colouring

colouring makes a colour image from frames taken through standard filters, typically Johnson B, V and R.

It transforms the frames into a colour space such as CIE 1931 XYZ, so the result approximates natural colours. The output is a 3-D FITS cube with one plane per band.

Usage

munipack colouring [options] files

List the frames from short to long wavelength (B, V, R).

All bands must be on the same pixel grid. Resample them with kombine first, using the same --rcen, --dcen, --width, --height, --scale, --angle and --reflex for each band.

For correct colours the bands need a white balance. Calibrated frames, or ctph values given with -q, give absolute intensities. Otherwise give weights (-w), a white spot or a white star; without any of them colouring warns that the colours are not balanced.

Options

Lists are comma-separated, with one item per input file (use semicolons if your locale uses a decimal comma).

Option	Argument	Default	Description
-c, --cspace-input	name	guessed from FILTER	Input colour space, e.g. 'Johnson BVR'.
--cspace-output	name	'CIE 1931 XYZ'	Output colour space.
--list	—	—	List the available colour-space transformations and exit.
--ctable	file	installed ctable.dat	Colour-transformation definitions.
--phsystab	file	installed photosystems.fits	Photometric systems table.
-w, --weights	w1,w2,…	—	Weights of the bands.
-q, --ctphs	ctph1,ctph2,…	from calibrated frames	ctph of each band, for calibrated output.
-b, --backs	b1,b2,…	estimated	Background level of each band.
--disable-back	—	off	Do not estimate or subtract backgrounds.
--white-spot	x,y [pix]	—	Centre of a region that should come out white.
--white-star	x,y [pix]	—	Centre of a star taken as white (B − V = 0).
--white-radius	real [pix]	7	Radius of the white spot or star.
-o, --output	file	colour.fits	Output file (overwritten if it exists).
-B, --bitpix	-32, 32, 16, 8	-32	Data type of the output.
--verbose	—	off	Print the guessed colour space and progress.
-h, --help	—	—	Show the help and exit.

Output

One 3-D FITS cube with one plane per band.

Examples

Turn B, V, R frames on a common grid into a colour image:

munipack colouring -o m27.fits m27_B.fits m27_V.fits m27_R.fits

Balance uncalibrated frames on a white star at pixel (512, 488):

munipack colouring --white-star 512,488 --white-radius 5 -o m27.fits \
    m27_B.fits m27_V.fits m27_R.fits

See which colour-space transformations are available:

munipack colouring --list

Notes

• The input colour space is guessed only for three frames with FILTER exactly B, V, R (or X, Y, Z); other sets need -c.