If you only have a wide-field lens and find that a small sun in your photo is not good enough, you may consider trying to shoot flash spectrum together with the sun, if you can get hold of a diffraction grating. Inspired by the following, I may have a go at it this year.
http://forum.hkas.org.hk/viewthread.php?tid=2711
I did some search on the web to find out what flash spectrum is. When the solar disk is just obscured by the sun and the chromosphere is visible, the line spectrum from the chromosphere can be observed through diffracting grating. Theoretically, you can work out the elements on the sun from such spectrum. In fact, helium was discovered in this way on the sun, before it was found on earth.
After a while, even the chromosphere will be obscured and so the flash spectrum disappears.
The spectrum looks like the one shown here:
http://www.moonglow.net/eclipse/2006mar29/index.html
This morning, I had a trial on what I have at hand, which is a 17-40mm lens and a grating of 500 lines per mm (Don't have much choice in school). I simply hold the grating in front of the lens by hand. Although the grating is smaller than the lens, one can still get an okay picture.
With such bright object, exposure time was very short and so it was a handheld shot. The result is shown in the picture. At 40mm, the lamp and the 1st order spectrum fits within the photo, which is what I want.
May be I'll place the camera on an ordinary tripod for this, and start shooting from diamond ring at 3fps for about 10 seconds.
Finally, allow me to emphasize that this is done just for fun and so my set up is pretty simple. Also, the most important thing in an eclipse is to watch visually rather than to shoot. I am considering this simply because I have a friend to shoot with me, and I want to try something new this year, as well as the fact that I can borrow a grating.
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elephantrx178
- 星際雲
- 文章: 42
- 註冊時間: 週四 06 9月, 2007 23:18
It is a very cheap plastic one. Don't expect very high quality. As I said, it is just for fun (e.g. I don't expect to zoom in and see very sharp line spectrum!.)Wah!! 寫:Is the grating a glass grating, or a platic grating with blank glass?
Can you reseve one for me? Thanks~
If anyone wants to join the group order, please PM or leave your name on this thread.
Cheap plastic grating
Hi,David 寫:It is a very cheap plastic one. Don't expect very high quality. As I said, it is just for fun (e.g. I don't expect to zoom in and see very sharp line spectrum!.)Wah!! 寫:Is the grating a glass grating, or a platic grating with blank glass?
Can you reseve one for me? Thanks~
If anyone wants to join the group order, please PM or leave your name on this thread.
In fact, if you just like to experiment with such setup, get the CLEAR DVD disc from your DVD box (there is usually one each on the top and bottom when you buy a box of DVD disc) and cut a sector. The grooves will be part of a circle but it will serve the purpose for a trial.
PTS
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