Yes. currently, IDL does not have any capability to read and write excel files. This is a serious weakness. I do not know if or not the software developers are aware of this.   

You can write to an ascii file fairly easily using the printf procedure.  For Excel documents, go to the code contribution library on this site, there are two excel reading utilities that may help.  To write to Excel, I would write to a .csv file, which Excel can read. To do a .csv (an ascii file with comma delimiters) you can do something like this: pro make_csv     x = randomu(seed, 10,100, /double)     openw, lun, 'test.csv', /get_lun, width=10000         sizex = size(x, /dimensions)     stringx = strtrim(x,2)     stringx[0:sizex[0]-2, *] = stringx[0:sizex[0]-2, *] + ','         printf, lun, stringx     close, lun, /file     free_lun, lun end

Well, if you are using Windows and you have IDL 6.3+ and a copy of Excel on your computer, you can in fact read/write excel files using ActiveX/COM controls.  Search the code contribution site for Excel and you should find some code to help you do that.  Last time i looked they had a nice little read_excel routine packaged up for you, but if you look a little further into the code they give you, you can find routines for writing excel files and for calling the activex routines to do it all yourself.   But as for your output, it sounds like you have some issues with your output file loop.  are you opening/closing the same output file for each image? if so, make sure you're opening the output file for appending, not writing, or you're only gonna see output for the last image.  If that's not the problem, something else is wrong with your loop somewhere.   Jeff