Figure 10. A MERLIN radio picture at 20-cm wavelength of the first gravitational lens to be discovered, 1956+561. To achieve the highest possible sensitivity, the LT was included in MERLIN. The radio intensity is represented in false colour and the two lensed images are the compact red objects above the center and towards the bottom of the picture. The 1956+561 lens system was discovered in 1979 in the course of a radio survey of the sky made with the LT.

Figure 11. Left: An infrared picture of the gravitational lens system 1933+504 made with the NICMOS camera system on the Hubble Space Telescope. Two of the lensed images are marked A and B. The central bright spot and the rest of the diffuse emission is associated with the intervening galaxy. Right: By studying the distortions in lensed images, a model of the mass distribution of the lensing galaxy can be determined. This picture shows the radio intensity contours of the 1933+504 lens system, made with the US Very Long Baseline Array, with images A and B marked. The intervening lensing galaxy is not a strong radio source and hence does not show in this picture. Various other extended images of the distant radio source can be seen. However, the signal-to-noise ratio in this picture is not high enough to show all the images which are known to be present. Including the upgraded LT into all VLBI arrays will improve their sensitivity and hence enable better mass models to be calculated for all known radio-loud lens systems.