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Incredible Images of the Sun
shelterit writes "A new swedish telescope facility in La Palma uses a new technology to remove the blurriness of the atmosphere to snap new and astonishingly sharp images of the sun. Want to have a closer look at the surface of it? Reminds me of paintings I did as a kid."
The filaments' newly revealed dark cores are seen to be thousands of kilometers long but only about 100 kilometers wide. Resolving features 100 kilometers wide or less is a milestone in solar astronomy and has been achieved here using sophisticated adaptive optics, digital image stacking, and processing techniques to counter the blurring effect of Earth's atmosphere. At optical wavelengths, these images are sharper than even current space-based solar observatories can produce.
I hold it, that a little rebellion, now and then, is a good thing. -- Thomas Jefferson
The technology used by this telescope to counter the effects of the atmosphere in measurements is called adaptive optics. This is the first application I know of for adaptive optics on a solar telescope.
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This technology has been around for awhile, and was first seriously developed by the military at the Starfire Optical Range
Recently it has been used in such telescope projects as the WM Keck Observatory and Gemini Project . I know AO is also used for measurement of eye aberrations, with projects being conducted at several Universities. For more information about Adaptive Optics, I suggest the Center for Adaptive Optics
My personal experience with AO was as an intern for Gemini this past summer. I helped write parallel code for a program that simulates current and future adaptive optics systems planned for the next generation of extremely large telescopes.
From my days doing Earth Observation Science (EOS) I recall that a lot of satellite imaging, whether astronomical or remote sensing, seemed to follow a de-facto standard of a 512 x 512 x 8bit image tile per channel on the instrument.
GIFs were often used because it is a very stable way of doing lossless compression at 8bit, stable as in almost any image program can read them.
This is not the case with TIFFs as there are a number of variants and options in the file format.
TIFFs are however a better medium for storage of composite images, either spatially or spectorally (montages or multichannel pseudo colour in english).
Due to its general lack of use as a data storage format most of the tools I used/wrote to proccess image data files generally did not have JPEG support or other common 'display' options as the file is regarded as data, not an image - its a subtle difference but explains the mindset.
When I published stuff on the web I'd run our raw large images through Photoshop to get pleasing images but compact file sizes.
It may not have occured for them to do this, and anyway they may regard this as publishing data for other interested parties to download and process themselves.
Increasing the aperture of a telescope has two effects:
More light is collected. (Since astronomical telescopes are usually used to look at dim objects this is normally considered an advantage.)
To reduce the diffraction effects and so increase the spatial resolution.
When observing the sun, the second of these is still required but the first is a problem. The sun provides too much light, especially in the infrared, to observe safely.
The solution is to place a filter over the front of the telescope which cuts down the amount of light entering the scope. This reduction generally needs to be of the order of 1:1,000,000.
Filters at the back end of the telescope, directly in front of the eyepiece/camera, are not safe. All the heat from the sun passes the scope through and is focused through this small filter. They can then easily crack or melt.
Safety notice: The only safe filters for observing the sun are those designed for the job. They are usually thin plastic, sometimes glass, with a metal coating on both sides. Always check the filter is firmly fixed in place and has no scratches or pinholes. It is this filter type which was used in the eclipse safety glasses a few years back. When observing by eye, with no telescope, binoculars or other magnification, welder's No 14 glass or fully exposed and developed black and white film negatives are also safe. (Not colour film or b&w film developed with a colour process - it is the deposited metallic silver used in the b&w process which provides the protection.) NOTHING else is considered safe.
You can get cooled CCD cameras, and the astrophotographical community has been using them for years. (Well, those than can afford them anyway.) The cooling is required to reduce the 'dark current' within the camera itself during long exposures, not to remove incoming heat.
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