This page (revision-9) was last changed on 27-Mar-2020 14:38 by Peter Young

This page was created on 24-Feb-2010 18:22 by PeterYoung

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NarrowWorksheet3
NarrowWorksheet3

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[{ALLOW edit EISMainUsers}]
[{ALLOW view Anonymous}]
!!!Worksheet 3 - Reading and browsing data
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!!!Worksheet 2 - Reading and browsing data
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Following on from Worksheet 2, you can now read the EIS FITS file from the command line:
The EIS FITS file to be used in all the worksheets is from 9-Dec-2007, 11:30 UT:
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{{{
IDL> data=obj_new(‘eis_data’,filename)
}}}
filename=’eis_l0_20061209_113031.fits’
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data is an IDL object. Information is extracted from the object through a large number of ''methods'' and some examples are given below.
(NOTE: you may need to add the path name, depending on where the file is located.)
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To determine the coordinates of the center of the raster, do:
To read an EIS FITS file from the command line, type:
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{{{
IDL> xcen=data->getxcen(/raster)
IDL> ycen=data->getycen(/raster)
}}}
IDL> data=obj_new(‘eis_data’,filename)
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To find the exposure time for each exposure of the raster, do:
data is an IDL object. You can extract information from the object using various methods. E.g.,
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{{{
IDL> exp=data->getexp()
}}}
IDL> exp=data->getexp()\\
IDL> xpos=data->getxpos()\\
IDL> wd0=data->getvar(0)\\
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A single data window can be extracted by doing:
wd0 is a 3D array containing the window data for the specified window (0 in this case). You can get a list of all methods by doing:
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{{{
IDL> wd=data->getvar(195.12)
}}}
IDL> data->display_methods
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where the specified wavelength is used to pick out the data window containing that particular wavelength. The first dimension of WD is always wavelength, the second is always solar-Y, and the third can be either solar-X or time depending if the observation was a raster or a sit-and-stare observation.
To extract the header into a string array, do:
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A complete list of methods is obtained by doing
IDL> hdr_obj=data->gethdr()\\
IDL> text=hdr_obj->getbte_hdr()
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{{{
IDL> data->display_methods
}}}
A number of useful header tags can be sent to a structure by doing:
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while more [detailed information on some methods|EISmethods] is given elsewhere on the EIS wiki.
IDL> eis_get_hdr_struc,data,hdrstr
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To find which wavelength windows are contained in data, do:
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!Exercises
IDL> wininfo=eis_get_wininfo(filename,/list)
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For these exercises you will need to refer to the [EIS object methods page|EISmethods].
!Exercise
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#Create and plot an IDL map for the Fe XII 195.12 line by taking the moments of the line.
#Now use the getvar() method to extract the 195.12 wavelength window. Sum the 3D window over the wavelength direction (use the IDL total() routine), and plot the resulting image. How does it compare to the map image plotted above? See the object methods page for why it is different.
#Using the following commands, can you work out the direction that EIS rasters? (east-west, or west-east)
#Using eis_get_wininfo and the getvar() object method, extract an image in Fe XII 195 by summing all wavelength pixels in the window. Plot the image. What do you have to do to the image to orient it correctly? (You may need to refer to XRT images from Day 1 of the workshop.)
#Using the following commands:
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{{{
IDL> ti=data->getti_1()
IDL> sec=data->sec_from_obs_start(ti)
IDL> xpos=data->getxpos()
}}}
IDL> aux_data=data->getaux_data()\\
IDL> exptimes=data->sec_from_obs_start(*(aux_data.ti_1))\\
IDL> xpos=data->getxpos()\\
work out in which direction EIS rasters (east-west, or west-east).
This page (revision-9) was last changed on 27-Mar-2020 14:38 by Peter YoungTop