Last modified: December 2022

AHELP for CIAO 4.15


Context: Tools::Gratings


Correct the time-dependent tilt of LETG/HRC-S spectra by adjusting TG_D.


detilt infile outfile tilt


detilt reads in an LETG/HRC-S evt2 file (usually this will be the output of the dewiggle tool) and adjusts the TG_D values of all events by applying a linear correction as a function of TG_MLAM. The tilt is in units of deg/Ang and can be estimated from Fig. 5 ("Time dependent tilts in deg/Å") at Cross-Dispersion Wiggles. Only TG_D values are affected; the output file will not exhibit any changes if displayed in sky or detector coordinates.

detilt is generally used in combination with the dewiggle and symmetrize commands--also contributed software tools--to prepare LETG/HRC-S spectra so that narrower spectral extraction regions can be used to improve the S/N of low-S/N data.


detilt input_evt2.fits output_evt2.fits -1e-7

Adjust TG_D -= TG_MLAM * -1e-7


name type ftype def min max reqd stacks
infile file         yes no
outfile file output       yes no
tilt real   0     yes no
verbose integer   0 0 5    
clobber boolean   no        

Detailed Parameter Descriptions

Parameter=infile (file required stacks=no)

Input FITS file event list with columns TG_D and TG_MLAM.

Parameter=outfile (file required filetype=output default= stacks=no)

Output FITS file event list with modified TG_D column.

Parameter=tilt (real required default=0 stacks=no)

The residual dispersion angle, in units of deg/Ang.

Parameter=verbose (integer default=0 min=0 max=5)

Tool chatter level

Controls the amount of information tool prints to the screen.

Parameter=clobber (boolean default=no)

Remove outfile if it already exists?

About Contributed Software

This tool is not an official part of the CIAO release but is made available as "contributed" software via the CIAO scripts page. Please see this page for installation instructions.


There are no known bugs for this tool.

See Also

simple_hist, simple_stats
combine_grating_spectra, detilt, dewiggle, dmtype2split, mktgresp, symmetrize, tg_bkg, tg_choose_method, tg_create_mask, tg_findzo, tg_resolve_events, tgdetect, tgdetect2, tgextract, tgextract2, tgidselectsrc, tgmask2reg, tgmatchsrc, tgsplit