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CCD, CMOS, pixel size, frame rate...


dawson
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I'm writing my signature for my posts and in doing so I just looked up the info on my modified webcam (Logitech Quickcam Pro 4000). It seems it can do max video resolution of 640x480 and a max frame rate of 30/second. A link Kim showed me suggests it has a pixel size of 3.4 microns and "bining" of 1x1.


 


So, I did a bit of looking around, and the better webcam lots of people use is the SPC900; that has a similar max video resolution but allows up to 90 frames per second and a pixel size 5.6 microns. My Canon 600D (CMOS) allows up to 30 frames per second and a pixel size of 4.31 microns.


 


Then I found this expensive CCD camera which has a pixel size of 5.4 micro but I can't find the frame rate info:


 


http://www.scsastro.co.uk/catalogue/orion-parsec-8300-astronomical-imaging-camera.htm


 


So, what are the crucial 'components' which result in better image quality? Pixel size, frame rate, overall 'megapixels'...?


 


I think it must be something else, as my Canon 600D must have a bigger sensor than the fancy CCD camera as it's 18 megapixels (I think).


 


Would changing my bottom of the range modified Quickcam for the SPC900 make much difference in my planetary imaging given my 127mm Mak aperture?


 


Thanks for any replies.


 


James


 


P.S. The sensor on my webcam has a few smears on. Try and clean or just ignore?


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Cheers Pat, that is what I was hoping you were going to say.


 


What about cleaning the sensor? I have noticed some streaking on the laptop when the camera is on (faint, but it's there), and I took the barrel off today and had a close look at the sensor and there are some streaks on it. I didn't want to just stuff a cotton bud with some alcohol down there before asking for advice :)


 


I feel much more confident with the software (Registax) side of things after watching that video Felix showed me the link to. I think I need to get better with my focusing, before my images will get much better.


 


James

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It's horses for courses.


 


For planetary imaging you want to beat the seeing and capture those odd instances when the atmosphere was stable.


 


Hence people use a high frame rate webcam shooting AVI and software to strip maybe 10% out of a 1000 frames that were undistorted.


 


Typically a CCD type is more sensitive than a CMOS type.


 


A 'proper' cooled astro CCD camera is for taking many single long exposure, several minutes in duration each.  These are stacked to improve signal to noise and hence image very faint oblects.


 


The problem with a webcam is that although it may do 90fps it has to start to compress the data at much above 10fps to get it down a USB cable to your PC.  More expensive planetary iamging cameras get around this.


 


However, you see where this is going, moneyyyyyyyy.


 


The SPC900 is a very good trade off.

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