This a handy ccd calculator
http://astronomy.tools/calculators/ccd_suitability
I recently got the same OTA and have used both the HG laser and Tak collimation scope. Both have given different results (the stock focuser doesn't help), close though, but have gone with the Tak scope adjustments after some research here on the forum ( yet to do a star test for confirmation ).
Have you got an unprocessed image or one without the PI star shrink process done ? Btw very nice image though