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Chipped primary skywatcher 250P 10" classic dob

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#1 Az_Rael

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Posted 18 June 2021 - 04:47 PM

Gutted right now. Got this scope a week ago and was removing the finder bracket for a different one while working on the scope vertically. Lesson learned about working on a reflector vertically. Finder bracket has a large metal reinforcement plate on the interior which was only attached with the two screws, so whole thing went clattering down onto the mirror.

Here is what I ended up with: http://imgur.com/gallery/gILS266

I am pretty new to the hobby and this is my first dobsonian. Based on some searches here, maybe I should remove the primary and black out the chips with a sharpie? Are these going to progress to cracks like a windshield would? Ugh.

Thoughts on how bad this is?

Gonna ping skywatcher as well and see how much a replacement will cost assuming I could get one before 2022.
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#2 moonrakercat

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Posted 18 June 2021 - 05:15 PM

HI Az - the damage won't make any difference to your views - if you had a new mirror and compared views with it to the one in the pics - you would not be able to tell the difference.   Everyone here will most likely echo this.

 

The only problem you may have in the future is if the aluminumizing starts to oxidize since the clear coating on the mirror is damaged - and that would be years & years down the road as long as you take care of that mirror.

 

I wouldn't sharpie out anything on it - I'm not sure if putting something on the chips - ie a small dab of clearcoat would help ?  You'll have to wait for others to chime in.

 

That mirror looks like it could use a cleaning.


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#3 Blueox4

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Posted 18 June 2021 - 05:18 PM

Well you learned a lesson and I would get the scope out and use it and see what you see.  Have seen pictures of a large reflector with bullet holes in it and the views were fine. I bet you will not see any visual issues and the scope will show good views. Do not black anything out. 


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#4 Az_Rael

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Posted 18 June 2021 - 05:59 PM

Thanks, hoping for clear enough skies tonight to take it out and check it.    

 

 

 

That mirror looks like it could use a cleaning.

It is brand new, only taken out twice last weekend, so I am a bit leery of cleaning it.   I have a camera bulb style air blower, might try that.  



#5 LuscombeFlyer

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Posted 18 June 2021 - 06:05 PM

Looks much worse than it really is. The biggest effect is likely to be its impact on resale value not its optical performance.

Lesson learned: never work on a vertical scope.
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#6 moonrakercat

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Posted 18 June 2021 - 07:10 PM

Your scope is still fine - you will enjoy it !

 

Learn to collimate it and learn how to clean the primary mirror - under water - very lightly with your clean hands - then wash the face off with distilled water & let it dry while vertical - your mirror has a hard quartz coat on it - albeit thin.

 

And don't drop anything more on it.!


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#7 moonrakercat

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Posted 18 June 2021 - 07:42 PM

Actually - if your brand new to this - don't clean the mirror - just get one of those compressed air cans & blow the dust off if there is that much - don't let anything touch the mirror dry - even a fine hair blow bulb brush is a no no.

 

Right now your afraid of your mirror - as well as somewhat disappointed - but trust me - you will learn to care for your mirror and over time you won't be afraid of it.



#8 Jon Isaacs

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Posted 18 June 2021 - 10:02 PM

Thoughts on how bad this is?

 

 

I am seeing a few small somethings in the region of the focuser.  

 

Consider their size and area compared to the secondary mirror.  Consider this size and area compared to the spider vanes. 

 

The effect they have is on the way you feel.  It's a bummer.  But figure you learned a lesson, those are minor battle scars and just move on.  In reality, everything is just fine and dandy.

 

Jon


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#9 Az_Rael

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Posted 19 June 2021 - 01:41 AM

Did get some clear skies tonight, and I wasn’t able to see any effects on the actual performance of the scope!   So all is well, just learned an important lesson.    Thanks everyone!


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#10 Shinzawai

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Posted 19 June 2021 - 06:05 AM

I can relate to the feeling! Hearing that crack/crash is gut wrenching.
I also learned the keep-it-horizontal (while adjusting the secondary) the hard way..

You're lucky in that it was only the primary, which is arguably a pretty tough nut. Put it back and you might not even notice is so simple that you don't even consider it in the moment.

The most important lesson I learned though is that there's still truly selfless and helpful people out there who go out of their way to help 'a stranger out'. (Thanks @astrokeith )

And without data to back it up, it sure seems that extends to most of the 'astro bunch' compared to insert-hobby-community!


Edited by Shinzawai, 19 June 2021 - 06:11 AM.

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#11 Az_Rael

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Posted 19 June 2021 - 02:21 PM

In case anyone is curious or finds this thread later, a replacement primary mirror from Skywatcher costs $600 plus shipping.   So, pretty much the cost of a new telescope.   


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#12 Tom Stock

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Posted 19 June 2021 - 02:47 PM

Imagine your secondary and spider as a huge chip and 4 long scratches in your mirror.

 

A bit more in the form of a chip isnt a big deal. You can black it out with a sharpie or drop of paint if you see any reflection from it when looking at bright objects.

 

The only real problem is the guilt of seeing it there.


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