I have a skywatcher 150pds Newtonian. I have never collimated it before but obviously there's a first time for everything.... As I think is normal, there are three secondary mirror adjusters with allen key heads in the center of the spider, and a phillips-head screw right in the middle of yhe whole thing. Trouble is that neither the adjusters nor the central screw yield immediately to any turning force. I don't want to break anything so can I check - is the central screw supposed to be loosened before I touch the adjusters? Sorry for the potentially daft question, but it did almost seem like I was going to strip one of the bolt heads if I twisted any harder, and online search has not proved fruitful so far.
Many thanks