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I was working until late last night & only had ten minutes before Sirius set behind the hills on the other side of the valley.

That maximised the atmospheric turbulence in the sky above Heidelberg, but left me little time to experiment. It's very tricky lining up the iPhone camera with the exit pupil of the binoculars & then holding it steady.

I did manage to get some 30fps footage through the 3 x tele lens, but couldn't line it up at 120 or 240fps, as of course it gets fainter at high speed.

FWIW, I think that when filming at 30fps, the iPhone 15 uses the best wide-field camera for both 1 x & 3 x zoom, but when you switch to slow motion (i.e. 120fps or 240fps), it uses the separate wide-field & tele cameras.

Which means you have to align everything again, handheld.

Which is very awkward.

And the 3 x tele camera is a lot crappier than the wide-field one, so I'm not sure how well it'll work at high speed – there probably won't be much light, even through my binoculars.

Being able to film in slow motion really does help – it gives a much better impression of how the refractive index changes "boil".

That said, it's not intuitive what's actually going on here.

The light coming from Sirius is along a very narrow "beam", as it's a point source. Changes in the refractive index along that beam break the blue-white spectrum into its constituent colours, moving some out of the beam, while others remain in it – that's what creates the changing colour scheme.

But the defocussing only happens in the binoculars, making the point source into a disk. Then you see colours swirling & drifting across the disk, but how that relates back to what that actually represents spatially is non-obvious.

Is it a "map" of the turbulence / refractive index changes across the 70mm entrance pupil of my binoculars, extended in a tube through the atmsophere & out into space? Or is it all immediately local to my set-up?

Perhaps an optics / telescope expert will chime in

And obviously this would be a lovely thing for someone with a much better set-up to reproduce, with a defocussed telescope pointed at Sirius & a much better high-speed video camera, with more optical magnification, low noise, & running without (excessive) compression.

Indeed, I'm sure someone has – worth a search.

@drs1969 Interesting – I figured that such a thing must exist, but never really bothered to search for one. Aligning the iPhone entrance aperture with the binocular exit pupil is a real faff, so this could definitely help.