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New Celestron Evo 9.25 - fantastic, but slight concern

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Hi all,

Just to introduce myself, I'm Tim, from Harlow Essex, and I'm and brand new to astronomy, having bought my first telescope just this week. Myself and the family are already enjoying it immensely with the great views of Jupiter and its moons right from day1.... stunning, and has totally exceeded our expectations! 

This forum looks to be a great resource, and I expect to come here often to get the views and advice of all you seasoned astronomers.

So the main reason for my first post is that I have a slight concern with my new purchase. It was bought with a discount, and I'm told it was from a customer who returned it after a couple of days with a faulty main board in the mount - now replaced, or course. To be honest, it all looks absolutely brand new, and even still had the protective film on the various parts. 

I really am extremely happy with it other than that I've noticed three tiny specks on the objective lens. I've tried to blow them off using a puffer, but it's now clear to me that either they are dust particles on the inside of the lens, or possibly even slight flaws in the glass (does this happen?).The specks are just below the centre piece of the lens. (sorry, I don't know the name of that part). I've attached a couple of photos, which I hope shows what I mean.

Being a novice, I've really no idea if this is something I should be concerned about, or whether it warrants raising with the retailer, so I thought I should first seek the unbiased opinions of those who know far more than I do. I'm hoping it's nothing to worry about.

Thanks in advance for any advice,




Edited by werewhelk
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Welcome to SGL Tim. The glass disc is called  the "corrector plate". Those specks will not interfere with viewing. Over time, you will get many more and the scope is very tolerant of some dust & debris. Just ignore them and enjoy your new scope. Very nice unit for your first scope by the way.



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Thanks for all the replies, and for putting my mind at ease, I knew I'd some to the right place!

And it's the corrector plate, i see. Lots to learn!

Really appreciated guys.


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Hello and a warm welcome to the SGL. I am glad that your concerns are now laid to rest. Please feel free to ask questions as they arise. They are a great bunch on here and will always be ready to help

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I bought a brand new nexstar 127 SLT in February and a brand new CPC800 in April and both have 2-3 specks of dust on the inside corrector plate.

i was worried at first but I think it's normal and it doesn't spoil any observing.

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You get this kind of thing with just about all optical equipment, astronomical, photographic, and so on. I used to worry about dust on my camera lenses too, till I learned that trying to clean optical surfaces can sometimes cause more problems than leaving a few harmless dust specks where they are. Often, cleaning an optical surface with a cloth, even a soft dedicated one, can just serve to turn a speck into a scratch, and quite a few lenses have been spoiled by over-enthusiastic cleaning. I can no longer find it on the inter-thingy, but I used to direct people to a web site which showed a camera lens (it was a Zeiss Planar, he must have wept when he did it) which the owner had accidentally scored deeply right across the whole front with one of those Dremel tools with a grinding tip on it. It had flown out of his hand, and cut a trench right across the diameter. The damage was bladder-weakening. However, he also showed some photographs he'd taken with it after the damage, and you simply wouldn't know there'd been anything wrong with the lens at all. The moral of the story, of course, is that if you use a grinding tool near an expensive lens, you should be locked up for your own safety, but tangentially, a little dust is never something to worry about.

Unless it was in your suitcase and a police sniffer dog is nosing it. Then your troubles are astronomical, in a different way.

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IF the corrector ever needs cleaning - please don't assume it's just a normal piece of glass and start cleaning it like a window in the house. Ask us how it's done safely (for the optical-coatings) and properly. Your corrector-plate will reward you greatly! :D

Clear skies & corrector-plates,


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