NOTE!: This also is a good image to use to re-emphasize what was said earlier about what is meant by 'Up/Down', 'North/South'  as relates to the view in the telescope.  

Since the scope tube rotates around it's Polar axis as it moves from the East to the West, the 'Up', or 'North' part of the telescope is that part which is directly AWAY FROM the Polar axis of the scope (toward the 'top' of the scope) , and the 'Down', or 'South' refer to that part of the tube which points directly TOWARD the Polar axis of the scope (toward the wedge)! Therefore, a 'drift' of a star that seems to 'drift' down', will apparently drift TOWARD the Polar Axis. Don't confuse these directions as referring to the 'up/down' of this page!

The beginnings of seeing some 'drift' in the star is becoming apparent, but in reality we'd be a bit more refined that this. When we wish to check and adjust our telescope for being out of alignment in an East/West direction, we would actually select a star that is within 10 degrees or so in Declination from the Celestial Equator and perhaps within 20 or so minutes in Right Ascension of our meridian.  That's where this particular error will be most apparent, especially when we use a high powered eyepiece and the error is only slight.

This is a more realistic view of the section of sky that you'd be watching, to check for Polar mis-alignment in an East/West direction.  As you can see, as the scope follows the star in Right Ascension, the star slowly 'drifts' toward the Southern Celestial Pole... or 'Down' in our eyepiece, regardless on whether we're somewhat on the East or West side of the meridian.  

This gives us rule number one for drift alignment: If a star near the meridian drifts SOUTH (down) in the eyepiece of the telescope, the SOUTHERN direction on our telescope axis is too far WEST of the SOUTH Celestial Pole, and the NORTHERN direction on our telescope axis is too far EAST of the NORTH Celestial Pole!

Here we have the same section of the sky selected, and we're watching the same star, but in this case the Southern Pole of the scope is EAST of the Southern Celestial Pole. The star, as it progresses West, drifts NORTH (Up) in the field of view, AWAY from the Southern Celestial Pole.

This gives us rule number two for drift alignment: If a star near the meridian drifts NORTH (up) in the eyepiece of the telescope, the SOUTHERN direction on our telescope axis is too far EAST of the SOUTH Celestial Pole, and the NORTHERN direction on our telescope axis is too far WEST of the NORTH Celestial Pole!

NOTE! :  Be very careful, because many manuals and instructions will be talking about the NORTHERN pole mis-alignment, and you may well be thinking SOUTHERN alignment because that's the direction you're looking!!

More important than the rules to be memorized, I hope that the reason the rules apply, makes sense to you!

NOTE # 2! :  You can easily get confused about which way the star is drifting, simply because your setup may or may not cause an inverted image.  To be sure, once you see a direction drift, just gently nudge the bottom of the optical tube UP a little, and see if that makes the star move 'South' according to your interpretation.  It had better, because you just nudged the tube NORTH!

NOTE # 3!  When you set about adjusting the East/West adjustment on your wedge, be certain as to which way to turn the knob!  It's all too easy to be thinking backward and turn it in the wrong direction.  Think about it for a bit, before you make the adjustment!

Let's move on.

The First Two Rules for the Southern Hemisphere.

Here we see a similar drawing as the previous one, except a person in the Southern Hemisphere would be looking NORTH to see the Celestial Equator, and it's the NORTH  Celestial Pole and the NORTH polar axis of his scope that's in front of him and below the horizon.  The SOUTH Celestial Pole, of course, is behind him and up.  Also, the  alignment star, which is rising from the East, will be moving from the observers RIGHT (East) to his LEFT (West).

In this example, the Polar axis is EAST (Right) of the North Celestial Pole.  The star, as it is watched, will drift UPWARD (South) in the eyepiece.

Southern Hemisphere rules #1 & #2

Rule number ONE for drift alignment in the Southern Hemisphere: If a star near the meridian drifts UPWARD  (South) in the eyepiece of the telescope, the NORTHERN direction on our telescope axis is too far EAST (Right) of the NORTH Celestial Pole, and the SOUTHERN direction on our telescope axis is too far WEST (Left) of the SOUTHERN Celestial Pole!

Rule number  TWO for drift alignment in the Southern Hemisphere: If a star near the meridian drifts DOWNWARD (North)  in the eyepiece of the telescope, the NORTHERN direction on our telescope axis is too far WEST (Left)  of the NORTH Celestial Pole, and the SOUTHERN direction on our telescope axis is too far EAST (Right)  of the SOUTH Celestial Pole!

Back to the Northern Hemisphere.

Once again we're back at our scope. And once again, unknown to us, it isn't really properly polar aligned as we had hoped.  Instead, we have the following condition:

What we're faced with this time is a condition in which, as we face South, the Southern pole on our scope is BELOW the Southern Celestial Pole.... or put another way, our Northern pole of the scope is ABOVE the Northern Celestial Pole.

If we look a star as it moves across our meridian, notice that there is VERY little Declination drift of the star.  That's fine, because we've already reserved that area of the sky for determining any left/right alignment error.  Instead, we can select a star that is fairly near the Eastern or Western horizon, and again, near the Celestial Equator.

If we watch for 'drift' of a star that is rising in the East, we can see that there's going to be a significant drift AWAY from the Southern Celestial Pole, or a NORTHERN (Upward) drift.  If instead, we use a star that's setting in the West, the star seems to drift TOWARD the Southern Pole, or a SOUTHERN (Downward) drift.

Either direction, near the East or West horizon, can be used for checking our up/down error.  It depends strictly on your choice, which is usually determined by which one will give you the best view.  Your East horizon may be blocked by houses or trees.  If so, just use the Western section of the sky, but always try to be fairly near the Celestial Equator.  You simply must remember which direction of star drift goes with which horizon.

This gives us rule number THREE for drift alignment: If a star near the EAST horizon drifts UPWARD (North)  in the eyepiece of the telescope, the SOUTHERN direction on our telescope axis is too far SOUTH of the SOUTH Celestial Pole, and the NORTHERN direction on our telescope axis is too far NORTH of the NORTH Celestial Pole!

Why is it recommended that all of your drift checks be made near the Celestial Equator? Won't some other area of the sky also show the error drift?  The answer is, yes it will.  The reason the Celestial Equator is chosen, is because that area of the sky will show the error much more quickly.  Zero degrees in Declination ... the Celestial Equator ... has the biggest 'diameter' of all of the Declination circles, so the drift error can be detected more quickly or more accurately.

It should come as no surprise to find out that when the South pole on the telescope is ABOVE the Southern Celestial pole, exactly the opposite conditions exist, so we have exactly the opposite directions of drift near the Eastern or Western horizon. The trick is, to be able to remember or figure out  which is which.  

This gives us rule number FOUR for drift alignment: If a star near the EAST horizon drifts DOWN (South)  in the eyepiece of the telescope, the SOUTHERN direction on our telescope axis is too far NORTH  of the SOUTH Celestial Pole, and the NORTHERN direction on our telescope axis is too far SOUTH of the NORTH Celestial Pole!

Note:  In reality, it's best to select a star that's perhaps twenty degrees or so above the horizon for your testing.  Your image is less likely to be distorted by heat waves from the Earth, or just plain poor 'seeing' in general.

A Quick trip back to the Southern Hemisphere.

Once again, we are looking North toward a star near the Celestial Equator, and we again are looking for the star to be fairly near either the Eastern or Western Horizon.  In this example, we see that the Polar axis of the scope is ABOVE the NORTHERN Celestial Pole, or BELOW the SOUTHERN Celestial Pole, which is behind us. In this case, if the star we use is near the EAST horizon, the star will drift DOWN (North) in the eyepiece.  If we are using the star that's near the WEST horizon, it will drift UP (South) in the eyepiece.

From what we've already covered about the actions in the Northern Hemisphere, added to the above information, we can state the next two rules for drift alignment in the Southern Hemisphere:

The Second Two Rules for Drift Alignment in the Southern Hemisphere.

Rule number THREE for drift alignment: If a star near the EAST horizon drifts DOWN  (North) in the eyepiece of the telescope, the NORTHERN direction on our telescope axis is too far ABOVE  the NORTH Celestial Pole, and the SOUTHERN direction on our telescope axis is too far BELOW the SOUTHERN Celestial Pole!

Rule number FOUR for drift alignment: If a star near the EAST horizon drifts UP (South) in the eyepiece of the telescope, the NORTHERN direction on our telescope axis is too far BELOW  of the NORTHERN Celestial Pole, and the SOUTHERN direction on our telescope axis is too far ABOVE the SOUTHERN Celestial Pole!

Tying it all together

You've seen how to detect and correct the various 'drifts' of a star for drift alignment.  There are a  few real world facts that should also be pointed out.

First, the best way for you to detect drift is to be using an illuminated crosshair eyepiece. Have the crosshairs aligned such that one set is parallel to the East/West movement of the telescope.  Do this by centering the alignment star, then running the scope back and forth in Right Ascension to be sure the star stays close to parallel to the crosshair. That way, a relatively small movement in Declination can easily be detected.

Another method that's often used if you don't have the illuminated eyepiece, is to position the scope so that the star you're observing is positioned at either the Northern or Southern edge of the field of view in a conventional eyepiece. That way, you can detect the North/South drift, seeing the small drift effects on the star.

Second, do not... NOT... worry about 'drift' in Right Ascension.  That has nothing whatsoever to do with Polar alignment, but simply has to do with the drive characteristics of your R.A. motor.  In fact, what you may well want to do is to 'guide' on the alignment star in  R.A., and hold it near the center of the crosshairs... or the edge of the field of view.... depending on the method used.

Third, once you've been through the two alignments, left/right, up/down, go right back to the beginning and repeat the procedure.  Unless you have your wedge PERFECTLY level.... not likely ... there will be interaction between the two adjustments.  That is, when you go back to the left/right adjustment, even though you thought you had it perfect the first time, it in all likelihood will need a small amount of re-adjustment.  Likewise after you've made this small adjustment.  It probably will have effected the up/down adjustment that you've just done.  Don't be surprised about it, and don't let it irritate you.  It's the nature of the beast.

Now, because of the fact that you'll most likely be going back and forth between the two adjustments, getting closer each time, it's easier on your nerves if you don't spend a lot of time on one particular directional adjustment before going to the other one.  You'll be ping-ponging between these two adjustments, if you're trying to get the drift down to as close to zero as you can.  If you keep going back to, say, the adjustment for left/right alignment of the pole that you're using as a reference, and finally get it to ideal, you may want to pull your hair out when you find that you have to go back and 'tweak' this adjustment again!  It's probably better, as you near the 'ideal' settings, to make a very small correction, watch it once to make sure you improved it some, then go to the other check and do the same.  That way, both adjustments will slowly get closer and closer to ideal, at the same time. (This is strictly a personal opinion, based on my own experiences, and you may not agree with it at all.)

Finally, there is a matter of 'how good must the adjustments be?'  That's really a subjective matter.  Naturally, in the ideal world, the answer would be that anything less than perfect isn't good enough.  But, at least where I do MY imaging, it's far from the ideal world!

If a person is doing strictly viewing, then Polar alignment isn't critical at all, so long as your 'go to' feature, if you have one, functions adequately.  For astrophotography or CCD imaging, it's quite another matter.  In my personal opinion, if a person has a permanent mount, then it's worthwhile to spend an evening every few months, to get the drift down to the minimum they can get, no matter what the scope application might be.  Under these conditions, a star viewed with high power would show no visible drift after 15 minutes or so.

On the other hand, if you are moving the telescope between viewing sessions, the limiting factor is all too often, the time it takes to get the drift minimized.  One doesn't want to spend most of the evening making Polar adjustments, only to have a short part of the evening left for imaging or photographing.

Even then, the amount of tolerable drift is going to vary with the type of imaging you do.  If you take a lot of relatively short, unguided images, then the accuracy of the adjustments would probably be determined by the field rotation one gets, while taking a full series of images of the same object.  

If, on the other hand, you self guide or auto guide, the factors to consider are going to be not only potential field rotation, but the extra work of guiding in both R.A. and Dec.  For a camera with self guide, your images will certainly turn out better if you don't require Dec corrections in your longest shot. Otherwise, you're potentially faced with camera over-correction, which can lead to trailed star images.

As you can see, on this subject, I leave it mostly up to the user.  That's the person that has to consider all factors, and by experience with time, will determine for themselves what the accuracy needed will be.  As for me, I have a permanent mount for my telescope, and I try to make sure that when doing CCD imaging, my self-guiding camera NEVER has to make Dec corrections.  Instead of using an eyepiece for determining the drift of a star, I simply select the star, begin to 'self guide'; with the Dec corrections turned off, and assure myself that after 15 minutes or so, there has been no more than approximately 1.5 arc seconds of drift in Dec.  That's usually good enough......... for me.