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HELP - dob cover


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Just now I was getting my scope ready for observing and I noticed some dust on the primary mirror (it's an orion xt8).

I was amazed since I have it for only a couple of days and only used it once. After inspection I noticed the cover scraps the tube paint creating small (not that small actually) particles that drop into the primary.

1st) Anyone else noticed this on similar scopes?

2nd) How do I solve it?

I thought maybe making a cover myself, one that fits the tube from the outside instead of the inside.

I also need advise on how to best clean up the primary without damaging it!

PS-> I can't really understand how can a product so well rated have such a stupid design flaw!

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I solved part of the problem. I broke the plastic "clips" on the cover (lid) of the tube. Without them it fits the tube but doesn't scratch the paint, so no more paint scraps falling into the primary.

Only problem now it the lid doesn't stay fixed to the tube, but with a piece of cloth in between the lid and the tube, it stays fixed and reduces the risc of scratching even more.

I still need advice on how to remove the dust that's still on the primary without damaging it.

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tbh a little bit of dust won't make any noticeable difference. if you feel that you have to clean it there are a lot of folk (braver than I!) who have removed and cleaned their primaries..... so you should find quite a few threads if you search appropriately

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tbh a little bit of dust won't make any noticeable difference. if you feel that you have to clean it there are a lot of folk (braver than I!) who have removed and cleaned their primaries..... so you should find quite a few threads if you search appropriately

I'll probably let it be there for now, since I didn't notice a decrease in quality when I used the scope last night. Still it's bad to have something new and already imperfect.

I thought maybe shoving my arm down the tube with a compressed air can and blowing the dust aside without touching the primary at all. Don't know if its a good idea...

I did some search without much luck, but I'll try again.

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i don't think compressed air cans are the best because some of the propellant might get on the mirror. also if you just blow it off like that, won't the dust just settle back on the mirror? I think you can get air blowers/ lens pens that don't rely on propellants that are more suitable if you decide to go down that route....

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There is a small gap, just a few mm, between the mirror an the tube. I though maybe I could blow the dust into the gap and it would fall behind the primary and into the back of the tube.

But as you said it's risky. As much as I'm disappointed by having a dirty scope thats less then 1 week old, I'll just get a hold of myself and learn to live with it :D.

I'll leave the whole cleaning idea aside for now. At least I have the cause of the dirt taken care of.

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I think you just need to get used to the idea that your mirror is open to the elements and live with it - you'll never see a clean mirror unless it's never been outside.

Arthur

I can live with that. Problem is it wasn't the "open elements" that made it dirty. It was the lid provided with the scope that scratch the paint on the inside and made it dirty.

That kind of design flaws make me mad. I work as a engineer designing both hardware as software solutions to solve specific needs of costumers. If I sell a product to a costumer with this kind of easy-to-solve flaws my phone will be ringing pretty soon and it won't be a pleasant conversation. :D

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I know what you mean about the the tiny paint flakes, I think I had that with my old Orion 8-inch too, though among all the dust that gathered they weren't noticeable and I never took any further steps beyond periodic mirror cleaning (once every year or two, or four...). Dust on a brand new mirror is unsightly, dust on a mirror that's a few weeks old is a good sign - it means the scope's getting used.

Never clean a brand new mirror as the coating hasn't yet hardened through natural oxidation. Wait a few months at least. Otherwise you're far more likely to end up scratching it.

I found with my Orion that the fit of the tube cover depended on temperature, it contracts in the cold and gets looser.

The Skywatcher 12" I now use has clips on the cover, my Orion Skyquest didn't. When I drove the Orion home in the car the cover would simply drop off because it had got loose with cold. This doesn't happen with the Skywatcher.

If you aren't happy with your dob lid then you could try a piece of cloth held on with string.

Whatever you use, it will deposit a certain amount of stuff on the mirror, but you'll never notice the effect at the eyepiece.

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Thanks all for the help and advice.

I'll leave the primary alone and enjoy my new hobby as much as possible. I'll take your advice and will only clean it when the amount of dust starts to be noticed in observations.

If I came across impolite, my apologies.

I just get a bit cranky when I buy things that don't seam well constructed and lack the sense of care for details. I usually prefer to spend the extra cash on quality then having this kind of small problems. In my research Orion came up as a good brand so that's why I got a little disappointed by having problems with the scope right from the start.

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It takes an awful lot of dust to impair the view from your scope. A compressed air can should be safe if you keep it 6 - 8" from the surface. Do not under any circumstance use a vacuum cleaner as a blower, that'll just make things worse.

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