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Infrared Astronomy


badgerchap
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Depends what you mean by infra-red really...

+ 650nm-950nm is redder than you can see with your eye, but you can still detect it with a CCD. Perfectly possible from the midlands... Some people call this infrared, but most professionals don't these days.

+ 1000nm-5000nm needs a different type of detector technology, a liquid-nitrogen cryostat (at least), and about $100,000 to buy the detectors (if you can convince the Americans to sell you one). Still possible from the midlands, if you choose the right bands between the water absorption.

+ 5000-20000nm needs an even more different type of detector, a liquid-helium cryostat, and even more $ and hassle getting the Americans to sell you one, and a very high (>3000m) mountain.

+ >20000nm (like the IRAS(?) image euan showed) you need to be in space.

Edited by FraserClarke
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Ordinary CCD cameras have a response that rolls off essentially to zero by 1100 nm. Nevertheless the near IR is useful for planetary & lunar imaging - the seeing is steadier - I quite often use a 742 nm IR pass filter (Astronomic Planet Pro); such a filter also darkens the twilight/daylight sky quite a lot. Might be useful for luminance frames on twilit (summer) / moonlit nights too. IR pass filters are very good at blocking all forms of light pollution except tungsten / halogen lighting.

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+ 1000nm-5000nm needs a different type of detector technology, a liquid-nitrogen cryostat (at least), and about $100,000 to buy the detectors (if you can convince the Americans to sell you one). Still possible from the midlands, if you choose the right bands between the water absorption.

Yeah, for spectroscopy there are atmospheric windows in the H and Ks bands (1.6 and 2.1 microns respectively) have limited telluric contamination - I do a lot of work in this area on stars near the galactic centre where the optical spectrum is very attenuated by dust/gas in the line of sight.

The ISAAC instrument on the VLT uses a Rockwell 1024x1024 pixel Hg:Cd:Te detector (for longer wavelengths there's a In:Sb detector), which can be used in imaging and spectroscopic modes. The techniques are somewhat different to 'normal' visual imaging/spectroscopy though.

Edited by Ben Ritchie
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