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Yes it does have some effect but not enough to worry about. If you point the scope at a bright star and de-focus inwards, as the star image gets larger, more out of focus, you will see the shadow of the drawtube intruding into the out of focus image.
Considering that with most scopes the position of the drawtube with an eyepiece at focus will only be intruding into the light path by 10 or 20 mm, if at all it will be almost unnoticeable and have no effect on your views of the sky.
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