Astronomy 350: Unix Lab III: Data Reduction with SCC data• Note in what follows dont type the <> brackets.• Login to the moxie lab and from there login to the machne 129.3.1.55 usingssh -X -l < username > 129.3.1.55.• Now o pen up some ”xterms” using the command xterm& from your com-mand line.• Now you can go on to take a look at the images we got at SCC.• If you had already started this from last time, delete those files using theunix command rm. If you are in the SCC directory, type rm -r * to deletethe files.• They are in the directory shashi/SCC, sorted by date. Copy them overand take a look. Use a command like cp -r ∼/shashi/SCC . The dot at theend in the above command is important. What does the -r do (use man cpor look it up on the web)?• The files all have a *.F IT extension. the IRAF program likes to have fileswith a .fits extension. We are going to use the command mv to do this.Find out a bit about mv.• Look up on google using a search term like ”renaming multiple files in unix”.Go to the link with the Debian administration url and read it.– Type echo $SHELL. What does it say?– Type bash and t hen type echo $SHELL aga in: what does it say?– Go into the 9-10-08 directory. Do an ls, you should see many files withthe *.FIT extension.– Type: for i in *.FIT; do echo $i; done– Describe what happens and describe what this command does. Whatdoes the $ i refer t o it this?– This is an example of a shell script and is very commong in moreadvanced Unix computing.– Now type, and be very careful about typing this correctly:for i in *.FIT; do mv ”$i” ”${i/.FIT}”.fits; doneand describe what has happened and the shell script above.– Your *.FIT files should now be *.fits files.– Type exit to exit the bash shell.1• Now you are ready to do a very simple data r eduction exercise. We aregoing to use the data from the first night, make a master bias and subtractthis from all the images, then make a master dark a nd subtract this fromall t he science images.– cd into the directory that contains the data for the 9-10-08.– Type mkiraf and answer the following question with xterm.– Now start up a ds9 in the background with ds9&. Click ok if needed.– Type ls *.BIAS.* What happens?– Type ls *.BIAS.* > biasfiles and look at the file biasfiles. What hashappened?– Take a look at some of these biasfiles using display in ds9. Use imstatto get some statistical details about the bias files. Note these down.Can you find a quick way to do imstat on all the Bias files?– Now start up IRAF using cl.– The command imcombine can be used to combine a bunch o f fits filesinto a master. Tyep epar imcombine.– For the input file, type biasfiles.– For the o utput file type mbias.fits.– The combine para meter should say average.– Now type ”shift, colon, go”. Display the fits file mbias.fits. Whathas happened? Use imstat t o compare mbias.fits and the orig inal biasfiles. Note down the stats details.– Now exit IRAF by typing logout.– Now create another file, called imagefiles, which contains the files*NOAUTODARK* and *.DARK.fits: that is the science images withno autodark subtraction and the dark fits files. Make a copy of thisfile with cp called imagefilesa.– Use vi or another editor to edit the file imagefilesa such that insteadof being *.fits its *a.fits.– Now begin IRAF with cl again.– Use epar imarith to subtract the master bias files f r om all other files.For the input list in epar imarith put imagefiles, the operand is - , thesecond operand is mbias.fits, the outfile is imagefilesa. After you runit, what has happened? Use imstat to make sure some things havechang ed and note down some of the statistics.– So now you have subtracted the master bias from all the images. Lo-gout of IRAF.2– Now create a master dark from the existing dark images, that is t hoseimages with *.DARK.fits.– Create a file of images from o utside IRAF: use ls *.DARK.fits > dark-files.– In IRAF use imcombine to create a master dark using similar methodsto what you used above to make the master bias.– Put t he master dark in a file called mdark.fits and use imstat to com-pare its statistical properties with the original darks. Note these down.– Now outside of IRAF, create a file containing a list of all the scienceimages and use the above methods to subract the master dark fromall these science images - but use the method above to make sure thatthe originals are not overwitten.– Compare the statistical properties of the final, reduced science imageswith the original raw images. Note these down. There should be some,though not a great deal of difference.– Try to save some of the fits images as pdfs or jpgs from the ds9 programand append these to your output.– Repeat for the other 2 nights of observations.– In imcombine you used the average as a means of combining the darksand biases. Investigate if there are any differences if you use a