In reply to Bottom Clinger:
Other thoughts... seems crazy carrying two big optics around. If you're keeping the DSLR anyway, have you tried just taking the scope and using your phone to 'digiscope'? I've been surprised by how good the results can be, and I haven't even got a proper mount.
>Also, when I see very long range photos taken with this Sony camera, they can be better than a dslr equivalent.
Can you expand on 'better' there?
I haven't used the RX10iv but I've used used the RX10 and RX10ii extensively shooting guidebooks etc. The sensor is ok, it can be surprisingly good with the right handling but will never blow you away. My concerns with the iii and iv are size/ weight (not that small) plus modest AF and noise above base ISO.
Other option is Nikon P600 or similar - tiny, cheap, 1440mm equiv. Cons - tiny noisy sensor, no RAW, weak AF but for social media its often quite sufficient.
Ultimately I'd think about why you're carrying a camera. For record shots, to help with ID, for social media or for print/ display? A DSLR is always going to best the others for quality and AF, but do you 'need' it?
Post edited at 10:58