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Old 06-09-2019, 08:55 AM
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Merlin66 (Ken)
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Scratch and Dig optical specs??

The scratch and Dig specs are usually mentioned "Scratch and Dig 60/40"
What does this mean to quality performing optics???
Read on:
https://www.photonics.com/Articles/U...l_Guide/a57165

I wonder where the "Super Polish" surface would measure????
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Old 06-09-2019, 12:25 PM
Wavytone (Nick)
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Scratch & dig specs are expressed as two numbers SSS/DD where SSS is the maximum scratch width, in decimal mm, and DD is the maximum depth also in decimal mm.

For example 120/20 means scratch widths not exceeding 0.120 mm and depth not exceeding 0.20 mm.

Items that fail the test may well finish up at SurplusShed or similar.

While a surface may look well polished to the naked eye, under a microscope it’s a whole different story.

Shining a laser through the glass will also highlight scratches.

One application where these numbers really matter is laser optics, where scratches will cause really bad scattering and with intense beams an imperfection will cause localise heating in the glass and quite likely damage the glass.

For telescopes it really only influences the scattered light ie extreme contrast could be compromised, if say you were hoping to spot Rigels companion star.

“Super polish” is meaningless.
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Old 06-09-2019, 01:45 PM
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Merlin66 (Ken)
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Google "coronograph polish quality" for notes and discussions on "Super Polishing"
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Old 06-09-2019, 02:31 PM
Wavytone (Nick)
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Well.. beggars can’t be choosers.

Nor can we when buying consumer-grade mass produced products.

That kind of choice only begins to be possible on low-volume artisan products where low-price is not the primary consideration.

There’s another solution too - before observing, apply an oil or wax that fills scratches and pits. Was standard practice at some solar observatories.
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Old 06-09-2019, 02:38 PM
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Slawomir (Suavi)
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Excuse me Nick, but I am a superb example of a fine Polish lad, hence one could call me a Super Polish, therefore such phrase is not meaningless
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Old 06-09-2019, 03:31 PM
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Quote:
Originally Posted by Slawomir View Post
Excuse me Nick, but I am a superb example of a fine Polish lad, hence one could call me a Super Polish, therefore such phrase is not meaningless
Yeah, I do believe you are polishing SOMETHING Suavi...
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Old 06-09-2019, 04:05 PM
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Merlin66 (Ken)
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Just thinking of the high end green stripe eyepieces and some of the latest "high end" refractors....maybe they are "Super polished"????
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