It is not an 'exact' scale but it is pretty close. Your scope would be 2700/150 or 200 so the slits would be 7-9mm slits 7-9mm apart. My scaled version would put it right about 5mm slits for your 180mm apature. Shot me your email in a PM and I'll email you the scaled version. Remember to download and install InkScape so you can view and print it out.