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Mirror question

Mirror Making
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#1 RodgerDodger008

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Posted 01 January 2022 - 10:52 AM

About 3 months ago I got my first scope, the 8 inch in my signature.

It was brand new and as the norm these days with anu product nothing is ever perfect, also some imperfections does not really impact the end use on so much as one can notice.

On the outside of the mirror (the with the colomation screws) it seems to be frosted, there is about a fist sized area in the middle of that with the frosting not there in a somewhat untidy smudge circle. I can see what i think is the underside of the mirror coating through the glass there. No biggie.

So tonight i shined a flashlight from the back and looking down the tube i see maybe 5 or 6 pinpricks of light.

I have read enough and learnt enough to know this will not even have a impact of 1% on my views.

My question is two fold, is my assumption correct and how common is these sorts of defects on new dobsonian scopes.

Any other thoughts welcome.
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#2 TheUser

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Posted 01 January 2022 - 11:32 AM

can you provide a photos?

 

there are many criteria of the mirror quality. pinholes is not the only


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#3 sevenofnine

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Posted 01 January 2022 - 02:40 PM

Yes, you are correct. The backside of the mirror is of no consequence. The pinholes don't matter either. Neither does the eventual dust or specs. I read somewhere that the best way to examine a mirror is when you look down the tube to shine the flashlight at your face. If the image looks sharp then all is well. Shining the light at the mirror surface will drive you crazy and for me, it's a short drive gaah.gif   


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#4 RodgerDodger008

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Posted 01 January 2022 - 05:41 PM

can you provide a photos?

 

there are many criteria of the mirror quality. pinholes is not the only

I doubt it will look anything but pristine in photos.



#5 RodgerDodger008

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Posted 01 January 2022 - 05:44 PM

Yes, you are correct. The backside of the mirror is of no consequence. The pinholes don't matter either. Neither does the eventual dust or specs. I read somewhere that the best way to examine a mirror is when you look down the tube to shine the flashlight at your face. If the image looks sharp then all is well. Shining the light at the mirror surface will drive you crazy and for me, it's a short drive gaah.gif   

Lol yes for sure. 

 

I saw someone on here comment years ago that pinholes can sometimes exist even after newly coated because the coating is so thin to preserve mirror shape.


Edited by RodgerDodger008, 01 January 2022 - 05:48 PM.

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#6 ShaulaB

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Posted 01 January 2022 - 07:23 PM

Relax, what you see is of no consequence for viewing. Learn to collimate the scope well. That skill will come after lots of practice. Enjoy your scope. Dress warm in the winter.

The nice thing about an 8 of nch Don is it can fit into just about any vehicle for driving to darker skies.
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#7 RodgerDodger008

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Posted 01 January 2022 - 07:55 PM

Relax, what you see is of no consequence for viewing. Learn to collimate the scope well. That skill will come after lots of practice. Enjoy your scope. Dress warm in the winter.

The nice thing about an 8 of nch Don is it can fit into just about any vehicle for driving to darker skies.

Thanks for confirming.




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