# Is there a telescope on board the ISS?

I am wondering if there is a telescope in or outside the ISS that has been used for astronomical imaging? I have seen here that there is already a Celestron telescope on board but it is only used for Earth observation.

• Hi Dean, is there any chance you'd consider accepting the answer to this, or your other question in Space SE? Just a thought, thanks! – uhoh Sep 22 '18 at 7:09

It is however just used to observe the Earth, and the reason for that is the orbital velocity of the ISS. Moving at almost $8km/s$, the view change with an angular velocity of 3.88 arc-degrees per second because the station rotates to keep the same side facing the Earth. If the ISS had instead stayed fixed relative to the stars, like the Hubble telescope, you get the same problem with Earth observations. You can not simply do both.