[Aavso-photometry] Linearity test puzzle

[Michael Newberry]

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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