A stargazer has an astronomical telescope by an objective whose focal length is 180cm and an eyepiece whose focal length is1.20cm. He wants to increase the angular magnification of a galaxy under view with replacing the telescope's eyepiece. Once the eye piece is replaced, the barrel of the telescope should be adjusted to bring the galaxy back into focus. If the barrel can only be shortened by0.50cm from its current length, what is the best angular magnification the stargazer will be able to achieve?