Gravitational lensing is one option, but another is the Terrascope concept whereby the Earth's atmosphere would be used as a refractive lens. In theory, any at

Gravitational lensing is one option, but another is the Terrascope concept whereby the Earth's atmosphere would be used as a refractive lens. In theory, any atmosphere would do. It may even be possible to use Jupiter's outer atmosphere. As refraction is stronger than gravitational lensing, such schemes would not require multi-decade trips out focal points at edges of the solar system. https://arxiv.org/abs/1908.00490 https://arxiv.org/abs/1908.00490