Final answer:
An interferometer is a telescopic technique that combines multiple telescopes to improve angular resolution. By using this technique, astronomers can achieve better resolution than individual telescopes. The resolution of an interferometer depends on the separation of the telescopes used.
Step-by-step explanation:
The telescopic technique in which two or more telescopes are used in tandem to produce much better angular resolution than the telescopes could achieve individually is called an interferometer.
Interferometers work by combining electromagnetic radiation from multiple telescopes, which allows for a resolution equivalent to what would be obtained with a single telescope with a diameter equal to the baseline separating the individual telescopes. The resolution of an interferometer depends on the separation of the telescopes, rather than their individual apertures.
For example, two telescopes separated by 1 kilometer provide the same resolution as a single dish 1 kilometer across, although they are not able to collect as much radiation as a single large telescope.