| -Lew Thomas 4-28-01 |
First, we shall apply Dawes Limit which strictly applies to the resolution of two equally bright points of light. This is
R” = 4.56/D (1)
where
D = the diameter of the telescope objective in inches
R”= the resolving power in seconds of arc.
The mean distance of the Sun from Earth is 149,000,000 km. Therefore, the linear dimension of any object on its surface is
R = rq (2)
where
r = the distance to the Sun = 149,000,500 km
q = the angle of the Sun object subtended at the Earth observer in radians
R = the linear dimension of the Sun object in km
Combining (1) and (2), we have
R = r 4.56p/(3600×180 D)
R = 3294.18/D (3)
Using this relationship and assuming a perfect telescope, the following table is constructed
| OBJECTIVE DIAMETER | MINIMUM DISCERNABLE SUNSPOT |
| INCHES | KILOMETERS |
| Unaided eye (0.1 in.) | 30,390 |
| 4 | 824 |
| 6 | 549 |
| 8 | 412 |
| 10 | 329 |
| 20 | 165 |
| 100 | 33 |
| 200 | 17 |