Hi Steve and all,
First of all, I'm sorry for not being active on the forum lately. I've been ill for the last two weeks. Nothing serious; just a bronchitis but I can't remember ever being so ill. Now I'm starting to feel better, so I'm afraid you won't get rid of me so easily
I've made a brief tutorial to describe some easy steps with this image. The first one is to find a good estimate of the PSF with the DynamicPSF tool:
Note that I have sampled about 50 stars (less would suffice) around the object of interest. Since the image shows varying star shapes throughout the field, I have sampled the region close to the main subject for deconvolution.
The PSF model image has been generated by selecting all PSF measurements and clicking the export synthetic PSF
button. This is definitely the best way to generate a robust PSF model with the DynamicPSF tool. I strongly discourage using average PSF parameters for this purpose.
The next step is deconvolution. I have used nearly default parameters with the Deconvolution tool. 20 iterations of the regularized Richardson-Lucy algorithm, with default regularization parameters and no mask. The only slightly critical parameter has been the global deringing threshold. This is the before image shown with custom screen stretch parameters (for better inspection of the galaxy core):
and this is the image after deconvolution:
Note that I have used no mask in this case. Wavelet regularization and global deringing have been sufficient to prevent the worst side effects of deconvolution for low-SNR areas (noise intensification) and small-scale bright features (ringing around stars and other bright structures).
The third step is a nonlinear stretch with HistogramTransformation. I have applied automatic STF histogram parameters.
Next, I have applied HDRMultiscaleTransform with 5 wavelet layers:
A side effect of the HDR multicale transform algorithms is that bright structures that are close to saturation in the original image can cause artifacts. This can be seen as 'concave' bright star cores in the screenshot above. To fix this problem we need a simple star mask:
This mask is very easy to build because we only need protection for the brightest stars. This is the mask active and shown for the image:
and here is the result of HDRMultiscaleTransform applied with the star mask enabled:
Finally, some noise reduction may definitely help this image. Let's keep it classical with the good old ACDNR tool. Before:
and after ACDNR:
Hope this helps.