Worksheet 2 - Reading and browsing data#

The EIS FITS file to be used in all the worksheets is from 9-Dec-2007, 11:30 UT:

filename=’eis_l0_20061209_113031.fits’

(NOTE: you may need to add the path name, depending on where the file is located.)

To read an EIS FITS file from the command line, type:

IDL> data=obj_new(‘eis_data’,filename)

data is an IDL object. You can extract information from the object using various methods. E.g.,

IDL> exp=data->getexp()
IDL> xpos=data->getxpos()
IDL> wd0=data->getvar(0)

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:

IDL> data->display_methods

To extract the header into a string array, do:

IDL> hdr_obj=data->gethdr()
IDL> text=hdr_obj->getbte_hdr()

A number of useful header tags can be sent to a structure by doing:

IDL> eis_get_hdr_struc,data,hdrstr

To find which wavelength windows are contained in data, do:

IDL> wininfo=eis_get_wininfo(filename,/list)

Exercise#

1. 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.)
2. Using the following commands:

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).