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View Full Version : New Images from the Ground are Better Than Hubble



Fraser
2007-Sep-05, 08:08 PM
As telescopes go, Hubble isn't actually that large; it's only 2.4 metres. But it has a huge advantage over the much larger ground-based observatories: ...

Read the full blog entry (http://www.universetoday.com/2007/09/05/new-images-from-the-ground-are-better-than-hubble/)

Fortunate
2007-Sep-05, 10:45 PM
Wow! That is nice.

cityonthemoon
2007-Sep-06, 01:55 AM
fantastic! I've been watching the Slow process of adaptive optics and it has been nothing but disappointment. This news should jump start many new large telescope projects and hopefully these new ccd's get into amateur telescopes sometime next year.

parallaxicality
2007-Sep-06, 11:03 AM
Man, before I die, amateurs could have scopes as good as Hubble in their back yards. This is what I love about astronomy. It just keeps going.

Mansie
2007-Sep-06, 02:23 PM
is there any reason why, in principle - if we had lenses and imaging equipment sufficiently without flaws, that an earth orbiting space telescope couldn't resolve say a newspaper headline on the surface of pluto? Or is there a natural limit to the resolution at a distance we could ever attain?

For instance : what is the smallest feature we might ever see on the surface of an atmosphere free planet orbiting Alpha Centuri (4.3 light years away),

antoniseb
2007-Sep-06, 04:27 PM
Or is there a natural limit to the resolution at a distance we could ever attain?
There are several limits, but the most obvious one is the wavelength divided by the diameter thing. This gives the limit, not how perfectly the mirror is figured. This is why Hubble can only give blurry images of the most distant galaxies it has seen. This is why Hubble can't get a nice clear image if any asteroids in the asteroid belt. etc. You could get an image showing a newspaper headline on Pluto (if such a newspaper were there) with an array of optical telescopes covering an area the size of the Moon's orbit around the Earth. Keeping these all aligned might be tedious.

Mansie
2007-Sep-06, 04:44 PM
There are several limits, but the most obvious one is the wavelength divided by the diameter thing..

Why is this an issue? The wavelength of light from a distant object (assume no doppler here!) might be the same as that from a more local object.... there's no mention of distance from source or angular magnitude in this equation

antoniseb
2007-Sep-06, 04:47 PM
Why is this an issue? The wavelength of light from a distant object (assume no doppler here!) might be the same as that from a more local object.... there's no mention of distance from source or angular magnitude in this equation
It's not a Doppler issue. Take a look at this wiki entry (http://en.wikipedia.org/wiki/Diffraction-limited). I think it explains it pretty well. BTW, the angular resolution needed to see a newspaper headline on Pluto is pretty extreme. (1014)

Mansie
2007-Sep-06, 05:23 PM
Thanks for the link - In fact the wiki article about 'Airy Discs' explains what I wanted to know. Which is: Optical resolution limits become apparent when the angular difference between any two objects approach a theoretical minimum because of interference issues.

This minimum angle of resolution is proportional to a constant / diameter of the appature. So if you want a higher resolution you need a bigger appature.

Thanks

markg85
2007-Sep-06, 07:32 PM
This is really awesome!

And correct me if i'm wrong but does this also mean that you need 20x the exposure time? (20 images/sec, 1 is good BUT with a low exposure time..)