Never use tap water alone, it dries and leave behind all the salts and other minerals on the primary. I have removed and cleaned mine, it's not that difficult. (This applies to my 200P). So first off, I stuck a bit of tape on the OTA and then on the mirror cell outer casing making sure both bits of tape were aligned so that when I came to put it back together, the cell and OTA go back in the exact same spot (important). I then undid the 3 or 4 screws that bolt the mirror cell to the OTA and gently lifted the OTA off the mirror cell (mine came of easy). I then left the primary soaking in tepid water with a little blob of washing up liquid for 5 minutes or so (the washing up liquid was none of that fragranced stuff, just pure washing up liquid) and then using surgical cotton wool (yes there are different types of cotton wool) moving gently from the inside out, very gently wipe the primary. I changed the cotton wool after every wipe, just in case I picked and dirt and grit up, didn't want to scratch the primary. Once done I propped it on its side (all the above had the mirror still in the cell) and poured IPA (Isopropyl Alcohol) over the mirror ,this will stop any streaks forming. I then left to dry, then aligned the 2 bits of tape on the cell and the OTA up and inserted the cell and screwed back together, quick collimation and job done. Took about 35 minutes. Good luck.