Interesting topic. About 5 years ago, we had joined the local bird club, and on outings I would be photographing, while all the other members were scoping. My wife was stuck with a pair of binoculars. So, as I had also been very interested in digiscoping, I did a very hard target search about how good the photos using a scope could be. Lots and lots of talk, zero actual photos to examine. So we pulled the trigger and bought a Swarovski 95 mm, and a tripod, our first. As well as the 30mm Nikon D850 adaptor. We got the angled model to help offset the weight of the camera.
Tried it out at the house, found out that as soon as I attached the D850, the scope would not hold its posit on the tripod. Not to worry, Swarovski had the solution. A rail attachment that pushed the scope further out on the tripod to offset the weight of the camera. So, long story short, shooting a bird, no matter whether it’s a plover or a GBH, the image did not hold a candle to the photos I was used to with the D850. Granted, had I shot with the D850 at that distance it would not be any good either.
So I experimented with birds at a closer distance, and those were quite good through the scope, but really no better than the D850 with a 500m PF.
The D850 is history, now a Z9 with the 600mm PF. My experience is that it is quite impossible to get the photos you want from a great distance. Just not possible. Photos for ID, no problem, but photos for the wall, never going to happen.
In case anyone is interested, I still have the 30mm Nikon adaptor for the Swaovski.
Good luck
CM