iraf.net

I have two sets of two files which I combine to create two individual files. I have been using SCOMBINE task for this. It has worked for most expect this. I do not understand why the task is changing the dimensions. Here is what the imeader command gives for these four files:
LP860apr10-9.fits[1000,11][real]: LP860-41
LP860apr9-10.fits[1000,11][real]: LP860-41ntel_stand12-13.fits[1000,11][real]: HD141442
ntel_stand13-12.fits[1000,11][real]: HD141442Now I combine the first two. I get the following: 20070430LP860.fits[1003,11][real]: LP860-41This is what is expected. However when I combine the other two files, I get: 20070430-tell.fits[1002,11][real]: HD141442I am not sure why I have "1002,11" here? Below is my lpar for SCOMBINE. The @comb2 simply contains the names of the two files I am combining. Any ideas? [code:1:732ea06414]
input = "@comb2" List of input spectra
output = "20070430-tell.fits" List of output spectra
(noutput = "") List of output number combined spectra
(logfile = "STDOUT") Log file\n
(apertures = "") Apertures to combine
(group = "apertures") Grouping option
(combine = "average") Type of combine operation
(reject = "none") Type of rejection\n
(first = no) Use first spectrum for dispersion?
(w1 = INDEF) Starting wavelength of output spectra
(w2 = INDEF) Ending wavelength of output spectra
(dw = INDEF) Wavelength increment of output spectra
(nw = INDEF) Length of output spectra
(log = no) Logarithmic increments?\n
(scale = "none") Image scaling
(zero = "none") Image zero point offset
(weight = "none") Image weights
(sample = "") Wavelength sample regions for statistics\n
(lthreshold = INDEF) Lower threshold
(hthreshold = INDEF) Upper threshold
(nlow = 1) minmax: Number of low pixels to reject
(nhigh = 1) minmax: Number of high pixels to reject
(nkeep = 1) Minimum to keep (pos) or maximum to reject (neg)
(mclip = yes) Use median in sigma clipping algorithms?
(lsigma = 3.) Lower sigma clipping factor
(hsigma = 3.) Upper sigma clipping factor
(rdnoise = "0.") ccdclip: CCD readout noise (electrons)
(gain = "1.") ccdclip: CCD gain (electrons/DN)
(snoise = "0.") ccdclip: Sensitivity noise (fraction)
(sigscale = 0.1) Tolerance for sigma clipping scaling corrections
(pclip = -0.5) pclip: Percentile clipping parameter
(grow = 0) Radius (pixels) for 1D neighbor rejection
(blank = 0.) Value if there are no pixels
(mode = "ql")
[/code:1:732ea06414]

Without seeing the images, my only guess is that there's a difference in starting wavelengths that's causing the different sizes. Since you didn't specify the wavelength parameters, the task computes them based on the existing dispersion in the images.