Polar Alignment

I have an SCT with a wedge on a tripod all north of the equator. With the tripod set in the ground and the wedge set to (more or less) the correct latitude I can swing the scope east or west with no issues. Got that part. Every "polar alignment" guide I have ever seen tells you to point the scope at Polaris. Got that part.

What if I want to look at something in the southern sky? The south celestial pole is (technically) below the horizon. What I have been doing is leaving everything alone and pointing the scope south rather than north, and it appears to work more or less right. Would a drift alignment to the south work the same as to the north?

From experimentation the answer seems to be easy, but given the complete lack of a polar alignment guide for people looking to the south I began to wonder.

Polaris is behind a tree, by the way. Doing a north polar alignment would require a chain saw.

Thanks!

A polar alignment requires you to move your polar axis (the one with the right ascension hours) so that it is parallel to the true pole of the earth. This does not mean north or south pole, but the actual pole that represents the axis on which the earth spins.

Your clock drive in your telescope will then move the scope to the west so that it can follow the stars.

Your clock drive can move one way if you are aligned to the north pole, and the other way if you are aligned to the south pole, so you can align to either pole, as long as you tell the motor which one you are lined up on.

If you are north of the equator, I believe you have to align on the north pole (you don't have to be able to see Polaris to do this, however) and tell your motor you are so aligned. (If you bought your telescope north of the equator, and it has never been south, it is almost assuredly already thinking it is north.)

So, you want to align to the north pole. You can use a compass (corrected for the magnetic anomaly for your location) to point the forks north, and the latitude adjustment to make sure the forks are at the proper latitude. What matters is the forks.....not the tube.

If this is not an accurate enough polar alignment for your uses, then you can do a drift alighment, or an iterative two star alignment. If you are north of the equator, you use directions for those north of the equator, and your forks will point roughtly to the north star (even if you cannot see it).

And this should answer your question about looking south. The only thing that matters is that in fact your mount's axis (which is the central axis of the forks) is aligned to the pole. The tube can point wherever you want it to, including to the south. In this way, a "north polar alignment" allows you to see all the way to your southern horizon.

Alex


Alex