There is another big drawback to using a "color" detector.
You are stuck with the filters the manufacturer placed on the front of
the chip. While fine for the daytime snapshot they do not have the
high efficiency of or color balance available in astronomical filters.
You could not do a Ha or OIII shot very well (yes you could put one of
those filters in front of a color detector but I believe the results
would be less than desired.

Of course if you have already selected a specific chip there may not
be a color filter option for it. You can only buy / get what they
make.

In general CMOS sensors do not offer as low as noise as CCDs.
Howerver the new Canon digital SLR cameras have CMOS sensors and dark
noise far below what my CCD based camera would produce (at the same
sensor temperature).

I wish you the best of luck on your endeavors.
Please publish the design if you get it to go.

Leonard

On Fri, 06 Feb 2004 09:09:18 GMT, "David Nakamoto"
wrote:

Color CCDs achieve their results by placing a matrix of color filters over
the sensor array. This cuts down on the sensitivity of the array,
increasing exposure times 2 to 3 times or more. It also reduces the
resolution, since every three to four pixels are used to recreate a single
color one.

CMOS does have higher noise, and less low light sensitivity.

The best color results are still from using a black and white CCD with a
color filters, taking one exposure per filter.


"Alain J" wrote in message
...
Hi

I want to build my own astronomical camera. I don't have decided which
I'll use. I want to put a color CMOS sensor but many web sites relates
that CMOS sensors are not very good (high dark level)
I've seen a color CMOS sensor with 1,3 Mpixel (1280x1024) at a very low
price (about $140).

For best performance, do I use a color sensor or B&W sensor ? In term
of sensitivy, dark noise which is the best (colour or B&W)?

Cordially

Alain