This page (revision-3) was last changed on 07-Dec-2016 14:14 by PeterYoung

This page was created on 05-Jul-2007 17:18 by PeterYoung

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Version Date Modified Size Author Changes ... Change note
3 07-Dec-2016 14:14 2 KB PeterYoung to previous
2 09-Oct-2008 16:44 1 KB PeterYoung to previous | to last
1 05-Jul-2007 17:18 931 bytes PeterYoung to last

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At line 1 added 4 lines
[{ALLOW edit EISMainUsers}]
[{ALLOW view Anonymous}]
!!Spatial offsets between the two CCDs in the X direction
At line 15 added 13 lines
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!Update
In order to reduce the X-offset between the detectors, tests were performed to see if moving the slit position would improve the situation. The EIS slit assembly has a "paddle-wheel" design (note: not to be confused with a "windmill" design), with four paddles that contain the slits. Normally the paddle-wheel is rotated through 90 degrees to bring the different slits into the beam. The paddle wheel can also be moved by small amounts (a fraction of a degree) and this is what the tests did.
After inspecting various data-sets, an optimum position for the slit assembly was found and a permanent change was made on __24 August 2008__. Preliminary checks on the data suggest that the spatial offset between the two CCDs is now around 0.5 arcsec - see the image below.
[Image|CCDOffsetX/JS_CH_140x256p.jpg]
Shown are images in Fe XIII 202.04 and Fe XIV 274.20, and a cut through the data is indicated by the dashed lines on the images. The bottom plot shows the cross sections for both lines, and cross-correlation gives a displacement of less than 1 pixel (0.45,0.39) as indicated in the legend.
If you have made any measurements of the offset since 24 August 2008 and find a different value, please report it here.
This page (revision-3) was last changed on 07-Dec-2016 14:14 by PeterYoungTop