BTX 85v95v115? Observation and digiscoping

[Ztm91]

I have been trying to research the best option between 85mm,95mm, and 115mm objectives for a Swaro BTX. I will primarily using the setup for observations as I will be entering grad school for wildlife management and am looking to do some work with mountain goats. Additionally, I would like to get an adapter to use my Mirrorless camera to capture some video potentially.

I’ve read many people say that overall they prefer the 85 with the BTX as it’s the best mix of cost, weight and performance with the FOV and resolution being better than the 95. While many reviewers have said it’s challenging to tell the difference between any of the objective sizes with a BTX eyepiece and there’s just a small difference in fading light.

It seems most recommend either the 85 or the 115. I’ve seen some reviews here where the 115 and Kowa 99 have noticeably better resolution than the 95.

I feel like naturally the 115 would be the best option for sitting behind for long periods of observations and digiscoping, but would it be significantly better than the 95 or 85 to justify the much higher cost and weight for my usage?

 

[SomeJackassOnAForum]

You can't mount a mirrorless to a BTX.

Everything else is size/ weight vs performance. Bigger is better for digiscoping if stable, but that means a Bigger, heavier tripod and head.

 

[Ztm91]

Thank you for the clarification there. I was under the impression that TLS APO adapter connected to the objective lens but after watching a video I see what you referenced with it connecting to the eyepiece instead. Weight isn’t a big concern at the moment if the performance is proportional, as I’m used to hauling around a 500mm lens and camera combo and monopod to shoot goats that weighs quite a bit more than the btx. I thought with the adapter I might be able to also bring along the camera and switch out the eyepiece for the camera but now that I know it requires a second eyepiece that would not be an ideal setup for the digiscoping format, at least with the mirrorless anyway. I suppose the digiscoping isn’t the top priority. I guess for me personally it probably comes down to performance vs price and if the 115 is really worth the extra money vs an 85 or 95.