I don't know of any CMOS sensor being used for professional astronomical
imaging, but they are used in related applications, like wavefront
sensors for adaptive optics, and for autoguiders. In these applications
they have distinct advantages over CCDs.
_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

I think they've already started using them on a small scale.  No 1G or
larger CMOS sensors at the back of professional telescopes yet.  But it
seems like CMOS might be good on satellites.

Quadibloc <jsavard@ecn.ab.ca> wrote in news:b29b5bcd-0942-4d1a-8d31-
b6ad39d29707@n33g2000pri.googlegroups.com:

Yes, the non linearity of the response of those small amplifiers remains an
issue.

From a digital photography point of view, definitely. The Canon D30
(launched in 2000 if my memory serves me well, not the later 30D) was
arguably the first widely available very good DSLR using a CMOS sensor.
Since that day, I believe all Canon DSLR used CMOS sensors.

For high speed video, CCD is definitely on the exit.

There are a few papers on SPIE exploring the use of CMOS technology for
astronomical applications.

Interesting.

Noise used to be one of the big problems with CMOS image sensors.

I was reading up on this to find out what the differences were.
Originally, CCD sensors were used because they had good performance,
while the first CMOS sensors gave very noisy images. Then the CMOS
design was changed, so that instead of simply one light-sensing
transistor per cell, a small amplifier was added as well. This
improved the performance with noise.

Today, CMOS sensors have two advantages - they can be read out more
quickly, and they have inherent resistance to "blooming". But CCD
sensors have the advantage that the sensor area covers nearly the
whole chip, and the advantage that since there is only one set of
electronics reading the charge from all the cells, the image is
inherently uniform.

Thus, CCD is still the traditional choice, although some say that CMOS
has caught up with it.

John Savard

Bit depth aside, photogs know from experience when something is "off."  For
instance, I know one photog who kept a Nikon D200 after buying a D300
because they just could not render the same skin tone quality with the
newer model.  No profile would do it.  This, despite obvious improvements
in other areas (like noise) going from CCD to CMOS.

Getting accurate color on ordinary images with any electronic sensor (or
film, for that matter) is an extremely complex problem- much more so
than for astronomical imaging. People are instantly aware of very subtle
color errors when comparing an image to reality (which you can't do with
most astronomical targets). So each camera maker uses their own
proprietary magic to manipulate the data into a realistic gamut. Some do
better than others, and some do better on some camera models than on
others.

There are differences between CCDs and CMOS detectors that manifest
themselves in different ways, but I don't see color accuracy as one of
those. Maybe on older cameras, where CMOS sensors were more limited in
dynamic range than CCDs, there could be some processing issues. But for
the last few years, cameras with CCDs and CMOS have both had similar
dynamic range- about 12 bits- which is more than enough to process and
reduce to 8-bit images.
_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

I heard this refrain time and again on the Olympus Dpreview group, that the
E-1 (CCD) had better colour than the NMOS sensors in the other Olympus
models.  This is the first time I've seen it mentioned on the Nikon group
(s).

http://forums.dpreview.com/forums/read.asp?forum=1039&message=30779163