  This paper discusses the hardware and software components of the Grid
Computing system used to implement the Locus Algorithm to identify optimum
pointings for differential photometry of 61,662,376 stars and 23,799 quasars.
The scale of the data, together with initial operational assessments demanded a
High Performance Computing (HPC) system to complete the data analysis. Grid
computing was chosen as the HPC solution as the optimum choice available within
this project. The physical and logical structure of the National Grid computing
Infrastructure informed the approach that was taken. That approach was one of
layered separation of the different project components to enable maximum
flexibility and extensibility.
