x = 218, y = 69, rule = B3/S23
124bo$123bo$123b3o6$118bobo$118b2o$119bo4$105bo$103bobo$104b2o$108bo$
106b2o$107b2o2$172bo$31bo138b2o$15bobo11b2o140b2o$16b2o12b2o110b2o35b
2o35b2o$16bo125bo21bo14bo36bo$140bobo22b2o10bobo34bobo$140b2o22b2o11b
2o35b2o$13bo14bo$14b2o10bobo33b3o34b3o34b3o34b3o26bo2bobo2b3o$13b2o12b
2o3bo170bobobo$30b2o34b2o35b2o35b2o35b2o22bo12b2o$13bo17b2o33bobo34bob
o34bobo34bobo21b2ob2o8bobo$13b2o36bo3bo12bo19bo3bo12bo19bo3bo12bo19bo
3bo12bo36bo$12bobo3bobo16b2o12bo3bo12b2o4b2o12bo3bo12b2o4b2o12bo3bo12b
2o4b2o12bo3bo12b2o4b2o29b2o$18b2o18bo12bo3bo19bo12bo3bo19bo12bo3bo19bo
12bo3bo19bo$2o17bo18bobo34bobo34bobo34bobo34bobo8b2ob2o$b2o36b2o35b2o
35b2o35b2o35b2o12bo$o3b2o12b2o175bobobo$4bobo10b2o23b3o34b3o34b3o34b3o
34b3o2bobo2bo$4bo14bo$113b2o35b2o11b2o22b2o$112bobo34bobo10b2o22bobo$
16bo95bo36bo14bo21bo$b2o12b2o94b2o35b2o35b2o$2b2o11bobo138b2o$bo155b2o
$156bo2$72b2o$73b2o$72bo$75b2o$75bobo$75bo4$61bo$61b2o$60bobo6$55b3o$
57bo$56bo!
Now that was an easy one, since it can be broken down into blinkers and eaters. The question here is how to synthesise other oscillators that aren't that simple, like 24P10 or 48P31. There are two main problems here: (1) how to derive a predecessor of the rotor comprised of still lifes and sparks and (2) how to provide these sparks. After that, assembling the actual synthesis should be easy.