Dear list;

`I am honestly not certain whether this, or the SciPy list, is the`

`appropriate place to post this; please let me know if I got it wrong.`

`I am convolving a 1D data set containing a relatively narrow peak, with`

`a relatively narrow Gaussian kernel, in order to emulate the effect of`

`atmospheric seeing on astrophysical observations.`

`I have a 1D data array 45 pixels long, and a Gaussian kernel, and run`

`np.convolve(data, kernel, mode='same') on the two arrays, the resulting`

`array's peak is shifted relative to the origin. I have attached a plot`

`to illustrate.`

`The original data is shown in blue. When I convolve it with a symmetric`

`kernel (black), I get an offset resulting peak (magenta). If I flip the`

`kernel -- even though it is perfectly symmetric -- the resulting curve`

`is offset in the opposite direction (yellow). However, if I offset the`

`kernel so it is centered exactly one pixel below the central value, the`

`output array gets centered correct (red), even if I flip the (now no`

`longer symmetric) kernel.`

`This is using Numpy 1.11.3, python 2.7.13, on Anaconda 4.3.0 64-bit on`

`Ubuntu 16.10`

`Using astropy.convolution, reproduces the correct red curve, so I can`

`use that for now, but it seems to me this is either a bug or, if it is`

`indeed the intended behavior, a word of caution would be merited in the`

`docstring.`

Cheers, Emil Rivera-Thorsen

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