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Is my secondary mirror normal

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#1 teucer

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Posted 17 October 2020 - 10:09 PM

I was trying to collimate this scope, new in the mail. It is a 190mm Maksutov Newtonian. I see this circle type artifact on the mirror. Not sure what it is and it seems too uneven to have been put there intentionally. Looking for other opinions.

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#2 cuzimthedad

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Posted 17 October 2020 - 10:18 PM

Hi teucer and welcome to Cloudy Nights. I'll let those who own or have experience with a Mak-Newt answer your question, but I just wanted to reach out and welcome ya to the forums.



#3 teucer

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Posted 17 October 2020 - 10:20 PM

Thank you for the warm welcome.


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#4 Jim Waters

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Posted 17 October 2020 - 11:15 PM

If you didn't put that circle there I would send it back and get a replacement.


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#5 teucer

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Posted 17 October 2020 - 11:32 PM

Nope; I didn’t put the circle there...


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#6 chubster4

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Posted 17 October 2020 - 11:52 PM

Is this a diagonal mirror? (Looks like there's an out-of-focus secondary in the background.) If it's in the center of the mirror, it was probably put there to aid in collimation. If it's small enough, it might fall within the shadow cone of the secondary mirror and not be noticeable, but I'd rather not have it there. 



#7 teucer

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Posted 18 October 2020 - 08:41 AM

Yep. It is the diagonal miror.


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#8 Vic Menard

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Posted 18 October 2020 - 10:39 AM

It appears to be an alignment reference for the secondary mirror placement. The 190MN requires precise secondary mirror alignment to ensure that the meniscus is correctly aligned. What collimating tool(s) are you using?


Edited by Vic Menard, 18 October 2020 - 10:40 AM.


#9 teucer

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Posted 18 October 2020 - 11:05 AM

I am attempting to use a cheshire collimator (not shown in photos).


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#10 Vic Menard

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Posted 18 October 2020 - 12:24 PM

Can you get an image of your alignment through the Cheshire?



#11 teucer

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Posted 18 October 2020 - 12:36 PM

Ok. I’ll see if I can do that today.


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#12 teucer

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Posted 18 October 2020 - 03:11 PM

Focuser all the way out...

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#13 teucer

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Posted 18 October 2020 - 03:12 PM

Focuser all the way in.

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#14 Vic Menard

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Posted 18 October 2020 - 04:29 PM

Focuser all the way out...

OK, that's not far enough out. You'll need to pull the sight tube out away from the focuser/adapter to reveal the actual edge of the secondary mirror (which isn't visible in your image). If the sight tube is too long, (or the travel too short) to reveal the actual edge of the secondary mirror, you may need to invest in a simple collimation cap like the Rigel Aline (or a good 2-inch sight tube).


Edited by Vic Menard, 18 October 2020 - 04:37 PM.



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