So, I have an objective for my neophot 21 that was really dirty, and now it’s clean. Or at least, 99% of its area is clean, except for the actual front element, because it’s concave, and lens paper just harmlessly moves over it, without making any contact, so it’s still got a load of dirt on it.
Does anyone have some advice for cleaning a concave and small front element?
How can I clean a concave lens?
Re: How can I clean a concave lens?
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In principle, the radius of curvature of your cleaning tool needs to be equal to, or less than, the curvature of the lens surface.
… In practice, this is getting worryingly close to being “a pointy thing” … so the answer is with great care and considerable finesse.
MichaelG.
In principle, the radius of curvature of your cleaning tool needs to be equal to, or less than, the curvature of the lens surface.
… In practice, this is getting worryingly close to being “a pointy thing” … so the answer is with great care and considerable finesse.
MichaelG.
Too many 'projects'
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apochronaut
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Re: How can I clean a concave lens?
The small concave front element is a physical artifact associated with increased planarity of the lens and in my experience is part of the design package occuring with an embedded front lens. This arrived on the scene in the 1960's patented by AO and developed by Arthur Shoemaker, one of their senior optical designers. Everyone used them subsequently.
In the AO manuals for microscopes that used such lenses , they have specific instructions for cleaning the front concave surface. You even get a picture of a staring eyed man performing the procedure.
They recommend removing the objective, turning it upside down, then removing an eyepiece and turning it upside down , using it as a 10X magnifier to view the front lens. If required, clean it with lens cleaner and a quality cotton swab. The picture shows one of those single end fancy types with a long wooden stick but I've used q-tips and they work fine.
In the AO manuals for microscopes that used such lenses , they have specific instructions for cleaning the front concave surface. You even get a picture of a staring eyed man performing the procedure.
They recommend removing the objective, turning it upside down, then removing an eyepiece and turning it upside down , using it as a 10X magnifier to view the front lens. If required, clean it with lens cleaner and a quality cotton swab. The picture shows one of those single end fancy types with a long wooden stick but I've used q-tips and they work fine.
Re: How can I clean a concave lens?
Take some soft wood stick wrap medical cotton wool around it and soak it with some optical cleaner. Instead of the cleaner you may use a mixture of ethanol and ether for good results.
Re: How can I clean a concave lens?
I used the blunt end of a skewer with lens paper wrapped around, and 80% ethyl alcohol, worked pretty well.
Re: How can I clean a concave lens?
I second what apo said. I've cleaned lots of objectives that way. Perfectly safe as long as you do it gently.