Comparison of CCD chips

Link to colour camera:
www.starlight-xpress.co.uk/SXV-M25.htm

Link to monochrome camera:
www.starlight-xpress.co.uk/SXV-H16.htm

Thanks for the advice so far. Any further comments you may have would be appreciated.

At the mo, I'm thinking that the H16 might be the one ot go for, although it "only" has 30% QE at 650nm.

Seems to be very difficult to get a large ccd chip with small pixels and high QE (70-80%).

Cheers,

As a side note, what does 'QE' mean in this?

:oops:

As a side note, what does 'QE' mean in this?

:oops:

Quantum Efficiency.

Basically: When a photon of light hits metal it can knock an electron out. In a CCD when the photon knocks out the electron it then gets trapped by a positive charge.

If 90% of the incoming photons get converted to electrons then the device is said to have a QE of 90%. CCD's typically have peak QE values in the 90', photographic plates by comparison would have a QE of about 2%. In the case of film its the percentage of photons that cause the film emulsion to react.

The effect of knocking electrons out of place (the photoelectric effect) depends on wavelength not the intensity of the light. So you will see different values stated for different wavelengths. And so for different CCD's you will need to compose your colour image accordingly, eg. you may need a longer red exposure because the camera is not as sensite to red.

Once you have the electrons trapped, you still need to 'read' them out. This is another source of error with CCD's which is 'charge transfer efficiency'. QE just refers to the number of photons liberating electrons in the semiconductor.

hth

That helps, thanks Al!

Hi Michael,

I would want to see the spectral curves for the one shot colour camera. Assuming it is better then the mono (which it seems to be) then the colour camera would be the one I would go for.

Another point in its favour is the format, a wide screen format would look better on most people monitors these days

Later,

Jed.

Michael - here's a list Kodak chips of <10um pixel and at least 2048x2048 with > 50%QE

Kodak KAF-6303E Front-Illuminated 68% 3072 x 2048 9 µm
Kodak KAF-16801 Front-Illuminated 65% 4096 x 4096 9 µm
Kodak KAF-16803 Front-Illuminated 59% 4096 x 4096 9 µm
Kodak KAI-11002M Interline 51% 4008 x 2672 9 µm
Kodak KAI-4021M Interline 55% 2048 x 2048 7.4 µm

If you can go up to 15 µm, options get a little better:
Kodak KAF-09000 Front-Illuminated 69% 3056 x 3056 12 µm
E2V CCD42-40-1-368 Back-Illuminated 96% 2048 x 2048 13.5 µm
E2V CCD42-40-1-383 Front-Illuminated 50% 2048 x 2048 13.5 µm
E2V CCD47-10-1-371 Back-Illuminated 93% 1056 x1027 13 µm
E2V CCD47-10-1-373 Back-Illuminated 73% 1056 x1027 13 µm
Fairchild CCD486BI Back-Illuminated 96% 4096 x 4096 15 µm *
Fairchild CCD3041 Back-Illuminated 96% 2048 x 2048 15 µm

* I think this CCD imager (case plus chip) is somewhere around the $40K mark.

(Al - its rare that any CCD imagers are above the 90% mark - 70% plus is good. 90% plus is rare and very expensive in amateur circles).

Michael - you really need to figure out your average seeing and focal length(s). You can then calculate the best pixel size for your given focal length as half the average FWHM. Of course, you can alter your focal length with a reducer or Barlow.

If you want an imager to cover more than one focal length (and the FL's are very different) you'll have to trade off (or buy two imagers).

As regards the vendor's statements on darks etc, I'd be looking for documentary proof (eg dark frames) that support their statments. Though, I have heard the SE *do* have very low noise.

As for Colour or Mono - take your time and do the research...

FWIW
Dave