Well from planetary diameters, (assuming 1" to 2,000km to give Earth a 6 1/2" template):
Lifeless Rock/Moons up to 3" template
Pluto: 2274 km
Triton: 2700 km
The Moon: 3476 km
Io: 3630 km
Mercury: 4,880 km
Titan: 5150 km <- Perhaps this should be an "Earthlike World"
Ganymede: 5262 km <- Perhaps this should be an "Earthlike World"
Earth Like Worlds 4" to 9" template
Mars: 6,794 km <- Perhaps this should be a "Lifeless Rock"
Venus: 12,103.6 km
Earth: 12,756.3 km
Gas/Ice Giants 10" or larger template
Neptune: 49,532 km
Uranus: 51,118 km
Saturn: 120,536 km
Jupiter: 142,984 km
So;
if 1 inch is about 2,000 km, Neptune would need a 25" template,
if 1 inch is about 3,000 km, Pluto would need a 1" template, Earth a 4" template and Neptune about a 16" template,
if 1 inch is about 4,000 km, Earth and Venus would need 3" templates and Neptune would need a 12 1/2" template. Pluto would need a 1/2" template.
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On the show, when G'Sten leads the Narn raid against a Centauri World (The Long, Twilight Struggle?) The Narn's are seen firing from very large distances, probably well beyond any visual range.