REVISION DATE: 07-Jun-2012 10:37:16

Mike wanted to check the different darks collected. Background, Dark and Ambient. Below are the definitions of the different darks from the Documentation. They all look good to me! The first frame (which is always low) is removed before the data is meaned. The graphs below are the mean of all frames (minus frame 1) for Track 7. I removed the first 10 pixels because the are so low you can not see the shape of the darks.

I should mention that the files which were marked Background and Dark all have the shutter control set to 2. The ambient had shutter control set to 1. You can see this on the data listing page. The reading program says there are three settings for the Shutter control (Normal, Disabled Open, Disabled Close), I don' know which one is a 2 or a 1. According to the descriptions below the Darks should be on Normal and the Background should be "disabled" (closed or open is not mentioned). So the Darks and Background should have different shutter control number but they don't. No idea what this means.

Background is what we get with the CCD camera closed (CCD setting is “disable closed”; the camera shutter is closed during “acquisitions”)

Dark is what we get with the CCD shutter operating normally but with the fiber optic coupled channels “lens capped”. With the present configuration (Romack input bundle), Dark is made by capping the ends of the fibers. In the final configuration (foreoptic, fiber/beamsplitter/fiber/shutter/fiber) this could mean we cap the entire system at the foreoptic or close the shutter.

Ambient is what we get with the CCD shutter operating normally, the fibers or optical system uncapped, but the light source is blocked – either the lamp is off or the sphere lamp is shuttered or there is an on axis baffle of some sort. An input fiber connected to a LED stability source with the source off is Ambient datatype.

Figure 1

Figure 2