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Old 03-03-2019, 07:19 PM
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BlackNebula (Mark)
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HELP!! I broke my primary mirror

Hi, just did the most stupid thing!! I overtightened the focuser on my Nexstar 8se. I heard the crack and now have a large 1x2 cm chip on the edge of the primary mirror (see attached photos). This has just turned into the worst day ever!! I think the mirror is a 8Ē F10.

Not sure what to do, is the OTA stuffed?
Can I replace the primary, or fix it or if I leave it with the chip will this affect the viewing?

Please help, any advice will be most appreciated.
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Old 03-03-2019, 07:36 PM
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mental4astro (Alexander)
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Ok, not the best thing, but not the worst.

The good news is the chip is circular, so ypu won't see any additional diffraction spikes ilike if the chip had a straight edge. Another good thing is though it looks HUGE, the % lo st isn't all that significant. Your bird can still fly!

If you like, you can paint the chip matt black to stop any reflections that may come off the substrate glass, being carefull to keep the edge round. Or cut a similar sized scallop out of black self adhesive felt to put over the chip to do the same jib as paint - could be easier and safer than paint. I've got plenty of the stuff and wpuld be happy to post you out a piece rather than you buying a whole lot for just a small piece.

Alex.
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Old 03-03-2019, 08:03 PM
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You must have a screw that is too long and interfering with the movement of the mirror.
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Old 03-03-2019, 08:08 PM
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Thanks Alex, thatís awesome news. One question, Wonít the area of the mirror where the screw moves the mirror to focus be weakened as it would be directly behind the chip?
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Old 03-03-2019, 08:09 PM
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Also, would using a sharpie to color the chip black not maybe work?
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Old 03-03-2019, 08:21 PM
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+1 What Alex said. Black mate the center of the chip and any sharp edges. You won't see much difference as the damaged area is a small part of the total mirror surface. What Tony mentioned is more important to figure out what happened. You're lucky your mirror didn't split. Then you'd be up the sh!t creek for a brand new ota.
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Old 03-03-2019, 08:24 PM
casstony
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You can't chip the mirror by turning the focuser unless the mirror hits something. Eg. A mounting screw on the side of the tube that is too long
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Old 03-03-2019, 08:38 PM
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Over-tightening the focuser would not normally achieve that result. I would investigate the true cause - if the product came with an overly long screw that struck the mirror when you racked it all the way in for the first time then Meade are quite probably still liable to fix that issue under Australian Consumer Law, which does not expire after 12 months as some believe.

Otherwise, a splash of matt black will do the trick, but even then I would only do it if you can see light scattering on bright objects. Just be careful transporting your OTA with that shard of glass rolling about inside
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Old 03-03-2019, 08:54 PM
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Can confirm shouldn't affect images too much.

Source: I have some chips!
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Old 03-03-2019, 10:13 PM
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Thanks for all the responses, ya itís just weird, Iíve had the scope for about 8 years now with no issues at all. So, donít understand how I managed to do this!

But it seems like I can fix this, just hoping thereís no bigger issues waiting behind the mirror

Iíll take it apart and mat the chip and see how it goes. Iíll post an update once done. And I was going to try some new eyepieces tonight with my also new NexYZ smart phone adapter, bloody hell!
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Old 03-03-2019, 10:19 PM
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Take heart from this.
The telescope went on to do many years of astronomical work and discoveries.
https://astroanecdotes.com/2015/03/2...ting-incident/
Cheers

Last edited by astroron; 03-03-2019 at 11:26 PM.
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Old 03-03-2019, 10:57 PM
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Wow! Okay, thatís pretty hectic. Mines not so bad I guess, but it still hurts, big time
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Old 03-03-2019, 11:27 PM
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Quote:
Originally Posted by AstroJunk View Post
Over-tightening the focuser would not normally achieve that result. I would investigate the true cause - if the product came with an overly long screw that struck the mirror when you racked it all the way in for the first time then Meade are quite probably still liable to fix that issue under Australian Consumer Law, which does not expire after 12 months as some believe.

Otherwise, a splash of matt black will do the trick, but even then I would only do it if you can see light scattering on bright objects. Just be careful transporting your OTA with that shard of glass rolling about inside
I agree, if you think about it logically there has to be safety built in for when people DO go at things heavy handed, and also when focus motors are fitted there are (as I found by contacting Celestron and asking) HARD stops at each end of travel so this will not happen, either you turned it with more force than should be expected or as said here there is another reason
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Old 03-03-2019, 11:34 PM
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Quote:
Originally Posted by BlackNebula View Post
Wow! Okay, thatís pretty hectic. Mines not so bad I guess, but it still hurts, big time
Yes it would hurt,I feel your angst.
I have a Celestron Ultima 8 20cm SCT I bought in the states 29 years ago
it is still going strong.
Here's hoping you get many more years of use from your's.
Cheers
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Old 03-03-2019, 11:47 PM
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Quote:
Originally Posted by multiweb View Post
+1 What Alex said. Black mate the center of the chip and any sharp edges. You won't see much difference as the damaged area is a small part of the total mirror surface. What Tony mentioned is more important to figure out what happened. You're lucky your mirror didn't split. Then you'd be up the sh!t creek for a brand new ota.
Which could still happen if the problem is not corrected, was it bought NEW or used if NEW and the fault can be shown as manufacturing the Celestron would be liable
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Old 03-03-2019, 11:56 PM
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I bought it new, how would I determine if this is/was a manufacturing fault?
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Old 03-03-2019, 11:59 PM
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Thanks Ron, I sure hope so. Itís a great scope, real easy to set-up
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Old 04-03-2019, 01:33 AM
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Quote:
Originally Posted by blacknebula View Post
i bought it new, how would i determine if this is/was a manufacturing fault?
i have sent you a pm

For others reading it, the PM is a legal letter to get the manufacturers to look at it whatever the age

Here in the UK there is NO such thing as "guaranteed for 12 months" that is understood, the Consumer rights act (you may have similar) means that goods should remain fault free for a reasonable time depending on VALUE as well, hence a $5 pair of shoes could remain fault free for 3 months, a $3000 watch could any reasonable time, say 5 years.

I had a monitor that was faulty after 18 months, the manufacturer said "tough 1 year" the small claims court disagreed, it cost me £50 to go to court, one new monitor and £50 back and my postage costs

Look into

https://www.accc.gov.au/consumers/co...ees/warranties


SEE

The consumer guarantees which apply regardless of any warranties suppliers sell or give to you, apply for a reasonable time depending on the nature of the goods or services. This means consumer guarantees may continue to apply after the time period for the warranty has expired.


Too few people bother to check their rights and when told tough fail to go back again and again, they give up, one of the best things about the fact that I am Autistic, ADHD and Aspergers is that I am like a dog with a bone and in 40 years I have never lost
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Old 04-03-2019, 09:29 AM
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The primary of a typical 8" SCT is f2 with a f5 secondary giving a f10 system. The Schmidt correcting plate is also a vital component and usually matched or at least oriented (rotated) to give the best optical test result.

You are best to seek professional advice from an authorised dealer.
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Old 04-03-2019, 09:39 AM
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I recall with a friend's C11 a similar problem with the primary mirror. We found the problem was the screws that coupled the finder scope were interfering with the primary. Not because they were too long, but as we were not using that finder the screws had been left in the OTA so they were not lost nor allow dust to get in. So, as the finder scope bracket was not in place, these scews were then protruding further into the tube and so interfering with the primary. We noticed some interference when focusing, but we didn't force anything.

Mark, by any chance had you left some screw/screws in place that would otherwise be holding a finder or dovetail plate? If after so many years of using the scope it is extremely unlikely that you would have over-wound the focusing mechanism to carelessly cause this to happen. But if you had left a screw or two in place, then this would have been a very likely accidental cause.
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