So, Stormwrack has rules for "base spotting distance", where you can make a DC 20 Spot check to spot something at a given distance (based off of a table). If you're within half that distance, you can see it automatically.
Underdark has a similar rules for spotting light sources - you can spot light sources at a range equal to 20 times their radius of illumination if you're in complete darkness, or 10 times the radius if you're in low-light conditions.
Let's make a triplet of "reasonable" extensions:
1) If you're within 5 times the radius of a light source, you can spot it in bright light conditions.
2) We use the row for flying observers for anything that wouldn't be impeded by the rotation of the planet.
3) You can use the "hills or peaks" column for anything really big. Yes, this produces weird results.
So, let's look at our tools:
1) Normal spotting gives us a penalty of -1 on our Spot checks for every 10ft away we are.
2) Let's say that a spyglass doubles all distances involved (-1 for every 20 ft, and the base spotting distance is twice as far).
3) We're going to assume someone untrained in Spot who takes 20 on their roll for everything.
OK, so particularly large sunspots can be spotted from Earth without a telescope. Let's call that a DC 22 (because Joe Genero probably won't notice unless you point it out to him). Now, checking the proper row on the table, that tells that the Sun must be 100 miles and 20ft away. By extension, all of the other planets we can see have to be about that far away.
How about the moon? Well, we can see features on it automatically, so it has to be within 50 miles of Earth.
=---=
So, yep, if you can cast Teleport, you can go to the moon - I mean, it isn't that far away!
