Observatory aperture does not win?

I just stumbled upon this article on my break and almost fell out of my chair! According to the article, the following scopes can see down to the following magnitude:
http://skyandtelescope.com/printable/howto/basics/article_241.asp

100-inch (if I recall) Hubble: 30th magnitude
200-inch Mt. Palomar: 20th magnitude
[4-inch TV-102: 13th magnitude] I add this for scale ;-).

I've been to Mt. Palomar Observatory once in the early 80s and it's very high up. How can the HST with 1/2 aperture see much dimmer than the 200" even if it's in space? No can be, right? Even if the 200" has to see through some air. I've even now accepted that "aperture wins and win absolutely" :-(, until now!

Is the S&T article in error? But if this is correct, then my 4" TV-102 would be able to see down to 17th magnitude or dimmer piggy back on the HST!

Thanks,
Ron B[ee]

Hubble can do better than Palomar 200" for small targets
(stars, etc., anything that looks stellar) due to
the atmosphere. On Earth, light from a faint
stellar target gets mixed with about one square arcsecond
of sky background light, which makes it hard to see.
For Hubble, stellar targets get mixed with only about
0.003 square arcsecond of a fainter sky background --
thats advantage gained by taking away the atmosphere.

The 20th mag number for Palomar 200" isn't for
CCD; you can get down to 24 - 25 magnitude range
with 200" and CCD if you try hard enough.

It is sobering to think that the *resolution*
of Palomar 200" is about the same as your TV102
lightcup, due to the atmosphere. Both have resolution
around 1 arcsecond. Though, of course,
Palomar collects alot more photons.