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SALT Telescope First Light
carnun writes "On the 1st of September, 5 years after ground breaking, the SALT Telescope released their first light images to the public. Yesterday one of these images was even displayed on NASA's Astronomy Picture of the Day website. The Southern African Large Telescope, built in South Africa, is the largest telescope in the Southern Hemisphere and (depending on how you define it) the equal largest telescope in the world, but built at a budget of only $30 million, about a tenth cheaper than its nearest competitor. The official opening of the telescope is scheduled for the 10th of November, but scientific observations are already a regular occurence. (Disclaimer: I'm the software engineer responsible for the main telescope server.)" Perhaps as an added bonus carnun could even be persuaded to participate heavily in the discussion. Either way, sounds like a cool project to be a part of.
Check the MirrorDot page, the original server is already smoking...
-- It's always darker before it goes pitch black.
It is based on the diameter of the primary mirror (~10m for SALT). The equal is the prototype which SALT is based on, the HET in Texas (I think). Resolution depends on diameter so it would also have the best resolution, but the Earth's atmosphere tends to distort things too much. This is why the Hubble Space Telescope (which is a mere 2.4M) is so valuable - no atmospheric disturbance.
However, having a giant mirror means that the telescope can observe faint objects in less time than anything in space at the moment, so can take much higher resolution spectra.
The actual telescope can't use the whole mirror at once because of the design. The telescope only moves in azimuth, which saves a huge amount of cost but means that only a small part of the mirror is used at any one time. As the target rotates around the sky the area on the telescope moves across the mirror to allow longer exposures.
SALT also has very high sensitivity to short wavelengths (blue/UV) which is probably the best of any large telescope, or at least close.
Usually comparisons are based on mirror diameters, so SALT is roughly equal to Keck One or Two, the 10m mirrors on Hawaii. But if you're looking for sharpness of image, then you might be more interested in baselines, where interferometry allows configuration of multiple mirrors to achieve sharper images (by cancelling out interference and unwanted signals), such as the VLT in Chile. Baselines at the VLT can reach 200m, which makes the 10m mirror not quite as impressive.
To put it in slashdot-friendly terms, you shouldn't just compare processors based on clock speed, because different processors may be optimized for different purposes. Mirror size is kind of like clock speed.