The notion of using an astronomical object as a telescope has inspired research, some of it very speculative. Gravitational lensing and gravitational microlensing have already been used for this: working out characteristics of the more distant body from the lensed electromagnetic radiation. Current sheets in the interstellar medium, which refract, have been used as lenses. Undoubtedly these methods will continue to develop.
The notion of using solar system bodies has been considered. I presume gravitational lensing offers too little bending to be of much use in this case. Using refraction by the atmosphere that surrounds a body has also been considered, with Earth is a prime candidate. In a transit or eclipse of a body passing behind another that has an atmosphere, a changing pattern in EMR that has passed through that atmosphere can be analyzed. Such a method might be applied to extra-solar planet investigations or other interstellar applications.
There may be clouds other than current sheets that produce the kind of refraction needed to be used as a lens, also offering possibilities.