Did you try asking the photographer? :)

The EXIF data for the first photograph says:

• 459 seconds
• f/6.3
• 50 ISO
• 20mm focal length

It also says that the camera model is "O" (just a single letter), so I don't know for sure how accurate that EXIF data is. It also means we don't know anything about the sensor size, so the 20mm focal length isn't very useful except when calculating depth of field (which is clearly very large).

What EXIF data doesn't tell us is:

• whether or not there was a filter in front of the lens
• what the lighting was like (was the moon out? Did the photographer play a flashlight over the nearby rocks?)
• what post-processing work was done (e.g. colors or sharpening)

So I'd recommend:

• go out at night
• use a good solid tripod, and probably a shutter release cable
• take some very long exposures: 5-10 minutes
• bring an ND filter if you have one, maybe a CPL filter, too; if the pictures at 5+ minutes are too bright, try one of the filters.
• play around with different apertures, too. f/6.3 could be wide-open for that camera/lens (that picture could very well have been taken with a P&S camera that allows bulb mode or very long exposures (e.g. with CHDK)). If you have a fast lens or increase your ISO a lot you can get faster feedback to find the correct exposure, then when you have that figured out you can drop your ISO and use a narrower aperture to increase the depth of field.
• dress warm, wear gloves, bring some food & something (hot?) to drink. You don't want to have to give up early because you get uncomfortable.
• when you get home, don't look at the picture at its full size: resize it to 600 pixels wide or so and see if you like it.

Finally, here's a nighttime picture where I can tell you a little about how it was made:

Obviously the colors are very different. But this was 15 seconds at f/1.4 at ISO 100: that aperture and ISO setting gained me about 5 1/3 stops over the photo in question; 15 seconds * 2^5.3 = 591 seconds so my photo and the original actually have fairly similar exposure settings, although mine is a bit overexposed compared to the original (looking at the city lights). No filters. I used an okay tripod and shutter release cable, but there were a lot of strong wind gusts so I couldn't use very long exposures without a gust shaking the tripod a little. I don't really remember the moon being out, another picture from that evening shows a few stars visible through some wispy clouds.