Not sure if I have ever heard of something like that. But I generally figure
out what the limiting mag my scope will work at, then look for targets in that
range. Most astro softs free or otherwise allows you to set this (limiting
magnitude) within the program, you then print charts up...etc...etc... within
the range of your scope.

If your new to the hobby, Messier objects are probably a good place to start
as most are generally fairly bright. And you should be able to nab them with
your 4.5"

regards,CS