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Old 19-02-2008, 04:15 PM
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Article: Mono vs One Shot Colour (OSC) CCD's

Hi all

Dietmar has written a very interesting article regarding Mono vs One Shot Colour (OSC) CCD's.

You can find it from the IceInSpace Projects & Articles section, or by clicking on the link below:

Mono vs One Shot Colour (OSC) CCD's

Thanks to Dietmar for submitting the article to IceInSpace. If you'd like to contribute an article or review, please Contact Me.

Last edited by iceman; 26-02-2008 at 04:06 PM.
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Old 26-02-2008, 04:06 PM
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Article uploaded.
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Old 26-02-2008, 05:12 PM
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Quick comment/question: I understand the argument when it comes to photographic use, but how about photometry/astrometry? If you wanted the same resolution from a OSC as a monochrome CCD for positional or magnitude measurement, you're not likely to get it, are you?

I suppose, given a sufficiently bright object you could measure position using raw data prior to debayering, but I wonder how accurate magnitude determination would be on a OSC camera, especially as visual magnitude falls off? IE, to what magnitude could you accurately measure visual brightness within, say, 0.1 mag, when a bayer matrix is present? I guess these figures will be specific to a given sensor chip, but I suspect that even the current generation of OSC systems is of semi-limited scientific use (depending of course on one's definition of "Scientific")?

Regards,
Eric
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Old 26-02-2008, 05:41 PM
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Hi Eric
From what I understand , any sensor which uses anti blooming is not "good" enough for "scientific" work. So i would say that rules out any OSC sensor.
I think the implications are that you would not get an accurate brightness measurement over the region of interest due to the the photosites on the sensor reaching full well capacity on the brighter stars while the dimmer stars are only say at half well capacity.
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Steve
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Old 26-02-2008, 06:58 PM
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Theres a swag of Mono's that have ABG's as well, just make sure you order the correct sensor (NABG).

Theo.
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Old 26-02-2008, 07:18 PM
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bit to absorb there, ill read it properly later (saved it).if its as good as his images it will be informative.
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Old 26-02-2008, 07:33 PM
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Quote:
Originally Posted by skwinty View Post
Hi Eric
From what I understand , any sensor which uses anti blooming is not "good" enough for "scientific" work. So i would say that rules out any OSC sensor.
I think the implications are that you would not get an accurate brightness measurement over the region of interest due to the the photosites on the sensor reaching full well capacity on the brighter stars while the dimmer stars are only say at half well capacity.
Regards
Steve
This is not quite correct but it certainly makes it much more difficult. ABG chips become less linear as they reach over 1/2 full well. This complicates differential photometry but doesn't preclude it. There is a very good article at http://www.aavso.org/publications/ejaavso/v33n1/1.shtml
that discusses using a consumer grade ST7 for detection of planetary transits. They discuss the difficulty with the ABG type of chips.
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Old 26-02-2008, 07:54 PM
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Quote:
Originally Posted by Terry B View Post
This is not quite correct but it certainly makes it much more difficult. ABG chips become less linear as they reach over 1/2 full well. This complicates differential photometry but doesn't preclude it. There is a very good article at http://www.aavso.org/publications/ejaavso/v33n1/1.shtml
that discusses using a consumer grade ST7 for detection of planetary transits. They discuss the difficulty with the ABG type of chips.
Hi Terry
Good article you refer to.
I guess this is why I wrote good and scientific in quotation marks.
The article states.
1.The major challenge was to achieve long exposures.
2.Diminished well capacity does not help achieve long exposures
3.Differential photometry requires a large dynamic range which is enhanced by deep wells
4.Reduced well capacity and non linearity are definately problematic
5.Anti blooming reduces well capacity and introduces non linearity
6.Both these attribute are undesirable for photometry.

Any work around to these problems can only introduce more uncertainty and hence my statement regarding "good" and "science"
Regards
Steve

PS There is a subtle difference between differential photometry and searching for planetary transits.

Last edited by skwinty; 26-02-2008 at 08:06 PM.
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