Space: The Final Frontier

[gtb1943]

Yeah I remember making this thread, and then I saw the date and couldn't believe that it was 7 years ago. Just blows my mind where the time goes these days.

and the older you get the worse it gets

 

[YosemiteSam]

After seeing images from Hubble and James Webb. Can a ground telescope be all that impressive?

Yes! Actually, space based telescopes used to be what amounts to a cheat-code for astronomical imaging compared to ground based telescopes. (you just couldn't compete with Hubble lol) That has changed with technology over the last few years.

The definitive game changer for ground based astronomy is Adaptive Optics. Instead of trying to look through the turbulent atmosphere, an adaptive options system uses lasers calculates exactly how the atmosphere is distorting incoming light and physically undoes the damage in real time using deformable mirrors.

When that first came out, I was highly skeptical, but it's now use use all over the place and its ubiquitous (well, depending on the mission requirements anyhow) with large grown based telescopes.

Another thing the ground has over space based telescopes is what can only be described as brute force. Hubble's mirror is about 2.4 meters wide and Webb (JWST) is 6.5 meters wide. On the ground, we have the VTL (Very Large Telescope) mirror at 8.2 meters, Keck in Hawaii that is 10 meters wide and then even the ELT (Extremely Large Telescope) that is 39 meters across!!!

Keep in mind that your ability to resolve details is physical linked to the aperture of the telescope (ie, how wide the mirror is) So, these ground based telescopes can technical resolve more details than the smaller space based telescopes. (Hubble and JWST)

The other thing we use (We've almost always used it for planetary imaging) is what some people refer to as "Lucky Imaging". In astrophotography, it's common to take very long exposures to get as much detail as possible. For instance, you take a (36) 5 minute exposure and merge them into a single image that is basically the results of staring at the object for three straight hours. It is this reason why when you look through even super large telescopes. The galaxies look like a blurry cotton ball rather than the stark structures you see in high quality astrophotography.

In what is called the lucky imaging. Instead of taking long exposure photography where atmospheric distortions will blur the image. They take ultra fast video sequences of over 100 frames per second and we discard the ones blurred by the atmosphere and keep the sharp images that remain and merge them into a single long exposure image. This creates a perfectly crisp frame, but you loose some of the time it took to get the image. If you do this for long enough and get enough quality crisp images, you can produce images that are similar to space images.

Now, all these technologies don't remove the need for space based telescopes because there are still things that we cannot control like the atmosphere blocks some wavelengths of light such as ultraviolet, x-rays and the infrared spectrum. If the light never makes to the telescope, you can't really image it. The other issue is that the Earth itself radiates heat in the infrared spectrum and this terrestrial light ends up getting recorded in the image. A space based telescope does not have to contend with these two issues.

 

[YosemiteSam]

and the older you get the worse it gets

Every negative created by aging seems to accelerate once you hit your 50s. lol