It's my understanding of observational astronomy that the size of a telescope limits its effective angular resolution, which is why scientists needed to use radio telescopes all over the globe to look at the M87 black hole and Sagittarius A\*.

For the sake of convenience, let's define a "good picture" as at least 100-by-100 pixels, and assume that all neutron stars have a diameter of 20 km. With this assumption, the nearest known neutron star is [PSR J0108−1431](https://en.wikipedia.org/wiki/PSR_J0108%E2%88%921431), at 424 light years away. This gives our neutron star an angular diameter of $2.9\times10^{-13}$ degrees, so the image would need a resolution of $2.9\times10^{-15}$ degrees per pixel. How big would a telescope need to be to see this accurately?