Optical flats?

[inapottingshed]

I have a small mark on a CCD sensor that won't come out with light polishing. Someone mentioned to try optical flats... What would I need - presumably some 'optical flats' and some kind of optical 'grinding paste'?

[SteveL]

EEEEEEEEEEEEEEEKKKK!!! lol! Sorry, not even close, but it did scare and amuse me in equal measure....

"Optical flats" are a set of image taken against an evenly illuminated surface, and exposed so the average level in the image is about 1/3 to 1/2 of full level. These are then used to remove vignetting, dust bunnies, and any other optical inperfections in your imaging train.

[steppenwolf]

Actually, Inapottingshed and SteveL are both right, an optical flat is indeed an object, to quote:-

"Optical flats are optical-grade glass structures lapped and polished to be extremely flat on one or both sides, usually within a few millionths of an inch."

However the advice you have been given is as per Steve's explanation which is to take 'FLATS' to calibrate your images and thus 'cancel out' the blemish.

[PeterW]

Repolishing you CCD could erode any anti-reflection coatings on it or even wear into the actual structure of the device. DO NOT GO THERE!

The only cleaning I would recommend is very gentle wiping with a lint free wipe and isopropanol.... works for proper optical surfaces.

Cheers

PEterW