Re: ccd camera projects ? where ?

Jan Panteltje wrote:
On a sunny day (Tue, 03 Feb 2009 01:18:03 GMT) it happened Jon Kirwan
<jonk@xxxxxxxxxxxxxxxxxxx> wrote in
<eh6fo49uo8ghl8p89v7qqqcrhi6a5uf60t@xxxxxxx>:

Here is one of the better pages on this subject:
http://www.neurogy.com/kevin/NikonSpec/KC_Spectrometer.html

(I'm not sure what to expect butchering my DVD like that. I'd worry
about stress-defects being generated and although the entire DVD is a
bit largish it is very nice to design a system [as I have here] where
I can toss away one DVD and drop in another without a moment's effort
involved. It's a rigid and precise arrangement without wobble or
flexure pressures, yet I can remove the disk and replace it without
much effort. However, I'm going to take a crack at that -- pun
intended -- and see how that works out.)

I have a CD or DVD ( forgot what it was) glued to the front of a PC,
covering the harddisk slots.
Here it shows the fluorescent light spectrum:
ftp://panteltje.com/pub/fluorescent_light_spectrum_img_0874.jpg
those are the narrow green and purple lines.

The wide strong green bands is the daylight, coming in through a window on the side.
Thought it looked nice.
No deeper analysis happened.

You can actually do better than that with just a CD. At glancing incidence the CD behaves like a hologram of a slit and you can fairly easily see the more prominent Fraunhofer lines in the solar spectrum.

Details of the required geometry on Maurice Gavins page:
http://home.freeuk.com/m.gavin/solaspec.htm

It is one of the better uses of shovelware CDs (aluminium coated ones).

I use some of those DVDs (the coasters basically) as decoration too.
The Canon A470 CCD (not CMOS) camera has no problem with the colors.

If they are going to go wrong at all in colour rendition it will probably be along the line of purples. Flesh tones have to be right.
Early digital cameras had quirky response to monochromatic light. My first Kodak DC-120 was freaked out by a pure monochromatic red narroband H-alpha image. I think it relied on the green channel to determine the automatic exposure.

NB colour film has a dead spot in the mid green OIII emission line which is why old photos of nebulas are pink and blue on photographs but green to the visual observer with a big enough scope.

Regards,
Martin Brown
.

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