Hi Andreas..
If you do the collimation as per the ^ good instructions then all should be fine.
For ref;...
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http://www.skyandtelescope.com/howto/diy/3306996.html
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http://www.skyandtelescope.com/howto/diy/3306876.html
If you start by checking if the 2ndary is centred in the focuser tube,
then the off-set should be very close.
Regs, L..