eBay or an old toy watch or something?

Good Luck
EDIT..... As an example try this in increments of various diameters from 30 to 38....
https://www.ebay.com.au/itm/1pc-30-3...sAAOSwLVFbogvH

Or find a circa 200mm diameter acrylic sphere and start cutting

Best
JA
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Old 18-10-2020, 08:17 PM
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Thanks, I will have a look at acrilyc sphere, this is good idea.. yes, curvature radius should be constant within 31 mm...
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Old 18-10-2020, 08:46 PM
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Found something good for very reasonable price..
https://www.ebay.com.au/itm/6-Inch-T...frcectupt=true

It could also be suitable for all sky camera :-)
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Old 19-10-2020, 12:57 PM
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Sounds like you have what you need, but if not, these are 31mm D and 1 mm thick:
https://www.ebay.com/itm/1-0mm-Thick...75.c101224.m-1
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Old 22-10-2020, 06:50 PM
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I decided to go this way.. low cost approach..
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Old 22-10-2020, 07:02 PM
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what's it for?
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Old 23-10-2020, 08:09 AM
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Erm.. it is exercise in frugality and "cheapness" from my side actually.

Some time ago I bought on ebay a pair of very cheap rifle sights, in hope they could be useful as RDF (I have a few of real ones, bought them for 20~30$). So I basically written off $10 I paid for the lot in question.

It turned out (not unexpectedly) that they are actually fakes.. looked (almost) like one thing but were actually something else... however still could be called "sights"..
Anyway, I decided to "repair" one of them and this is what I came up with.. The curvature of the safety goggles plate used as reflective lens in my application is about right for this frame. I will have double reflection, but that will be OK.

I still need to insert red LED in place (it will be possible to adjust focus more precisely and also I will try to implement aim adjustment, which is missing in this "product").. It seems it will work OK.
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Last edited by bojan; 24-10-2020 at 07:36 AM.
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Old 25-10-2020, 12:23 PM
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That's it...
Since it's very light, it could be used for wide fields, mounted on camera flash adapter.
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