Tuesday, February 21, 2012

Stray light in high-med at 13.7 microns

I looked at data comparing looking at the room at the Q-branch in high-med mode with the same setup looking at the lens wheel dark.  The data were 16 destructive coadds with 110 ctdelay (3 seconds).

I rotated the image using IDL rot() to get orders to mostly run along columns.  I then plotted rows 200-800 normalized to ADU/seconds and as a fraction of the row peak (actually, row 98th %ile).  Plot is below.


The short answer is I think we have scattered light at this setting of <=25 ADU/sec.  We'll enter this into the table.
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1 comment:

MJR said...

I looked at the 18a filter scan. Note that there was no "dark" to compare this with, so I just subtracted off a reset value which could include scattered light.

Comparing a high and low flux image, the absolute count range between orders was similar at about -50 to 50 ADU/sec level. This contribution is probably NOT due to the incident light scattering off the gratings.

There is also a trend where images with more light tended to have "reset" values that indicated more scattering.

Sounds like we've got more work to do on scattered light getting to the detector. We could also make a better test next time comparing blanked off detector with selected "looking at light" settings.

5/10/2012 2:35 PM

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