Question on using the sun as a telescope lens

[kempdav]

I read an article on using the sun's gravity as a giant telescope lens. See https://www.space.com/earth-like-exoplanet-imaging-with-sun . Great idea but it said the focal point is too far away to use this idea right now.

What I don't understand is why we have to jump straight to using the sun. Why not use a large planet like Jupiter instead that would have a focal point much closer? The sun is roughly 1,000 times bigger than Jupiter so using Jupiter instead of the sun would provide a focal point roughly 1,000 times closer than 550 AU. Of course it wouldn't be as good as using the sun but would be much more powerful than any telescope that we have built so far.

Also, if we are thinking of using the sun's gravity, why stop there? Why not think even bigger and look at using the gravity of a black hole for a telescope lens? The focal point would be much much farther away. However, maybe there is a distant black hole whose focal point is close to our solar system - potentially close enough that we could reach it with current technology.

 

[Helio]

The lesser mass of Jupiter will bend light less, thus the focal length will be much farther. Perhaps ~5000AU.

 

[Kerluke]

Telescopes are meant for viewing distant objects, producing an image that is larger than the image that can be seen with the unaided eye. Telescopes gather far more light than the eye, allowing dim objects to be observed with greater magnification and better resolution. Although Galileo is often credited with inventing the telescope, he actually did not. What he did was more important. He constructed several early telescopes, was the first to study the heavens with them, and made monumental discoveries using them. Among these are the moons of Jupiter, the craters and mountains on the Moon, the details of sunspots, and the fact that the Milky Way is composed of vast numbers of individual stars. mypascoconnect

 

[Pogo]

Gravitational Lansing does not produce the really cool image like looking at the moon or Jupiter in a good scope: Ooh, Ahh! A foreground galaxy can magnify a background galaxy in three or four stretched out arc-like magnified images one can get a spectrum from it after subtracting the spectrum of the foreground galaxy. The Sun, Jupiter, etc. would be so bright it they would overwhelm the background light. And whatever there is must be in direct line, we can’t move them around to targets.

 

[Helio]

I'm curious how hard it will be in tracking the object. Even if you move the telescope to get alignment to target, at > 1 billion magnification, won't it be incredible hard to track it long enough to get an image of it.

At 1 billion times in magnification -- I think they mentioned 100 billion times might be possible -- the "apparent" speed of the object will be more than 100x faster than light! [Not a violation of relativity since it's apparent.]

 

[Pogo]

At 10^9 magnification, atmospheric seeing must be terrible!