Jump to content

Banner.jpg.b89429c566825f6ab32bcafbada449c9.jpg

Stains?.


Recommended Posts

Bresser 10 inch Dob, I have just noticed stains on the end of the scope, on the part which looks like an alloy plate, where you adjust collimation etc., is this normal, or does it need to be returned?. many thanks.

CZwM67+vT+eikQVhBWyBUQ.jpg

Link to comment
Share on other sites

When you say alloy plate, if you mean the whitish coloured disc in the centre, that's the underside of the primary mirror.

A ten inch primary mirror blank is solid glass almost two inches thick, so the dried water droplet marks are totally isolated from the crucial front silvered surface.

I'd agree with the theory that they're where droplets have evaporated from condensation.  You could safely wipe them gently with a dampened piece of kitchen towel if you wanted to make certain, but there's no need to do even that really.

  • Like 1
Link to comment
Share on other sites

Those water stains are on the underside of your mirror, so in theory shouldn't affect your viewing. Other than that, my advice is to not touch your mirror. You're only going to be putting unnecessary wear and tear on the coatings and if you think about it, even after you've 'cleaned' the primary if you look at the mirror in the daylight it is still going to look dusty. Use a bulb blower to blow off any obvious debris, pollen etc after a night's session and leave it at that. In a good few years, if the primary starts to sprout its very own ecosystem, then it might be worth a tender wash, but only if it affects the contrast and quality of image :thumbright:

  • Like 1
Link to comment
Share on other sites

Good emphasis there from Rob, I should have qualified my remark about casually wiping the underside of the mirror.  That's fine, as the glass blank is very thick, but the top surface that is coated and shouldn't even be touched.

This photo of a ten inch mirror removed from the tube but still in its metal holder shows just  how thick the glass is compared to the diameter.

Needless to say, removing the Primary mirror "cell" like this should only be done with extreme caution and under extreme circumstances. It's too easy to drop it or touch it with hands or tools, which could immediately damage the mirror coating which lays on the front surface of the glass, unlike household mirrors which are coated on the back surface.

ten inch primary mirror.jpg

Edited by Astro-Geek
  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.