Well, to be honest, GoPro Hero is not a best option for a scope cam.
There are three strong reasons to support that:
1 - there is no zoom
2 - you can't adjust the focus
3 - 1.5" display (if there even is one) is too small for any serious hunting/pest control because it's hard to see anything precisely
But, there are also three big pluses for GoPro Hero:
1 - it records audio @ 240 FPS
2 - it records 240 FPS at 720p resolution
3 - it records @ 240 FPS indefinitely
Still, one has to deal with three problems first to get a useable scope cam
1 - I have found that a cheap 2x telephoto lens with an adapter is good enough to get a decent size picture into the frame
2 - Well you can't beat that one, but, GoPro has a fixed focus from about 12" to infinity so with a 2x telephoto lens it should have most scope's reticules in more or less sharp focus
3 - I don't really take this one too much into account since airgun hunting/pest control is forbidden by law in my country but, the screen provided is good enough for most plinking sessions and, you can always use a FPV setup and view the picture on a bigger screen you usually use for FPV (if you are into FPV using quad/hexa/octa copters or other RC flying machines). Note that you can't use a GoPro app on your smart phone or on your laptop/tablet because there is no live stream when using 240 FPS
I did have Casio Exilim ZR1000 but videos were worse in quality (high speed engine that Casio uses haven't changed in more than a decade!) and there is no audio @ 240 FPS. 480 or 1000 FPS are useless options because video quality is so low.
Sony RX100 MK4 records at much higher resolutions at much higher FPS but it can only record for 2-3 seconds which is just too short for my use and it costs 2x as a GoPro
In this day and age, if you don't have any of the three cameras mentioned above, my best bet would be iPhone 6 or Samsung S7 because both can record @240 FPS with audio, have adjustable focus and zoom and have 5" - 6" displays. Choosing between those two, my money would probably go to Samsung
Here is one of the videos I've made with my GoPro Hero4:
more can be found on my YouTube channel.
There are three strong reasons to support that:
1 - there is no zoom
2 - you can't adjust the focus
3 - 1.5" display (if there even is one) is too small for any serious hunting/pest control because it's hard to see anything precisely
But, there are also three big pluses for GoPro Hero:
1 - it records audio @ 240 FPS
2 - it records 240 FPS at 720p resolution
3 - it records @ 240 FPS indefinitely
Still, one has to deal with three problems first to get a useable scope cam
1 - I have found that a cheap 2x telephoto lens with an adapter is good enough to get a decent size picture into the frame
2 - Well you can't beat that one, but, GoPro has a fixed focus from about 12" to infinity so with a 2x telephoto lens it should have most scope's reticules in more or less sharp focus
3 - I don't really take this one too much into account since airgun hunting/pest control is forbidden by law in my country but, the screen provided is good enough for most plinking sessions and, you can always use a FPV setup and view the picture on a bigger screen you usually use for FPV (if you are into FPV using quad/hexa/octa copters or other RC flying machines). Note that you can't use a GoPro app on your smart phone or on your laptop/tablet because there is no live stream when using 240 FPS
I did have Casio Exilim ZR1000 but videos were worse in quality (high speed engine that Casio uses haven't changed in more than a decade!) and there is no audio @ 240 FPS. 480 or 1000 FPS are useless options because video quality is so low.
Sony RX100 MK4 records at much higher resolutions at much higher FPS but it can only record for 2-3 seconds which is just too short for my use and it costs 2x as a GoPro
In this day and age, if you don't have any of the three cameras mentioned above, my best bet would be iPhone 6 or Samsung S7 because both can record @240 FPS with audio, have adjustable focus and zoom and have 5" - 6" displays. Choosing between those two, my money would probably go to Samsung
Here is one of the videos I've made with my GoPro Hero4:
more can be found on my YouTube channel.