Several years ago I backpacking in the Atacama desert in Chile. That's where a lot of telescopes are built because it's so dry. I stopped in one city and I tried to find an observatory through my hostel that took visitors but had no luck. Guess whatever tour was available wasn't popular enough. Has anyone had any luck in Chile?
I've toured several observatories in Chile (and had a blast doing so.) That being said, I studied astrophysics and spent a few months doing astronomy research in Chile, so I wasn't really taking public tours or anything.
I visited La Silla last December[0] whilst traveling around South America. It was a few hours' drive up from La Serena, along some quite windy roads, but definitely worth it. You have to book by email in advance.
One of the reasons that there wasn't much in the way of development of larger telescopes in the late 1970s and 1980s was the development of the CCD. Prior to the CCD, astronomers used photographic plates to take their images, and photographic plates have horrendous efficiencies. A typical photographic plate will only register a few percent of the incident photons. A CCD, however, has an efficiency very close to 100% (except at really low wavelengths). Almost immediately after its invention, new instruments with CCDs were built to be put on existing telescopes. [1] Because the efficiency was a factor of ~30 larger, it was as though you had quintupled the diameter of your telescope. There wasn't much of a reason, then, to invest in huge new telescopes when you could effectively have a huge new telescope just by building a CCD detector.
Also, as a graduate student at Ohio State I would be remiss if I neglected to mention that the Large Binocular Telescope was originally planned to be built at the same time as Keck. It was originally conceived to be larger and with OSU providing a large fraction of the funding. OSU's president, Gordon Gee, cut funding for the project in the early 90's, however, which threw the project into disarray. Most of the faculty in the Ohio State astronomy department resigned in protest which is why Ohio State has had a department with relatively young faculty. Due to problems funding the project and technical difficulties (putting two very large mirrors on a common mount turned out to be harder than anticipated), the telescope had to be scaled back and it only saw first light in 2005.
[1] As an aside, astronomy has been one of the major drivers of improvements in CCD technology. CCDs in consumer devices are generally used in photon-rich environments and the users can tolerate a lot of noise in their images. Astronomers, however, demand very low noise and use their CCDs in photon-poor environments, and the production of these kinds of devices has required major improvements in CCD technology.
If you have a DSLR you can get pretty good results with that. You will absolutely have to learn how to use a stacking program for great images as qwerta said. If you could afford it you would want a super chilled (80K is common due to LN2 cooling) detector for low noise.
For CCD technologies, I work peripherally with the LSST camera group developing and testing the shutter and sensor. The sensor is going to be 3.2GP.
Also, the K foundations together (Keck and Kavli) are pretty amazing foundations as far as astronomy and other pure science (especially not commercially beneficial) sciences go.
Do you mean building a 5 meter wide oblong mirror instead of a 5 meter wide circle? That might be easier but wold be a far inferior telescope. The amount of light collected goes as the area of the mirror. If you're suggesting keeping the same area but being more oblong, then I don't see any advantages.
I did mean the same area. The advantage is that since it is longer it has a larger footprint.
Meaning more support, which to me seems easier to build (mechanically, don't know if the optics themself will be more complicated - that was my question).
I think a big challenge would be that it would be much harder to grind the mirror. Round mirrors have the advantage of being somewhat close to a parabola, so you can spin them and use gravity and then just refine from there. The optics also get more complicated.
One key thing that I think would help you here is that the hard parts of building a telescope are the mirror and the instruments, not the mechanical telescope to support it. Supporting a ten meter wide mirror is not too hard compared to making a near-perfectly ground mirror that is ten meters wide or building top shelf instruments to collect and study the light. It's not cheap or anything, but it's not really what's holding back telescopes. You can see this in the new generation of 20-30 meter scale telescopes with multi-mirror designs. The GMT uses several 8 meter mirrors because we can't really make useful mirrors larger than about 10 meters.
Related question: is it possible to build cylindrical reflectors (more precisely, two dimensional reflectors with a constant parabolic profile along X axis), gather the light into a linear CCD array and do the Y axis focusing in software?
Reason: this will allow us to fabricate mirrors either by bending planar materials or by using a grinding tool that has the shape of the full parabolic cross section. Theoretically this should be a lot cheaper than the grinding methods we use now.
That's pretty impressive. Given the size and importance of the mirrors, I wondered how they actually clean them. Came across this:
https://www.youtube.com/watch?v=CkV8RRRu7gE
The GMT telescope has mirrors 8.4 meters across with a fault tolerance of 19 nanometers. If you were to scale that mirror up to the size of Earth, the biggest imperfection would be just 2.8 centimetres high. That is amazing.
For another perspective on that size, it's a mirror between 4 and 5 times your height, to a fault tolerance of less than 200 hydrogen atoms (or about 60 SiO2 molecules., if I have my calculations right)
Disappointed the article didn't discuss the pros/cons of earth-based telescopes versus space based. Why build earth based telescopes when you have the atmosphere in the way?
It's way cheaper to build ground-based telescopes than it is to build space-based ones (and you can easily upgrade it too). Thanks to advances in adaptive optics you can now get most of the properties of space-based telescopes with ground-based ones (even existing ones).
One major limit here is what the atmosphere absorbs.. so for X-Ray, Far-IR, etc. you will still need space-missions.. that's where the focus is now set mostly at ESA/NASA/etc..
Did you check out the SVG comparing telescope sizes that batbomb posted? The short answer is "you can build 'em a lot bigger" (or maybe "you can build 'em a lot cheaper" if you prefer).
These telescopes are gigantic and simply dwarf the James Webb Space Telescope. Adaptive optics have come a long way, too.
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[ 3.3 ms ] story [ 36.9 ms ] threadhttp://www.eso.org/public/about-eso/visitors/
[0] https://twitter.com/marcosscriven/status/409787993617342464
http://www.archello.com/en/project/eso-hotel-cerro-paranal-c...
It was used in the James Bond movie "Quantum of Solace".
http://upload.wikimedia.org/wikipedia/commons/c/c5/Compariso...
Also, as a graduate student at Ohio State I would be remiss if I neglected to mention that the Large Binocular Telescope was originally planned to be built at the same time as Keck. It was originally conceived to be larger and with OSU providing a large fraction of the funding. OSU's president, Gordon Gee, cut funding for the project in the early 90's, however, which threw the project into disarray. Most of the faculty in the Ohio State astronomy department resigned in protest which is why Ohio State has had a department with relatively young faculty. Due to problems funding the project and technical difficulties (putting two very large mirrors on a common mount turned out to be harder than anticipated), the telescope had to be scaled back and it only saw first light in 2005.
[1] As an aside, astronomy has been one of the major drivers of improvements in CCD technology. CCDs in consumer devices are generally used in photon-rich environments and the users can tolerate a lot of noise in their images. Astronomers, however, demand very low noise and use their CCDs in photon-poor environments, and the production of these kinds of devices has required major improvements in CCD technology.
Also, the K foundations together (Keck and Kavli) are pretty amazing foundations as far as astronomy and other pure science (especially not commercially beneficial) sciences go.
Can you make an extremely long, but not very tall mirror? Seems like that would be easier to build.
Edit: I'm asking because I'm pretty sure it wouldn't be.
Meaning more support, which to me seems easier to build (mechanically, don't know if the optics themself will be more complicated - that was my question).
One key thing that I think would help you here is that the hard parts of building a telescope are the mirror and the instruments, not the mechanical telescope to support it. Supporting a ten meter wide mirror is not too hard compared to making a near-perfectly ground mirror that is ten meters wide or building top shelf instruments to collect and study the light. It's not cheap or anything, but it's not really what's holding back telescopes. You can see this in the new generation of 20-30 meter scale telescopes with multi-mirror designs. The GMT uses several 8 meter mirrors because we can't really make useful mirrors larger than about 10 meters.
You might also find the Large Zenith Telescope interesting: it has a spinning liquid mirror! http://www.astro.ubc.ca/LMT/lzt/index.html
Reason: this will allow us to fabricate mirrors either by bending planar materials or by using a grinding tool that has the shape of the full parabolic cross section. Theoretically this should be a lot cheaper than the grinding methods we use now.
One major limit here is what the atmosphere absorbs.. so for X-Ray, Far-IR, etc. you will still need space-missions.. that's where the focus is now set mostly at ESA/NASA/etc..
These telescopes are gigantic and simply dwarf the James Webb Space Telescope. Adaptive optics have come a long way, too.