Impact of Atmospheric Conditions on Spotting Scopes (1 Viewer)

An interesting story of a New Zealand telescope maker, possibly Graham Loftus, was told to me.

A New Zealand professional observatory had a large telescope installed, maybe 24 inch or larger and charged the public for viewing.

Possibly Graham Loftus did not think that the public should be charged for viewing the heavens.
So in a couple of days he made a slightly larger mirror and diagonal. He used possibly 3 oil drums welded together to make the tube.
In a few days the completed telescope was put in a nearby car park and free viewing was given.
The amateur telescope was better than the professional one as the optics were made for cooling temperatures rather than for a fixed temperature.

The professional observatory did not like this free viewing and competition, but couldn't prevent it and decided in their wisdom to give free viewing to the public.

Graham Loftus made about 20 telescopes from 20 inch to 36 inch aperture.
In general they were corrected for cooling temperatures.
I think he was a friend of the maker and rider of the 'World's fastest Indian' Burt Munro.

For some reason my server does not allow me to read the shooter reference.

But in my head.
7mm holes at 1000 yds or 914m?
7mm at 914,000 mm.
1 part in 130,500.
206,000 divided by 130,000 is about 1.6 arc seconds.

I could see black sunspots with a penumbral diameter of 38 arc seconds with unaided eyes with 20/15 vision or 34 arcseconds with my head braced against a lamp post.
Persons with excellent vision see 20 arsceconds sunspots with unaided eyes and an optimal safe filter. Penumbral sunspots need to be slightly larger than black transits such as Mercury or Venus.
This assumes absolutely optimum brightness of the Sun using safe filters.

In other words black spots on a white background are visible at smaller sizes than people assume.
But this assumes a black spot on a white background.
If there is not enough contrast a bullet hole cannot be seen even close up.
At 1000 yards one would need very good transparency and Seeing conditions.

I think that with excellent conditions only 30x would reveal 7mm bullet holes at 1000 yds for 20/15 vision.
But observing near ground level, I doubt that really excellent views are normally possible.

My friend who saw the masts on the Isle of Wight, maybe using his 65mm Acuter spotting scope.
I think his observing height was 230ft. He said that the sea horizon was very sharp and clear. This would be 19 miles away in normal conditions.
So at 45 miles to the masts, He would see objects at 400 feet above sea level or higher on the Isle of Wight.