Cost and weight data for optical and radio telescopes are analyzed to derive scaling laws appropriate to the design and costing of very large telescopes of the future. A scaling law exponent close to the 2. 0 power of aperture diameter is found for telescopes of comparable sophistication ranging from a 0. 4 m to 5. 0 m aperture, in contrast to the often cited 2. 7 exponent. Predicted characteristics for a 25-meter aperture steerable dish Next Generation Telescope (NGT) are 5 multiplied by 10**6 kg, 20 /kg and a total cost of 1. 3 multiplied by 10**8 .
