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Dark spot on lens?

mfo

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Well, I noticed that today there's a dark spot on my 405-G-1 lens when unfocused. I tried cleaning it with a q-tip, tried putting a dab of alcohol on the q-tip and cleaning the lens, tried using compressed air, nothing works. Anyone here have any idea what gives?

It's not the diode, the diode itself is 100% clean. I removed the lens and pointed it at my ceiling and it was flawless.
 





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I'm assuming it's either 445nm laser or 405nm laser being focused through it, both of which are available only in "Holy-sh*t-lookathat" level of powers today.

If a spec of dust or something settled on it when you had it turned on, it most likely baked on it pretty hard. I'd not advise rubbing very hard on the lens with q-tips, but try leaving a drop of cleaning alcohol on it for a while, until it evaporates on it's own, then try to clean it again (it should soften if not take apart the little baked particle on it).

I don't think of any other reason which can cause this.
 
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mfo

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I'm assuming it's either 445nm laser or 405nm laser being focused through it, both of which are available only in "Holy-sh*t-lookathat" level of powers today.

If a spec of dust or something settled on it when you had it turned on, it most likely baked on it pretty hard. I'd not advise rubbing very hard on the lens with q-tips, but try leaving a drop of cleaning alcohol on it for a while, until it evaporates on it's own, then try to clean it again (it should soften if not take apart the little baked particle on it).

I don't think of any other reason which can cause this.

Yeah, it's a 12x. How would I know I've damaged the lens? I know I didn't I was very gentle, just curious.
 
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mfo I don't think a 12x set to the max will damage the AR coating on the lens. You can try soaking the lens in menthol alcohol "or the purest alcohol you can find" for half an hour or so. It's possible the the lens has a manufacturing defect from when the lens was ground. Sorry I can't be more helpful.
 
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I'd be careful using Methanol on the AR coating. Not only would you get the dark spot off but you might kill the AR coating as well.
I have no idea what the AR coating is put on and I'll assume it could be dissolved in strong Alcohols.

Anyone clear this one up? Feel free to interject if I am being paranoid here.
 
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Dude if you necropost one more time I'm going to rep you.

BTW nothing over the counter will dissolve that AR coating.
 
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Re: Dark spot on lens? :?:

Dude if you necropost one more time I'm going to rep you.

BTW nothing over the counter will dissolve that AR coating.

I have no idea what you are on about, "necropost"?
I say this about the coating because I managed to kill the coating from an olike lens by using
Methanol. I agree it shouldn't have come off at all. Generally one requires an acid to remove the coating, however.... cheap lenses/ cheap coating = dead lens.

This is an aside...
 




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