Just wondering if anyone knows is it the coordinate for a point that is the arcane connection to that place?
If it is what's to stop a mage from simply using intellego imaginem to observer the array of stars at 0,0 since the coordinate for the point is known even if the exact location is not?
It is not.
In the 5th edition book, page 84, there is a list of various items and their effectiveness as arcane connections. They all imply that you need a tangible part of something in order to have a connection. Simply knowing the location, even down to the detail of a coordinate, isn't a connection.
Besides, such accurate coordinates don't exist yet.
If you happen to understand astronomy, (Intellego is not required) and you look up at the stars, you might know where you are on the planet, what time of year it is, etc, but that doesn't give you a connection to anything.
BellaDonna I was referring to something in Ancient Magic.
Oh dear. 
Havent got that far. haha sorry 'bout that!
Yes, it is an AC to the point.
The point is mystical, though, located you-know-where (if you read the book) so you cannot simply "guess it" triangulating 3 other points. At least this is the reasoning I used to prevent my players from saying "hey, if we know 3 coordinates (they do, since they have a corrupted copy of ptolemys work) we use a little bit of known maths of the time and voilá, insta-origin point!". I will have them move their asses down there if they want the trick.... or will introduce it via an other Evil SG plot 
Cheers,
Xavi
No you misunderstand the question. If you can use the coordinates to target any place you know the coordinates of and you need to know the array of stars at the origin (0,0) to calculate your own coordinates then what is to stop a character from simply transporting themselves to 0,0 which is a known coordinate. Or, even easier is using intellego imaginem to observe the array of stars from that point.
The point is, knowledge of the coordinates for the origin is inherent in the system, its 0,0. You need information on the array of stars at that point to measure the distance of other unknown points and come up with the coordinates there, but the coordinates of the origin are KNOWN. So why bother with going to the hesperides at all?
The point in the hesperides is only along the zero latitude, its not actually the origin point itself.
Isn't the point that 0,0 is not a known point until you actually get there, and after you take the readings then everything becomes a known point.
If you already had unlocked the coordinate system then, yes, you could use intellego imagonem range AC spells to unlock the coordinate system but the whole point is that you haven't yet.
Until you take the readings you can't use the system.
Plus the coordinate system has been corrupted to a certain extent so that attempts to extrapolate the origin point fail mysteriously.
No according to the text the corrupted copies of the geography contain some useful coordinates designed to entice mages to seek to unlock the system. You don't need to work out the system to actually use the coordinates as arcane connections. What you need the system for is to be able to use the formula in the geography to calculate the coordinates of other points on your own.
Technically you could pick a coordinate at random and send something or someone there, the danger is you don't know if you are targeting over water or land. The whole reason it is assumed they would seek out the hesperides is because it is the only land on the zero latitude, it is not actually the origin point 0,0.
However, I think the ability to observe at a distance was just a severe oversight since seeking the three points needed to calculate the position of the stars at 0,0 can be avoided with a intellego imaginem spell.
This is why I posted my comment on trigonomnetry not working for some mystical reasons (you know which ones if you read the chapter). 
There is more here than plain old maths to calculate where 0,0 is located.
Cheers,
Xavi
There are some things you are missing here:
- If you don't do the initiation, you don't get the power. This is how magic works in Mythic Europe. You need to pay to be a magus, and its not a matter of if you can make it easier. Cleverness is less important than suffering the correct experiences. As the book says "Attempts to dervie a system wqith a more convenient origin point mysterious fail." West is West.
*When you say "No according to the text the corrupted copies of the geography contain some useful coordinates designed to entice mages to seek to unlock the system." you are saying "The co-ordinates which are designed as bait should be enough for me to avoid the trap that the bait is set on.". Not so. The bait is -bait-. You can't use them to infer a way past the trap for which they are bait. The system of workings you'd use to try and do that has been deliberately corrupted, as you point out, so that you can't simply extrapolate from the known co-ordinates. For example, Ptolemy's stada are wrong.
Remember, the co-ordinates are a shorthand for a stellar array, they are more than just two numbers.
- You need to know the stellar correspondences of (0,0) to just put random numbers in the system and see where you end up. Until you have 0,0, you can't just go to any two numbers you decide to go to (speculative co-ordinates). Unless you have been given the numbers by someone who has the power to use them, they are not arcane connections.
You can only use the co-ordinates to target any place you know the numbers if you have:
calibrated the system by deriving (0,0) or
got the numbers from someone else who has already done the above. and that section of Ptolemy's work is not found in the copy of Geogpraphica players have.
So the question of "Why can't I just go to 0,0" is answered pretty easily. You don't have the power to go to just choose a number like 0,0 (or 1,1, or 180,180) until either you gain the power to do so (which, co-incidentally, you gain by going to 0,0) or by getting the info from someone who has it already.
Or, even easier is using intellego imaginem to observe the array of
stars from that point.
It's not an Arcane Connection until either you gain the ability to derive co-ordinates yourself, or you are given working co-oridnates by someone else. So, what's your Arcane Connection, here? And its Vim, not Imaginem, and the spell to do it is
Also, it's Vim, not Imaginem. You are looking at more than light.
And the origin is arguably a wall of fire as tall as the sky.
And there's the Guy Who Set This Up, who will kill you before you get the chance to destroy his carefully laid plans. He knows lots of dragons, who love him like a father and do whatever he asks, yeah? 8)
Or, perhaps you are wrong about this. I note from your description that you have missed the spell on page 91 which, if you boost it to Arcane Connection, will do exactly this, -if- you have the Arcane Connection.