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If you read the literature it states that shining a torch down the scope is not a good test of the optics. It states that you will see what looks like defects in the mirror figure and surface and that those defects do not really exist. Those smudges are present on my scope and I have nice optics and have gained some great Jupiter, Saturn and Mars images. So shining a torch down the tube of an SCT will only play tricks with your mind.
I have not noticed this effect on newtonian mirrors. Perhaps the corrector plate is the caussative factor here.
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