Reading stacked scan using IUE RDAF procedures

We start IDL and load the RDAF procedures as usual. The stacked data consists of primary array header, a binary table extension header, and 1 row of 6 columns of binary table data, so we read in a header, an extension header, and the 6 columns of the extension.

Let us say we are interested in the OI 988Å multiplet towards the star Lambda Sco. Using the U1 archive search we find there is a stack of scans of this line stored in the file c001-074.bu1. Now that we have the data the first thing we do is use the command ifitsrd to read in the data file:

IUE_IDL>ifitsrd,"c001-074.bu1",1,h,eh,wave,flux,back,nstack,sigma,scans
 
Reading binary table row:       1
Column   1:   field = WAVELENGTH data type = E  npoints = 68
Column   2:   field = NET FLUX data type = E  npoints = 68
Column   3:   field = BACKGROUND data type = E  npoints = 68
Column   4:   field = NSTACK   data type = I  npoints = 68
Column   5:   field = SIGMA    data type = E  npoints = 68
Column   6:   field = SCANS    data type = I  npoints = 4

We can now plot Net Flux (Counts/14 seconds) vs. Wavelength (in Å):

	IUE_IDL>plot,wave,flux

Then we can overplot on this the sigma:

	IUE_IDL>oplot,p1,p5

The result is the following plot:

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Example provided by jtl