[dylan604]

Yes and no. Yes, if there are clouds, optical telescopes can't see through them. That's why the really big scopes are built high up in the mountains above clouds. They are also being built in the dry desert air to prevent issues from humidity. With AO (adaptive optics), any atmospheric distortion can be compensated and removed from the images. So in some cases, we get better images from ground based scopes than space based. The size of the primary mirror is a huge factor. This image is a favorite of mine that shows the size of various famous telescopes[0]

It's also possible to build larger telescopes on the ground. It just makes more sense and cents to build on the ground than into oribit. However, something like James Webb needs to be in space due to the type of research it is doing. Also why it is getting sent so far away rather than a closer orbit like Hubble.

[0]https://i.pinimg.com/originals/96/23/15/962315f7e4d4f4191de2...

[godelski]

While I agree with this, I do think easy access to space also enables much larger telescopes in space. It would greatly decrease the cost of JWST. Though not enough to still compete with size/$ (GMT is planned at $1bn and JWST is $10bn, and GMT is like 7 JWSTs in size).

[dylan604]

What I would sci-fi utlimately love is the combination of both. Putting permanent bases on the moon, and then building whatever the sciencey word for lunar telescopes. They get the benefits of no atmosphere, and the benefits of being on the "ground" so things can be updated/fixed compared to just floating in space.

[LargoLasskhyfv]

Makes no sense to me. Given you'd have the capabilities to have bases there, you'd also have the capabilities to fix stuff floating in space effortlessly. Btw. ground can shake or vibrate, which is no benefit at all.

edit: also electrostatically charged, abrasive dust particles.

[LargoLasskhyfv]

https://commons.wikimedia.org/wiki/File:Comparison_optical_t...

[robscallsign]

Thanks for the reply, that image is pretty compelling,

It seems that space based telescopes could be substantially larger than Earth based telescopes, based on not having to build a structure to support their weight then?

[dylan604]

Sounds like a good idea, except we have a hard time getting really large things off the ground. If you notice the size of the James Webb with its unfolding primary is still really small compared to other terrestrial based mirrors. It's mind boggling to look at the size of those mirrors, and then easily missed is the comparison to the former dish at Arecibo. Arecibo doesn't even fit in the image and is just an arc that looks like the background.