Angular Diameter Calc shares a small python program HOWLARG.py, which calculates how we see distanced objects by angular diameter. It calculates actual size or distance by setting angular diameter.
HOWLARGE.py shows the Angular Diameter of the Moon looking from the Earth on startup prompt.
Angular diameter of Moon
Size:3,478.80km(r=1,739.40km)
Distance:a=384,400.00km
Angular diameter:0°31'6.63''
1 pinkey width or narrower
Below this prompt, HOWLARGE.py asks you which parameter you want to set for calculating angular-diameter, size or distance.
[0]Quit [1]Size [2]Distance
[3]Diameter; keep target size
[4]Diameter; keep distance
[5]Unit
If you want to calculate the angular diameter of the Earth from moon, you only set [1]Size to the Earth's one.
Enter Number [0]-[5] > 1
Enter radius of target >> 12742
Size:12,742.00km(r=6,371.00km)
Distance:a=384,400.00km
Angular diameter:1°53'57.53''
pinkey - thumb witdh
Angular diamater 1°53' is same with the width of your thumb on streaching arms. You can describe as following.
The Earth looks bigger than I expected. It was the same size of my thumb.
If you want to know the distance of airplane from angular diameter, aka looks, set the [3]Diameter keep target size. Try following.
Set the unit to m(meter).
Enter Number [0]-[5] > 5
Enter Unit >> m
Size:12,742.00m(r=6,371.00m)
Distance:a=384,400.00m
Angular diameter:1°53'57.53''
pinkey - thumb witdh
Set the target size to 63: Length of Boeing 777.
Enter Number [0]-[5] > 1
Enter radius of target >> 63
Size:63.00m(r=31.50m)
Distance:a=384,400.00m
Angular diameter:0°0'33.81''
1 pinkey width or narrower
Set the [3]Distance keep target size, with comma separated degrees. 20,0,0 means 20°0'0.00’’. This angular diameter means the object looks same with your span from the top of thumb to pinkie of your hand on outstretched arm.
Enter Number [0]-[5] > 3
Enter Delta in D,M,S >> 20,0,0
Size:63.00m(r=31.50m)
Distance:a=181.40m
Angular diameter:20°0'0.00''
index-pin ~ thumb-pin span
You get the 181m and can describe it.
Boeing flew over me looked as the palm span. Could I sneak stealthily to reach there? Is could be 150m, or longer?