the program looks great! just another idea, it would be cool to allow the program to store multiple locations, and adjust the local time and sky plot accordingly, so the user can quickly switch to user preset locations (eg, new york, london, capetown etc). also, city light pollution effects could be used to block out dim stars, an effect could be similar to star filters, where level of light pollution can be adjusted. (similar to atmosphere effect, i guess, but adjustable) hope this helps to give new directions for later versions

cc