I tried out another night sortie yesterday. ISO capped at 25600 for 645Z with 90mm f/2.8 and shutter speeds between 1/125 and 1/180, hoping that the at least 2 stop SR of the lens would give me decent images.
I repeated the same for K1 with 77mm, ISO capped at 12800 and shutter speeds between 1/60 to 1/250.
Most shots were from some distance between the chopper and the subject. So, the relative motion was slow.
I am yet to evaluate the images, but prima facie, I do not see much improvement.
So, you are right. Quite possibly, the overall light intensity of the city is not adequate and even if one uses gyro stabilisers like the Kenyon ones, as long as you are moving, with some relative motion between you in the chopper and the subject being photographed, you are unlikely to get decent images. However, if you hover in one place, then a highly stabilised set up including external gyro stabilisers might give decent images, if you bring down the shutter speeds to low ones like 1/30 to 1/60 at ISOs ranging from 25600 to 6400.
The only other option for images with aerial perspective is to climb on high rise buildings and take pictures of the world below
I will continue with the daytime aerial photography, which is comparatively reasonably simple for me.
I have only gone through the images using Adobe Bridge and Photoshop.
I will try out the DxO and Topaz software.