Andromeda Galaxy - 148 frames
Take 148 exposures. If we simply add them we get trails due to the Earth's rotation
The gaps are due to jogging the tripod while changing memory card - but it will not matter...
Some people worry about taking so many exposures. Will the shutter wear out? Canon rates the shutters in its EOS cameras at about 150,000 operations (mean time before failure). In 5 years I have taken about 35,000 shots, so there should be no danger yet. I expect reliability is similar for other brands.