Here’s my experience. I used to be a pro photographer and am pretty snobby about glass.
If your dad’s primary motivation is to film stuff with his phone, then
the key component is the phone/scope interface. I found that you’ll wind up using the scope with the phone attached 100% of the time, as it’s not simple to really snap it on/off without messing up the alignment on the subject. Plus, it’s great looking at a comparatively huge image with both eyes off the phone vs one eye off the eyepiece.
While I don’t own this (yet), this unit gets rave reviews at $170. A single gripper of the same thing daves you $20. It’s worth the extra $20 imho.
Buy Novagrade Universal Double Gripper Digiscoping Adapter for Smartphones featuring For Mobile Devices up to 4.3" Wide, Dual Grippers for Improved Stability, Works with 39-60.75mm Eyepieces, Anodized Aluminum Construction, Polymer Compression Ring Set. Review Novagrade null
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My experience: prairie dog shooting with my fairly nice Razor 27-60 85mm vs my brothers complete POS Walmart special. In bright daylight with a phone,
it didn’t matter. Irritating!
Can’t remember the phone adapter my bro used. It was a pain in the ass!
So, if I were your dad, I’d buy that adapter and spend the rest on the scope. I think I know the type of guy your dad is, and the video is what he wants.
The only fly in the ointment is low light use. When does your dad typically see the deer? Guessing the regular hours, like dusk/dawn, but maybe he’s trained them to be 9-5’rs lol.
So buy a sub-$330 scope and see how it works in lower light with a phone (just hold up the phone to test, the phone might see better than your eye can, depending). Maybe use a TP tube, cut to just the right length and fitted over the eyepiece, for a better test. Return scope if it sucks.
I saw a 100% video spotter somewhere, no phone needed, but then there’s the prob of getting that video onto his phone.
edit: I forgot about the needed $20 scope eyepiece adapter. That scope is gettin’ cheaper!