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generating images of same size - Printable Version

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generating images of same size - Jan Kohnert - 02-22-2007 17:34

Hello all again,

I just wanted to automize our color-imageing generation an fell over stiff, as I'm quite unhappy with the work ds9 does.

So I downloaded and tested stiff on a frameset (I have R and z, the green channel is just an average of the both channels, but I get colors in ds9 Wink ).

The error message I get is:
ankoh@avalon /work3/jankoh/VLT_P73/reduc_col $ stiff -c /work2/jankoh/stiff.conf ext072-R_SPECIAL-1963-set_3.fits ext072-green.fits ext072-z_GUNN-1963-set_3.fits
----- Inputs:
ext072-R_SPECIAL-1963-set_3.fits: "ext072" 1836x2052 32 bits (floats)
Background level: 0 Min level: -0.161941 Max level: 32.2262
ext072-green.fits: "ext072" 1937x2296 32 bits (floats)
Background level: 0.0088954 Min level: -0.0599343 Max level: 13.706
ext072-z_GUNN-1963-set_3.fits: "ext072" 1828x2186 32 bits (floats)
Background level: 0 Min level: -0.1331 Max level: 26.4869
----- Output:
stiff.tif: 1836x2052 24 bits gamma factor = x1.00

> *Error*: Image width doesn't match in ext072-green.fits

jankoh@avalon /work3/jankoh/VLT_P73/reduc_col $

By reading the manual, I learned that the image size (in the pixel number sense) must be the same for all images, and the manual refers to swarp to align the images.

So after all, I'm stuck: I do not find any useful infrmation in the swarp docs. My data are processed by SCAMP and SWARP (in deed, the green image also is computed by swarp), but how do I get the images to the same pixel size? Is that possible with swarp or am I misinterpreting the manual (in that case I would use MIDAS for that purpose)?

Best regards Jan

RE: generating images of same size - Henry Joy McCracken - 02-23-2007 11:21

well, after processing in (with scamp and swarp) the first image in your set,
you should copy the header of that image into a .head file corresponding to the names of your other images (ie., coadd_b.head or coadd_r.head or whatever). You will see in swarp a message 'reading in external fits header' when you generate your coadd_b.fits and the new image will have the same size and pixel scale as the other images. So then you can you use stiff (or sextractor in dual image mode for that matter).


RE: generating images of same size - Jan Kohnert - 02-23-2007 12:20

Thanks a lot, that does exactly the trick.

I never used header-files for output images, so I wasn't aware of that possibility.

Best regards Jan