There's not, and we've been redefining where we really think the border is, even within the past year or so. There's a lot more globular clusters - relatively s

There's not, and we've been redefining where we really think the border is, even within the past year or so. There's a lot more globular clusters - relatively small clusters of stars, etc. - that are gravitationally bound to galaxies than we previously knew. These can extend quite a distance out. Their relatively low density and distance from the main portion of the galaxy means that even if you brightened them, they'd largely just look like other stars in the sky and would be hard to distinguish from being part of the general background of stars our galaxy provides, so there wouldn't necessarily be much point in doing so.