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Old 11-05-2021, 09:41 PM
legswilly (Werner)
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legswilly is offline
 
Join Date: Apr 2021
Location: Wauchope, NSW, Australia
Posts: 22
[QUOTE=multiweb;1519244]You still have a sharp angled obstruction in your circular scope aperture so that statement is incorrect.



I did not think of that and you are right. I found some more information on this site https://skyandtelescope.org/wp-conte...-Secondary.pdf.


To make a flat and to test it for flatness. It is similar to scraping a cast iron table flat. It needs 3 pieces and altenative scraping with prussian blue as marker. Testing for the glass flat is with an optical flat and monochrome light.
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