DECam Known Problems

CCD N30

One of the DECam science CCDs, N30, shows a very low full well and poor charge transfer efficiency.  Observations taken with N30 are likely not going to be scientifically useful.  Luckily this CCD is located at the edge of the focal plane array (see focal plane array here).  Diagnosing the problem and finding an appropriate fix is ongoing.

Bright Saturated Star Electronic Issues

Below is what happens when a bright saturated star falls in your CCD. 

This may be caused by an overflow along the serial register.  Every DECam CCD appears to exhibit this behavior.  Further investigation and finding an appropriate fix is ongoing.

Non-linear Crosstalk

Non-linear crosstalk is reported when source exceeds 60k ADU (260k electrons) for CCDs with negative crosstalk coefficients (about half of the CCDs).  The crosstalk correction overcorrects the negative value.  Further investigation and finding an appropriate fix is ongoing.

Low light-level non-linearity

There is evidence that 18 of the DECam CCDs exhibit low light-level non-linearity.  More information can be found here.  Further investigation and finding an appropriate fix is ongoing.

Finding the mouse

The mouse pointer is really easy to loose track of in those eight monitors. You can now get some help locating it by pressing the ctrl key on the keyboard; this will make some concentric circles radiate out an inch or so from the pointer. This can be enable/disabled through the toolbar's System dropdown -> Preferences -> Mouse. This brings up a new window with two tabs; the "General" tab has a "Locate Pointer" section with a check box to turn this behaviour on and off.

GUI Timeout and Freezes

Eventually the GUIs on the observer1 console will run out of resources (most often memory) and they will crash or their response will become sluggish. The most dangerous situation are stale displays - the GUI's look fine but they are not updating. It is recommended to refresh each GUI occasionally. Note that it is safe to restart all GUIs without interrupting the SISPI instance.