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NarrowWorksheet2
NarrowWorksheet2

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At line 3 changed one line
In general the user should calibrate EIS data before he/she attempts to look it. This is because EIS data are affected by warm pixels on the CCD which make it difficult to study the images.
In general the user should calibrate EIS data before he/she attempts to look it. This is because EIS data are affected by warm pixels on the CCD which make it difficult to study the images. The EIS calibration routine is called 'eis_prep'.
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IDL> filename=
IDL> filename=’eis_l0_20061209_113031.fits’
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To calibrate your data, the standard call to eis_prep is
then the standard call to eis_prep is:
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IDL> eis_prep,filename,/default,/save,/retain,/quiet
IDL> eis_prep, filename, /default, /save, /retain, /quiet
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The /save keyword results in two files being created in the user's directory
The /save keyword results in two files being created in the user's directory which have the names:
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eis_l1_20061209_113031.fits\\
eis_er_20061209_113031.fits
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NOTE: “bad” data (referred to as missing) are flagged with a value of -100 in the error FITS file arrays (not the level-1 arrays). The missing data in the level-1 arrays are replaced with the median value of the surrounding pixels. This is useful for display purposes, but for scientific analysis you should not use any pixels flagged as missing.
With the /default option, eis_prep does the following things:
The first file is the level-1 EIS FITS file containing calibrated intensity arrays. The second file is the error file which contains the corresponding 1-sigma intensity errors for the arrays stored in the level-1 file.
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* Flag any saturated data as missing (saturated data have a DN value of 16383)
* Remove the CCD pedestal and dark current
* Flag hot pixels as missing
* Flag warm pixels as missing (not implemented at present)
* Flag cosmic rays as missing
* Calibrate data, and create error arrays
Full details of the various keyword inputs to eis_prep are given in EIS Note #1, where detailed descriptions of the various steps performed by eis_prep are given.
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!Exercise
#Using commands from Worksheet 2, how many pixels in the Fe XII 195 data array have been flagged as missing by eis_prep?
One featue of eis_prep is that bad pixels in the data are flagged as 'missing'. These bad pixels can be due to cosmic ray hits, saturated pixels, dust particles on the detector, hot pixels and warm pixels. The latter are by far the most numerous, and described in more detail in EIS Note #6. Bad pixels are flagged only in the error file and are assigned a value of -100. The bad pixels in the level-1 file are replaced by a value interpolated from neighbouring pixels. More details about the effect of missing data on EIS data analysis and interpolation methods are given in EIS Note #6.
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This page (revision-13) was last changed on 07-Dec-2016 14:14 by Peter YoungTop