Aligning the masks

The first script we need to run in order to make a spectral map is align-mask, which uses the comparison lines to calculate the large-scale offsets and adjust the dewoff file accordingly. To edit the parameters for align-mask, we use the editpar routine:

editpar align-mask

type q to end

SEARCHBOX               10       half width of search range
MAGFACTOR              100       magnification factor for offset vectors
LAMFILE         somelines.dat       line list file
NAVER                    1       number of neighboring points to average
THRESHOLD         0.100000       minimum flux ratio spot to background
SIGLIMIT         10.000000       line rejection threshold
MAXFLUX         65000.000000       maximum flux
WINDOWSIZE        7.000000       width of PGPLOT window in inches


Change parameter:

For these data, I put the lines at 4921.93, 5015.68, and 5400.56 Angstroms in somelines.dat, because those lines are relatively isolated and not saturated. Avoid using more than 3 lines, as this may cause confusion in align-mask. Then, we run the command:

align-mask -o CSIfld5 -f ift0012
parameter file ./align-mask.par found
Processing "CSIfld5.SMF".
** Unknown keyword "DREF" ignored.
** Unknown keyword "DATE" ignored.
** Unknown keyword "XFWH9HRN1EPQX4OR4HP4KGD_QYMVUM
FXKNVSS7QHPASN9ETBCADLCWZA_W5NU23IMLDY6Z" ignored.
Using E2V1 distortion corrections
Delta=(-10.01 5.48) Sigma=(3.35 5.08)
Clipping out (1532.45,-343.53)
Clipping out (1534.07,-546.96)
Delta=(-10.02 5.48) Sigma=(3.33 5.06)
Clipping out (-2270.69,1252.93)
Clipping out (425.03,2647.53)
Clipping out (425.70,2435.20)
Delta=(-10.03 5.48) Sigma=(3.31 5.06)
Clipping out (-2518.94,3031.25)
Clipping out (-1780.39,-1325.13)
Clipping out (-3346.16,-229.54)
Clipping out (-3346.76,-485.34)
Clipping out (2674.58,-582.58)
Clipping out (1204.60,-1409.91)


297 matches found. sigma=  12.74 pixels  Continue? y

Average scale =          0.99869    Reset scale? y

Average rotation angle =  -0.013    Reset angle? y

Average X,Y Offsets =    -9.9    6.2 pixels. Apply shifts? y
Creating new dewar offset file ift0012.dewoff

A PGPLOT window will pop up with a vector plot of the calculated offsets. As you can see in Figure 3, align-mask detects the large-scale shifts and applies these corrections to the dewoff file. If you do not see a large-scale shift such as this for other data, then most likely you need to either increase your SEARCHBOX or adjust the dewoff file manually using the adjust-offset routine. Since we see a noticeable bulk shift, however, we can proceed to adjust the scale and angle, and apply the shifts to the dewoff file.

The output of align-mask in this case is ift0012.dewoff. Edit CSIfld5.obsdef to use ift0012.dewoff and then rerun align-mask. After a few iterations, you'll notice that the offset "sigma" has gone down to less than 2 pixels (see Figure 4), which means we now have a good enough dewoff to move on.

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Next: Constructing the Spectral Map Up: Running Sample IMACS data Previous: Spot-check the features   Contents

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Edward Villanueva 2014-08-27