[Aavso-photometry] Linearity test puzzle

[Michael Newberry]

As a follow-up on this thread... I just looked at the paper you referenced. 
They're talking about a different kind of "ghosting" than I thought you 
meant. I agree with you that everyone interested in doing high-quality CCD 
work should look at the paper. Thanks for posting the link.

Regards,

Michael Newberry

----- Original Message ----- 
From: "Michael Newberry" <mnewberry at mirametrics.com>
To: "Wolfgang Renz" <w_renz at onlinehome.de>; "Michael Koppelman" 
<michael at isis.spa.umn.edu>
Cc: <aavso-photometry at mira.aavso.org>
Sent: Thursday, January 26, 2006 6:07 PM
Subject: Re: [Aavso-photometry] Linearity test puzzle


> Michael and Wolfgang,
>
> That is pretty old stuff, which is probably why it is not mentioned in
> modern CCD books. Ghosting is an issue with early CCD's that was caused by
> inability to flush the residual charge out. Nowadays the CCD's are almost
> perfect in CTE (typically 0.99999) and ghosting is not really a problem,
> provided it is working correctly. Two decades ago there were problems of
> CCD's not having a sufficiently high Charge Transfer Efficiency (CTE) to
> move charge during readout, and a bright star that saturated in a long
> exposure could leave a ghost image that took many minutes of flushing to
> remove. It also takes electronics working properly to transfer charge
> efficiently so, a modern CCD showing ghost images is either likely to be 
> on
> the verge of death or the electronics are not clocking the array in the
> optimal way.
>
> When I was in school in the late 80's, we had a GEC CCD on a 96 inch
> telescope that developed terrible ghosting problems during a slow approach
> to chip-death. It ended up ruining a number of people's thesis data.
>
> Michael Newberry
>
>
>
> ----- Original Message ----- 
> From: "Michael Koppelman" <lolife at bitstream.net>
> To: "Wolfgang Renz" <w_renz at onlinehome.de>
> Cc: <aavso-photometry at mira.aavso.org>
> Sent: Wednesday, January 25, 2006 2:07 PM
> Subject: Re: [Aavso-photometry] Linearity test puzzle
>
>
>> Thank you, I have that problem, too, and appreciate the info.
>>
>> Michael
>>
>> On Jan 25, 2006, at 1:38 PM, Wolfgang Renz wrote:
>>
>>> FYI
>>>
>>>
>>> ----- Original Message -----
>>> From: "Gary Neilson" <deepskyridge at yah...>
>>> To: <SBIG at yahoogroups.com>
>>> Sent: Wednesday, May 11, 2005 6:23 PM
>>> Subject: [SBIG] CCD Ghosting
>>>
>>> I found a paper describing this and have included a link to it.
>>>
>>> Armin Rest - Publications - Residual Images in CCD Detectors - 
>>> 02ghosting:
>>> www.astro.washington.edu/rest/papers/02ghosting.pdf
>>>
>>> It is a bit technical, however the introduction tells you most of what
>>> you need to know.
>>>
>>> As an aside, I have not found this mentioned in any of the most
>>> popular books on CCD astro imaging.
>>>
>>> It will change my image acquisition techniques.
>>>
>>> Thanks for all the reponses.
>>>
>>> Gary
>>>
>>> _______________________________________________
>>>
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>>> Aavso-photometry at mira.aavso.org
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>>
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>
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