said by ArthurS:The line wiring going into the fluorescent fixture is aluminum. The present ballast is wire-nutted directly to this wire. I bought a new ballast from Home Depot, but its wiring is copper, it's still in the wrapper, uninstalled. Perhaps I need to go to an electrical distributor to find a ballast suitable for aluminum wiring...
After a good laugh, (because there is no such thing as ballasts made for aluminum wire), the electrical supply counter-person, would just tell you to use wire nuts made for splicing aluminum to copper wire. Ideal Industries, for example, makes a very commonly used purple-colored Ideal #65, for this situation. It has a anti-oxidation compound inside, and a special alloy spring to connect the aluminum and copper wires. It is UL listed.
However,...
Evidence is recently coming out that even these wire nuts will not stand the test of time, and will fail eventually, because of the disimilar-metal effect, and overheating. They are still code-compliant as of now; although I could not find a listing on Ideal's website.
In your case, the load of the fixture is very small, and the aluminum house wiring is much, much larger than needed to handle the load. Therefore, it is not going to heat up; and you'll have no problem. I don't think I would use them anymore, for pig-tailing to receptacles. I suggest finding some, and using them.
There are other products, such as the Tyco 'COPALUM' connector - however, they require special tools and a Tyco trained & certified licensed electrician to install them: »
tooling.tycoelectronics. ··· home.stmThere are also other hard-to-find connectors, some of which are not UL listed.