1. South African Astronomical Observatory, PO Box 9, Observatory 7935, Cape Town, South Africa
2. Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
3. George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A&M University, 4242 TAMU, College Station, TX 77843, USA