Is this mirror too dirty?

[mwayne]

Is this mirror needing to be cleaned in your opinion?  Is there a benchmark or test for determining whether to clean? I'm hesitant to clean them too often for fear of scratching the coating.

Thanks! 

[estwing]

no its ok...leave well alone...clear skies!

[laudropb]

If the views obtained are ok then it is best left alone.

[alan potts]

It will be fine for a fair bit longer yet, never over clean things. I have had my Meade 12 inch about 8 years and I have cleaned the front once and couldn't tell the difference.

Alan

[cotterless45]

Don't clean it, until you can't see your reflection in it,

Nick.

[acey]

Yes it's dirty, just like mine. My windows and specs aren't spotless either but I can see fine through them. I can't remember when I last washed my mirrors, which is maybe a sign that I should start thinking about washing them again.

[swamp thing]

Looks about as dirty as mine. I re-coat my mirrors more often than I clean them . Basically I don't bother. 

[mwayne]

That's what I was thinking, but good to hear feedback from fellow SGLers. Thanks!

[estwing]

That's what we are here for, happy to help.

[joe1950]

I learned the lesson the hard way. I purchased a used ETX90 in excellent condition and with great optics - from the mid 1990s. It's the original RA version. The mirrors were bright and relatively clean, but the primary had a small smudge on it. So, not heading advice, I had to clean it.

Well, I cleaned it ok, right down to the bare glass.

You'll notice a dark area at about 10 O'Clock near the edge of the mirror. Looks a bit like Cuba. It's about 18mm x 6mm. How it happened, I don't know, but I'd much rather have the smudge.

It actually has no effect whatsoever on image quality, so I leave it as is. The rest of the mirror is still in excellent condition.

All the best.

joe

 

[Merlin]

That's quite a 'scope Joe if you can see Cuba in it ( wink ).

[joe1950]

And Merlin, I don't mind the aroma of a fine cigar wafting from the eyepiece holder 

[Merlin]

And watching salsa ( wink twice ).