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# What are CCDs? watch

1. Charged couple devices with high QEs , high linearity, but what actually are they? how do they work?
2. (Original post by mik1a)
Charged couple devices with high QEs , high linearity, but what actually are they? how do they work?
http://collections.ic.gc.ca/satellites/english/function/reconnai/charge.html
3. Thanks, that explains it a bit.
4. (Original post by mik1a)
Thanks, that explains it a bit.
Basically, when light hits the pixels, the silicon divisions electrons are released and a current is produced...
5. Do you know the size of a pixel?
6. (Original post by mik1a)
Do you know the size of a pixel?
Based upon my book an array of 2048 by 2048 is 3cm by 3cm...
7. So roughly 10 micrometres? photographic emulsions I got to be 1 micrometer on average, is this right?
edit - sry for all these questions, but there's a gaping whole in my astrophysics notes...
8. (Original post by mik1a)
So roughly 10 micrometres? photographic emulsions I got to be 1 micrometer on average, is this right?
edit - sry for all these questions, but there's a gaping whole in my astrophysics notes...
Same here with my darn teacher....this is my research work...think you're right if i can remember correctly photographic emulsions are smaller by a factor of 10....Check it out with Elpaw!!!
9. Another question,

how do you measure the parralax angle of a star so that you can work out its distance? What angles do you measure? Surely not the star to the sun, the sun would be too bright and too large. So what angle do you measure the nearby star's position against?
10. b0bsprrsa0r
11. You measure the angle from where you are on earth to the star, then 6 months later, you measure the same thing. The difference is the parallax angle.
12. What do you mean "from where you are on the Earth"? You mean the angle you need to look up from horizontal to the star?
13. Someone help me...
14. (Original post by mik1a)
Someone help me...
Hmmm, sorry, it appears i was talking crap.
My astrophysics notes are a bit thin too.

Anyways i just looked it up here. Go down to the pictures half way down.
15. Thanks, that's quite helpful, but I still don't understand what angle you measure the star's position against. Do you just find the star in the summer and the winter and measure the angle between them? (see attached image)

Maybe I'll ask my teacher, I understand it's hard to describe in words.
Attached Images

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