The most obvious factor is the azimuth, represented by the compass bearing. Azimuth is defined as "the angular distance from the north along the horizon to the point where a vertical circle through a celestial object intersects the horizon." Yikes!!! Or to put it into plain English, it's a measure of how far round the horizon the satellite is from due north.

All geostationary satellite systems are placed over the equator and orbit the earth at such a speed as to match the planet's own rotational speed. That way they stay over the same point of the earth's surface. There are many such systems serving different parts of the world and obviously they can't all be in the same place. Astra 2 is situated at longitude 28.2º east of due south, (over eastern Congo), hence the reference to 28.2E.

The value of 28.2º equates to a compass bearing of 151.8º (180 - 28.2). However, in practice there are very few places where that's the precise bearing. As you move around Europe, the satellite (if you could see it!) would appear to move around, just as a tall building would appear to move to the left as you walk to the right. So the exact compass bearing from you to the satellite will depend on where you are at the time. You'll find a table of compass bearings from various towns and cities across Europe here.

Now consider the effect of having a satellite beaming its signal from a position somewhat to the east of due south. The frequencies are polarised alternatively horizontal and vertical to avoid cross-interference between adjacent frequencies. If the satellite were located directly south of you, the signals would indeed be either vertical or horizontal but because it's actually some way round the curvature of the earth, it appears tilted as seen from Europe. To compensate for that tilt and to keep the dish's LNB correctly aligned to the signal polarisation, the LNB has itself to be turned by an equivalent amount. That degree of tilt is what is referred to as skew. However, just to complicate matters a little, the Astra 2 system isn't aligned correctly relative to the earth's axis! It's out by 7º which means that the values calculated by some websites will be wrong. Those listed on my page are correct!

Somewhere on the LNB housing (the position varies depending on the make of the dish) there is a clamping screw and by loosening it the LNB can be rotated within its mount if the skew needs adjusting.

The final component is of course the elevation which is perhaps the hardest to measure. It's simple enough to explain - it's the angle of elevation of the satellite above the horizon - but pointing the dish to that angle is more tricky. Most dishes are of the offset focus type where the signal strikes the face of the dish at an angle and is then reflected downwards to the LNB. Because of that, the dish has to point somewhere below the true angle of elevation. (In many parts of the UK, the dish will appear to point directly at the horizon.) There is usually a scale marked on the mounting behind the dish, though it's only a very rough approximation.