EwanV Posted May 21, 2021 Share Posted May 21, 2021 We all know what it's like - a friend passes on a great piece of advice and you ignore it, only to regret it almost immediately. This thread is for those of us who "thought they new better" and want to save others from the same mistake as well as the smug gits who's mate saved them a fortune. Let's start with this one from a very good friend of mine about cleaning your mirrors and lenses: "If you ever get the urge to clean your primary mirror or objective lens, the first step is to make a cup of tea and sit down until the feeling has passed" So you've got a dusty primary mirror. It's a 150mm diameter, so it's surface area is (75mm x 75mm x 3.14) 17,662.5mm^2. That's a lot of square millimeters!! A dust particle will be 1 to 100 microns in diameter (0.01 to 0.1mm) and if you do the maths you'll see that you would need somewere between 2,250,000 and 225,000,000 dust particles to completely cover your mirror. The dust stands out when you look at the mirror, but you don't notice all the gaps between the particles. Let's say that you've been unlucky enough to get 100,000 particles of an average 50 microns across. That's (0.025mm x 0.025mm x 3.14 x 100,000) 196.25mm^2 or just over 1% of your mirror. 99% of it is still clear. The clips holding the mirror in place are actually covering more surface area than the dust!!!! LEAVE IT ALONE!!!! 1 Quote Link to comment Share on other sites More sharing options...
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