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  • Mohammad Akhlaghi's avatar
    Correct estimation of MUSE PSFs and deconvolution · 2c31a594
    Mohammad Akhlaghi authored
    The model MUSE PSFs were incorrectly calculated until now! I was
    mistakenly assuming that the `FSF01FWA' was the FWHM. However, the
    FWHM must be calculated from `b*lambda+a' where `b' is the value to
    `FSF01FWB' keyword and `a' is the value of `FSF01FWA'. The effective
    `lambda' (or wavelength) to use for each broad-band filter is the
    throughput-weighted average wavelength of the filter.
    
    So, the pipeline now uses the HST filter throughputs to find `lambda'
    and then uses the values of these keywords to generate the proper FWHM
    for the Moffat function. The throughputs will be downloaded if not
    already available. The FWHMs decreased from around 14 pixels to around
    10 pixels.
    
    After implementing this correction, a test run of the deconvolution
    gave a better result. The reason was that the image crop to feed into
    the deconvolution algorithm was larger and so lower frequencies could
    be sampled. After seeing this trend, I increased the truncation radius
    of the model MUSE PSFs and also the deconvolution image size and saw
    that the deconvolution output kernel is becoming better and better. I
    finally stopped at 6 times the FWHM since it was apparently not making
    much more change.
    
    So, now the proper kernel to convolve with the HST images is created
    and we can directly compare the results with the MUSE images without
    worrying about a larger PSF. After convolution, the HST images are now
    also sampled to the same pixel size as MUSE.
    2c31a594