If you have a clear blue sky , just point the scope to the zenith , with your longest focal length eyepiece , 32-50mm , what ever you have ( the longer the better ) and look at the blue image , it should be evenly blue right across the field of view .
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look carefully at the edges for a darker blue you have vignetting and if the darkness is uneven side to side you have something in the light path
.. banana city
makes me laugh .
Brian.
Quote:
Originally Posted by E_ri_k
It was the best way I could describe them in that first image! I will have a look at the drawtube in the morning. Without the risk of sounding stupid, but is there a good way to check this during that day, other than looking for slop or sag in the focuser? Maybe take some flats and examine them?
Erik
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