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Loose mirror ASA 12N


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#1 ChristerS

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Posted 15 March 2015 - 04:06 AM

Hi,

 

I have a ASA 12N I have trouble collimating. The problem seems to be that the mirror can move sideways  about 1 mm. 

When I moved the OTA from vertical +/- 45 degree a "cluts" sound appeared like something was loose. I removed the back cover and found out that I could move the mirror sideways a bit, like the mirror cell diameter is a bit to large for the mirror size, this movement make my collimation change. Has anyone notised this?

I asume this is not normal, is there something I can do or should I Contact ASA? 

I tryed to attached some foam (blue Arrows), se image, to keep the mirror from moving sideways, but that is not a permament solution. I have notised that the 12N OTA have the mirror not glued to the cell.

 

Best regards,

//Christer

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Cheers,
//Christer

www.astropix.se


#2 Daniel Schmid

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Posted 16 March 2015 - 12:23 AM

Hi

 

At least in case of the 10N the mirror is hold in place by 3 lateral screws (white PE screws) that are only accessible/visible when you remove the mirror cell. This might be different with the 12N but i think that there is a similar way of holding the mirror. 

 

I recently removed the mirror cell of my ASA 10N because of bad hysteresis and time flex measurement results and noticed that one of the 3 screws was loose (from transport?). To my comprehension theses screws should just touch the mirror glas but without any tension! The whole procedure to remove the cell, check the screws and put the mirror cell back in place took me about 10 minutes. Eventually you have to collimate again but if you only loosen the traction screws as described in the official ASA collimation manual on the last page you should end up quite close to where you started. In my case, collimation was even better after the procedure than before. Make sure that you put the mirror back into place at the same position as it was (mark position). Keep in mind that the mirror cell with the mirror is quite heavy!

 

I hope this helps!

Dani



#3 ChristerS

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Posted 16 March 2015 - 12:51 AM

Hi Daniel,

 

Thanks a lot for your input, I will give it a try if I dont hear something from ASA support.

 

//Christer


Cheers,
//Christer

www.astropix.se


#4 MarkS

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Posted 16 March 2015 - 01:38 AM

Christer,

 

Like Dani, I can only answer for the 10N - but I did have a case of loose mirror after I had collimated the primary and was too timid tightening the adjusting screws. During transport the screws loosened and the mirror bacame loose and rattled around in the housing! The plastic screws at the side were correctly set.

 

So it is important to check that the pull and push screws ARE tight - obvious, I know, but.....

 

Regards,

Mark



#5 ChristerS

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Posted 20 March 2015 - 11:16 AM

Hi!

 

I tighten the 6 plastic screws with a paper sheet inbetween the screws and the mirror cell and now the mirror is fixed. ;)

 

//Christer


Cheers,
//Christer

www.astropix.se





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