misunderstanding concerning CCDs: correction, sorry!

There's something I think I have wrong concerning CCDs and I wanted to
find
out the correct answers. Say I have a webcam, which has an ICX098 CCD and
another camera with an ICX424 CCD. I want to image Jupiter with a C8 and
3x barlow ahead of the webcam and other camera. When the webcam/ barlow/
C8
combo are used, let's say that the diameter of Jupiter on the laptop
screen
is 3" across. Now, I remove the webcam and replace with the camera with
the
ICX424 CCD, making sure the CCD is the same distance as the webcam's.
What
will the image size be on the screen now?

The part I'm finding confusing is this: since the ICX424 covers a larger
pixel area than the 098 and also has a larger pixel size(?), I am assuming
the amplified Jupiter will not be the same size on the screen that the
webcam produces and will in fact be smaller with the 424 camera in place.
Am I wrong? Or is it that the 424 just covers a wider
area and the image size of Jupiter is still the same?

Finally, what benefit, if any, would there be with this combo system if
using just the 424? Would there be better resolution than the 098 offers
or
worse?

I know, lots of questions here, but would like to end my confusion once
and
for all!

Thanks,
John Edmund

"John Edmund" wrote in message
link.net...
There's something I think I have wrong concerning CCDs and I wanted to
find
out the correct answers. Say I have a webcam, which has an ICX098 CCD
and
another camera with an ICX424 CCD. I want to image Jupiter with a C8
and
3x barlow ahead of the webcam and other camera. When the webcam/
barlow/
C8
combo are used, let's say that the diameter of Jupiter on the laptop
screen
is 3" across. Now, I remove the webcam and replace with the camera with
the
ICX424 CCD, making sure the CCD is the same distance as the webcam's.
What
will the image size be on the screen now?

The part I'm finding confusing is this: since the ICX424 covers a
larger
pixel area than the 098 and also has a larger pixel size(?), I am
assuming
the amplified Jupiter will not be the same size on the screen that the
webcam produces and will in fact be smaller with the 424 camera in
place.
Am I wrong? Or is it that the 424 just covers a wider
area and the image size of Jupiter is still the same?

Finally, what benefit, if any, would there be with this combo system if
using just the 424? Would there be better resolution than the 098
offers
or
worse?

I know, lots of questions here, but would like to end my confusion once
and
for all!



Hi John,

Since both CCDs have the same number of pixels (640x480) the image of
Jupiter on the 424 chipped camera will appear smaller by 5.6/7.4 (The
relative size of the pixels in microns) ie it will cover fewer pixels and
each pixel will cover a bigger area. This means you will lose resolution
unless you increase magnification. (You would then be back to where you were
with the 098 chip in terms of resolution and field of view.)

HTH
Robin
--------------------------------------------------------------------------
Robin Leadbeater
54.75N 3.24W
http://www.leadbeaterhome.fsnet.co.uk/astro.htm
----------------------------------------------------------------------------
-