Bug in the units of the shift in Zernikes 1/2 calculation

[tobias-liaudat]

We have a small issue with the units inside the function in the code snippet below, the function takes arctan() of a quantity with units [1/m], which is dimensionally incorrect:

wf-psf/src/wf_psf/utils/preprocessing.py

Lines 39 to 44 in 7c4b515

	return (
	zernike_norm_factor
	* (tel_diameter / 2)
	* np.sin(np.arctan((dxy / reference_pix_sampling) / tel_focal_length))
	* 3.0
	)

See the issue #175

There is a unit problem inside the arctan! The reference pixel shift should be unitless and the 1e-6 should be to change from [m] to [um]!

Given the small angle approximation there is almost no error with the current implementation, but has a conceptual error.

TODO:

• Fix the unit mismatch on the function
• Write corresponding unit test for this

[jeipollack]

this is a duplicate of #175, but we can just make this a sub-issue of it.