  A simple least-squares optimisation enables the determination of the spectrum
for irregularly sampled data that is readily reconstructed using an adjoint
transformation of the Non-Uniform Fast Fourier Transform (NFFT). This is an
improvement upon previously reported iterative methods for such problems, and
is competitive in terms of time complexity with more recently proposed direct
NFFT inversions when considering comparable matrix pre-computation steps. The
software is highly portable, and available as a convenient Python package using
standard libraries. Given its mathematical simplicity however, it can be easily
implemented on any platform.
