Part1- this is from Nick Smith @ Altair Astro.
Nick Smith @ Altair Astro if inside you can generally unscrew the front objective after removing the dew-shield and clean the back, but sometimes it looks as if the dust is on the back or inside when it's really on the front. You can blow the dust off first with a rocket blower. Never use compressed air as it will damage the lens by blasting dust grains against it. You can use an optical cleaning fluid or even
Part2- this is from ATS tips and Techniques.
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