Centroid of star image

Question

I'm trying to calculate the centroid of a star image:

I'm fitting a 2D gaussian with least squares in order to get the centroid of the star with sub-pixel accuracy. And, in fact, I get a float number for the coordinates X and Y of the centroid using http://photutils.readthedocs.io/en/stable/api/photutils.centroid_2dg.html?highlight=centroid_2dg

Now I want to test this algorithm with different position of the real centroid and compare them with the calculated centroid, but I don't know how to "move" the centroid within sub-pixel accuracy. I only know hot to move it in a pixel order.

Can anyone help me?

Answer 1

Though you can perform subpixel translation by interpolation (bilinear or bicubic), I would suggest a better approach.

Take a higher resolution image (IMO synthetic is good enough), smooth it to remove high frequencies (and lower the Nyquist frequency), and subsample. This will allow you to apply small displacements (by whole pixels at high resolution) and obtain the corresponding low-resolution images.