CDS tutorial  -  2004.02.04, kamio@kwasan.kyoto-u.ac.jp

0. CDS/SOHO Instrument

Slits: 2x240, 4x240, 90x240arcsec
NIS-1 range: 308-381A
NIS-2 range: 513-633A
GIS (2x2,4x4arcsec)
For detailed information, refer to:
Harrison, R.A. et al. 1995, Sol. Phys. 162, 233. 

1. Quick look

; make sure 'cds' is included in SSW_INSTR
a=readcdsfits('s27073r00.fits')
cds_new_spike,a  ; remove cosmic ray
vds_calib,a ; calibration (photon-events/pixel/s)
dsp_menu,a ; GUI menu

2. Get a sample spectrum for fitting

sp = gt_spectrum(a, window=0, xix=0, yix=0, lambda=lam)
; get the spectrum at (0, 0) in window #0
plot,lam,sp,psym=10

3. Obtain initial value for fitting

xcfit,lam,sp,fit ; GUI menu
print_cfit,fit
eval_cfit,lam,yy,fit
oplot,lam,yy,linestyle=1

4. Fit a block of data

da=gt_windata(a, 0) ; retrieve data of window #0
; da: 3D array in the format of [wavelength, x, y]
wts = 1. / (da > 1) ; weights
cfit_block,lam,da,wts,fit,-100,result,residual,/double

For spectral line identification, refer to:
Brooks, D.H. et al. 1999, A&A, 347, 277. 

5. Display results

setflag,missing=-100
; for 1 component of gaussian
plot_image,reform(result[0,*,*]),title='Intensity'
plot_image,reform(result[1,*,*]),title='Position'
plot_image,reform(result[2,*,*]),title='Width'
; backgroud and residual
plot_image,reform(result[3,*,*]),title='Background'
plot_image,reform(result[4,*,*]),title='Chi^2'

6. CHIANTI Database

; make sure 'chianti' is included in SSW_INSTR environment
chianti_ne
; example: Si X  log(Te) = 6.15
; density - intensity ratio of Si X 347.409 / 356.030

chianti_te
; example: Mg VII  log(Te) =5.80
; Te - intensity ratio of Mg VII 319.019 / 367.672

For lines suitable for density and temperature analysis, refer to:
Harrison, R.A. et al. 1995, Sol. Phys. 162, 233.