Specview Cookbook for Combining Low dispersion Spectra

1. Specview Cookbook for Combining Low dispersion Spectra M. Smith, I. Kamp, and I. Busko Space Telescope Science Institute

2. In this tutorial we will combine five IUE and HST spectra as follows: Scale fluxes, trim spectrum ends as needed Coadd spectra and plot the coaddition (temporarily) detrend the spectrum FFT-filter the spectrum Coplot the FFT and coadded spectra Review relevant windows Save data files

3. First, get into Specview: Click on “empty applet” link at: http://specview. stsci.edu/applet (spectrum plotting window)

4. Approve two security certificates (first time only)” Click on “always,” then “yes,” for the two certificates offered.

5. To read in data files Click on “File,” “Read from File” tabs and … …highlight, open files, one at a time.

6. Once files are loaded in… …and open Processing Window. …open tab: Coplot/process tab (arrow) processing window

7. Next activate the window’s contents: Highlight all spectra of interest (left-mouse + shift) Click on “Process”

8. Up comes the Processing Window for these five spectra… …and at the same time…

9. …the two panel plot: (For now ignore upper panel) Plotting window shows the 5 coplotted spectra.

10. To modify scale factors click to open cell and enter new factor, click cell shut. (guess values: trial & error!) Enter scale Factors and click “Execute.”

11. Rescaled Continue changing scale factors as necessary and click “Execute” to plot.

12. Two-panel plot shows before/after effects of inter alia scaling of the spectra.

13. Now work through red/blue wavelength limits in the same way. When done click “Execute”.

14. Upper: rescaled & spliced Inspect the resulting dual panel plots. Lower: raw data coplotted, no action

15. Click Resample tab: Let’s go to single panel, click on “Execute this Step”… Accept default (finest grid sampling) or input your own value. and “Execute.”

16. The coplotted, scaled & trimmed spectra:

17. Proceed to Coadd step: (last chance to exclude spectra!) Click on “Execute this Step” + Execute.

18. Our trimmed, coadded spectrum:

19. Digression-1: At this point you may wish to save your coadded spectrum. (Click on File/”Save as” tab over plotting window)

20. Digression-2: Click on “File/Save As” in spectrum window. Enter saved coadded spectrum file name.

21. Now proceed to Detrend step: Click on “Execute this Step” + Execute.

22. (Detrend step is transient: used internally for next (filter) step.) Type in wavelength near left end of spectrum. Click in cell (now pink) and enter value. Click cell shut.

23. Work on flux of left end: Enter flux through which you want the working spectrum to be detrended and again click shut.

24. Completed Detrend window Make sure “Auto Compute” is clicked off and Click “Execute.”

25. The temporarily detrended spectrum: To FFT filter, click “Filter” in processing box.

26. FFT filter processing: Click “Execute this Step” and “Execute.”

27. Need to change the FFT filter?: UNCLICK “AUTO CUTOFF”! Enter a new cutoff frequency in box, Click “Execute.”

28. The resulting Brault-White FFT filter…

29. …and the FFT’d spectrum: Save this spectrum as for slide #18 before if you wish.

30. Save the filtered spectrum as before if you wish.

31. If necessary, read in coadded spectrum:

32. To coplot coadded & FFT spectra,” click “Coplot,” highlight processed spectra, and click “Plot.”

33. Final coplot of the spectra: Coadded Filtered

34. We are now done. Note we can save the result spectrum as an ascii file. The plots cannot be saved except as screen shots.