In this document:
The fSAO display tool can be used to display the raw spectro images. This can only display the raw images, without overscan-correction. This means that there will be a baseline value of between 500 and 1250 ADU on each of the amplifiers. You will clearly see the split in overscan values between the left and right amplifiers.
From within SOP (or IOP), type the following (substituting for $MJD and $filename as appropriate):
sop> cd /data/spectro/$MJD sop> set img [ regReadAsFits [regNew] $filename ] sop> saoDisplay $img
sop> saoDisplay $img "-min 1000 -max 1300"
I've set up IDL on sdsshost.apo (and on sos.apo, plate-mapper.apo), for use in displaying spectro images. Note that since all the spectro data is automatically copied to sos.apo (by the Son-of-Spectro cron job), you can display images on either machine.
First, set up IDL and the idlspec2d product, and start up IDL:
% setup idlspec2d % idl
Move into the directory for MJD 51886 and display the first image:
IDL> cd,'/data/spectro/51886' IDL> img=rdss_fits('sdR-b1-00007538.fit') IDL> atv,img
There is another tool built on top of ATV that will overplot the bad column mask in red:
IDL> atvrawspec,'sdR-b1-00007538.fit' IDL> atvrawspec,'sdR-b1-00007538.fit',min=0, max=20 ; <-- Force display range
To read in a raw image and median-filter before displaying,
IDL> img=rdss_fits('sdR-b1-00007538.fit') ; <-- Read a raw image IDL> sdssproc,'sdR-b1-00007538.fit',img ; <-- Or read + overscan-correct IDL> atvmedian(img,9)
Another useful command is
IDL> logsheet
The SOS-extracted spectra can be displayed using IDL tools on the computer sos.apo. For the full documentation, see http://spectro.princeton.edu/idlspec2d_doc.html#APOPLOT.
You must be logged onto sos.apo (or whichever machine is running Son-of-Spectro). Set up the idlspec2d product and start IDL with:
setup idlspec2d idl
IDL> apoplot, 401, 100
IDL> apoplot, 401, 100, nmed=9
IDL> apoplot, 401, /magsort, /netimage
IDL> apoplot, 401, 100, mjd=52282
IDL> apoplot, 401
Quitting IDL:
IDL> exit
There's another useful (but slow!) command for analyzing bias and dark frames. This is the APO_PLOTBIAS procedure. It takes as its only argument a spectroscopic exposure number, then plots a histogram of bias values for all 4 cameras of that exposure:
IDL> apo_plotbias, 7538
IDL> apo_plotbias, 7538, plotfile='bias.ps'
After making its plot, the APO_PLOTBIAS procedure prints out a select number of percentiles. The 2-percentile is the value at which only 2% of the pixels are below, the 50-percentile is the value at which 50% of the pixels are below (e.g., the median), etc.
I find the typical percentiles for a bias to be:
Filename 02% 05% 10% 50% 90% 95% 98% ---------------- ---- ---- ----- ---- ---- ----- ---- sdR-any-exposure -8 -5 -3 1 7 9 11