WFI Linearity Performance |
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Nt/Nm = 1 + A1*Nm + A2*Nm*Nm + A3*Nm*Nm*Nm .....
Speed =FAST, Filter = i .
1024x1024 central regions in each CCD were observed at a range of exposure times. No overscans are available, so the images were bias-subtracted, making their zero level uncertain by +-1adu.10s exposures were combined to make a flat field to correct pixel-pixel varations. The flat field from each CCD was then independently re-normalised (so that flattened adu values in each CCD would reflect their raw normalisation).
Image statistics were obtained in the window (in IRAF format) [420:597,415:560] in each CCD. Exposure times for each CCD were made shorter by -22.0ms to account for the shutter timing error measured from the same data.
Plots were then made of counts vs exposure time to derive linearity corrections.
Note that all the corrections are very similar in form to those found on 25Dec00. In fact, with the exception of the A0 term for CCD4, all the fitted coefficients are very similar. However, the A0 term differences only correspond to a small arbitrary change in CCD gain, and so are not significant.
02FEB01 - Polynomial Linearity Corrections for WFI. CCD A0 A1 A2 A3 Residuals
(%)Max ADU
above biasUncorrected Non-linearity
< 0.5% below
(adu above bias)1 1 0 3.86e-12 0.4 52,000 36,000 Plot 2 1 0 3.18e-12 1.0 54,000 35,000 Plot 3 1 0 8.43e-12 0.9 42,000 24,000 Plot 4 1.02753 -1.6455e-6 1.7791e-11 0.8 52,000 <10,000 Plot 5 1 0 4.26e-12 1.3 44,000 32,000 Plot 6 1 0 5.93e-12 1.3 57,000 28,000 Plot 7 1 0 -5.50957e-11 2.39334e-16 0.6 54,000 36,000 Plot 8 1 0 5.37e-12 0.4 53,000 30,000 Plot
Speed =FAST, Filter = g.
1024x1024 central regions in each CCD were observed at a range of exposure times. No overscans are available, so the images were bias-subtracted, making their zero level uncertain by +-2adu.5s exposures were combined to make a flat field to correct pixel-pixel varations. The flat field from each CCD was then independently re-normalised (so that flattened adu values in each CCD would reflect their raw normalisation).
Image statistics were obtained in the window (in IRAF format) [420:597,415:560] in each CCD. Exposure times for each CCD were made shorter by -22.0ms to account for the shutter timing error measured from the same data.
Plots were then made of counts vs exposure time to derive linearity corrections.
25DEC00 - Polynomial Linearity Corrections for WFI. CCD A0 A1 A2 A3 Residuals
(%)Max ADU
above biasUncorrected Non-linearity
< 0.5% below
(adu above bias)1 1 0 3.23e-12 0.2 56,000 36,000 Plot 2 1 0 2.06e-12 0.2 53,000 40,000 Plot 3 1 0 5.97e-12 0.2 41,000 28,000 Plot 4 1.01254 -1.53256e-6 1.53935e-11 0.2 52,000 <10,000 Plot 5 1 0 3.97e-12 0.3 44,000 32,000 Plot 6 1 0 7.29e-12 0.3 56,000 26,000 Plot 7 1 0 -8.00277e-11 2.77197e-16 0.2 53,000 40,000 Plot 8 1 0 6.17e-12 0.3 54,000 28,000 Plot
Useful Links and other PFU/WFI Resources
- AAO Wide Field Imager (WFI) and Prime Focus Upgrade (PFU) page.
- WFI and PFU Commissioning and Performance Status.
- RSAA WFI Page
- RSAA WFI Workshop Page (workshop was held Oct 14-15 1999)
- WFI Survey Page including draft proposal resulting from the "Science with the WFI" Workshop.
- RSAA WFI Project page (Project team access only)
- IRIS2 Page
This page maintained by Chris Tinney (cgt@aaoepp.aao.gov.au)