Finding the right location for star gazing
Any number of interesting science fair projects can be based on astronomy. The main challenge to students based in urban areas is the fact that it is difficult to spot the stars at night due to the city lights in the night time. There was an interesting project undertaken worldwide some years ago when everyone on the planet switched off their lights at the same time to counteract this light pollution.
The correct term for this light pollution is skyglow. For any star based project to be successful you need to find the right place for observation to counteract this skyglow. In some areas the stars can be seen but not too clearly. This is not the best location to base a science experiment where you are trying to measure the intensity of light from different stars.
In such a case you could scope out other locations which would be more ideal. If your town has a telescope in the local observatory which is powerful enough, you could seek permission to make use of it for your project. Or you could modify your project by trying to find out which locations in the city you can view the maximum stars from.
You can pick five spots that are distributed all over the city and now map the most stars in each location. Stick with identifying about ten to fifteen constellations so that it does not get too complicated. Now base the science fair project on which is the ideal location for star gazing based on the place where the maximum constellations are visible easily.