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MN190 Secondary Twisted

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I need to align my secondary again after it twisted when I loosened the fourth locking screw on the secondary attachement. It basically rotated the secondary cell inside the corrector cell.

I tried the laser and a home made Cheshire but just cannot get it to produce good stars to the edge. CCDInspector is used to analyse the final result.

Is there a way that I can take flats against a lit wall (setting the DSLR to AV as you do with sky flats) and then somehow figure out from that via CCDI if I have the required rotation set correctly? Would this be a good way of getting the rotation set correctly?

I do not think that there are any issues with the lateral positioning of the secondary. It appears well centred under the focuser. I just cannot seem to get the rotation set correctly.

I would appreciate any advice on what has worked for you or what I can tick off the list as not even having to try this or that.

Are there any commercial products available that can be recommended as the sole tool you require to get this scope tuned collimation wise to its full potential? (secondary setup as well as primary)

Any advice or views would be greatly appreciated.


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Did you have good stars prior to this? I take it there may have been an issue otherwise why would you be adjusting the secondary?

The usual way is to rotate the secondary by hand. It is awkward but can be done. You will probably need to loosen the clamp ring (using a wrench and a cardboard shield to protect the corrector)

What shape are your stars ? Like this perhaps (ignore the look of the sub, its the star shapes that are the interesting bits)?

I can fine tune the collimation my scope on the night using CCDInspector so the stars are nicely round. Next time I am out though they are back to having a flat edge. My setup is fixed. I suspect heat might be a problem.



An excellent but strange scope




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