I was experimenting by taking photos of the moon using an 1000mm MTO-11ca lens and thought I should get even closer by adding a teleconverter (Kenko Pro 300 3x). The picture quality is not sharp at all but by using a realy high ISO (25000) and fast shutterspeed 1/2500 I was able to get rid of the worst blur (I was shooting on a tripod but I think atmospheric effects was moving the moon in and out of focus).
As could be expected the images where VERY noisy Links bellow. I usually only go up to ISO 1600 reluctantly (Canon 5D Mark II).
How much can be salvaged with images this noisy? I was trying both Digikam and RawTherapee but did not find any denoising algorithm that made any difference at all. I would have expected the denoising to at least smear out the picture and kill the noise even if it failed to recover the details.
What is the best that can be done in these cases?
Edit: Some more experiments have revealed that the ”athmospheric effect” might in reality be caused by my lens not being in temperature equlibrium as per this article https://fotosaurier.de/?p=2029