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Strange marks on primary mirror


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Hi everyone
I have a 14 inch reflector that i got back in January and have used it quite a bit since then. When i went to go out tonight i noticed the primary mirror is covered in strange marks that i personally have never seen before on a telescope (I have owned several 8 inch reflectors for 13 years) I was thinking that maybe its something to do with condensation but i always take a hair dryer to the mirrors after each session to get rid of any dew. when i transport the scope or sometimes have to leave it in the van overnight i cover the scope in a duvet and put the heaters on full blast to get rid of any moisture on the outside, i also check the mirror the next day to see if any moisture has formed but as yet i haven't seen any form as a result of being left in the van over night. so i'm a bit confused as to what it is, I know shining light on a telescopes mirror can make it look a lot worse than it is but im wondering if these marks are going to effect its performance and if it needs to be cleaned off? Any help would be appreciated, thank you

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When it does come time to clean it though, bear in mind that what’s on the mirror is no ordinary dust, it’s very fine _sand_ and needs extreme care to clean it without leaving scratches 

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  • 2 weeks later...

Looks like the usual combo of dust, pollen etc

It doesn't need doing right now as it's not dirty enough to affect the view yet, but when you do come to do it here's one method - https://www.skyatnightmagazine.com/advice/how-to-clean-a-reflector/

Obviously you'll need a bigger bowl for the larger mirror, but you get the idea

Alternatively if you're not confident doing it yourself there are companies around that will do it too

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5 hours ago, doublevodka said:

Obviously you'll need a bigger bowl for the larger mirror, but you get the idea

I've read that the big Dob guys scrub down their bathtub and then line it with towels before partially filling it with detergent water to give their big primaries a good soaking.  The towels protect both the tub lining and the mirror from each other.

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As already said the mirror is not dirty enough to affect the view.

But if it bugs you then consider giving it a wash, it’s really no big deal if you’re careful and take your time.

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I used to use the shower to loosen particles and rinse our 20 inch mirror. I'd get the water to room temperature and then let the motion of the water do the work. I'd then use distilled water with the usual mix of isopropyl alcohol and detergent in it as final clean and then rinse thoroughly with de-mineralised water because there's a lot of calcium here. As others have said, if the dust is sandy it shouldn't be removed with a wiping action. Use dabs, changing the cotton wall after each one.

Olly

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  • 1 month later...

Thankyou for your help, I'll try and hold off cleaning for a while as it does make me nervous cleaning telescopes just in case I do scratch the hell out of it. It's a bit concerning that it's got that bad in just a few months but if it is the result of dust storms from the desert then I shouldn't be surprised. I think I'll  keep track of these dust storms in future and not go out if there is dust on the way.

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Here in Texas, I have to deal with smoke particles from wildfires to the west and northwest and agricultural fires to the south and southwest.  If the sky is hazy, there is an air quality alert, or I can smell smoke in the air, I simply don't take my gear outside at all to avoid gunking up the optics.

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