[Aavso-photometry] Linearity test puzzle

[Wolfgang Renz]

FYI


----- Original Message ----- 
From: "rdcrisp" <rdcrisp at earthl...>
To: <SBIG at yahoogroups.com>
Sent: Wednesday, August 04, 2004 3:17 PM
Subject: [SBIG] Re: ST10XE Image Persistence..ghosting?

--- In SBIG at yahoogroups.com, "Paul K" <paul at p...> wrote:
> To deal with this I now routinely raise the chip temperature to 
> ambient after a bright-star focusing run, and then lower it again 
> to the desired set point. This seems to get rid of the ghost 
> completely, 

That's what I do too if it happens to me. I try to avoid bright stars 
if possible but it doesn't always work.

I don't like raising the temp and then lowering it because it takes 
extra time and makes the bias drift around.



----- Original Message ----- 
From: "Paul K" <paul at pk.dar...>
To: <SBIG at yahoogroups.com>
Sent: Wednesday, August 04, 2004 2:05 PM
Subject: [SBIG] Re: ST10XE Image Persistence..ghosting?


Russ, there's a persistence of charge that seems to follow a really 
bright (over?)exposure. I've been using an ST10xme for a few months 
now, and I experience it almost every time I'm out when I first start 
to focus on a bright star.

As you've noticed, the ghosting goes away with time, but it also 
appears to be related to chip temperature: the lower the temperature, 
the longer it takes to fade.

To deal with this I now routinely raise the chip temperature to 
ambient after a bright-star focusing run, and then lower it again to 
the desired set point. This seems to get rid of the ghost completely, 
as long as ambient is +5°C or above. If I raise the set point to 
below 5°, it still seems to take many minutes for it to fade. Don't 
know what I'll do when the ambient falls below 5° -- probably use 
only really dim stars to focus on :-)

Regards,
      -Paul



----- Original Message ----- 
From: "Russ Durkee" <russdurkee at earthl...>
To: <SBIG at yahoogroups.com>
Sent: Wednesday, August 04, 2004 12:38 PM
Subject: [SBIG] ST10XE Image Persistence..ghosting?

Hello,

When imaging brighter stars or objects and then follow with a dark 
frame or move the telescope slightly, I notice a ghost image of the 
brightest stars still present on the following image or the dark 
frame.  These ghost images fade over time and only appear on the 
brightest objects.  I am using a new (purchased Nov 03) ST10XE  (not 
ME).  I do primarily photometry and this is a bit troubling.
  
I think I recall an announcement about this at one point, but I am 
not sure.

What is causing this?
Can it be corrected?
Does this happen in other cameras such as the ST8XE?  

 Regards,

Russ Durkee