Polar alignment is possibly the most confusing subject in astronomy and when you are dyslexic like me it is even more baffling to get your head around so hopefully, this will help some of you who may be struggling. So let's begin with some basics.
When you go out and look up at the stars you will notice after 20 minutes or so that they are moving rotating around a central point in the sky this central point is very close to the star Polaris which is why we use it to line up our telescope mount which is called Polar alignment.
To illustrate why Polar alignment is so important to getting good Astro images all you need is a compass and a pencil. Draw a circle like the one below and mark the central point and a star on the outer circle which represents the star rotating around the celestial pole in the sky.
Ok now draw another circle but put it just off centre and overlapping the first one. The red circle below represents your telescope mount not lined up with the celestial pole the point at which all stars are rotating around. The smaller red circle is your camera and its field of view. Notice that as your mount tracks the star as it rotates the star will drift off to the side then as your telescope tracking motor follows the star it will drift back again and to the other side. So you can see why it is important to get your polar alignment as accurate as possible if you want to avoid getting star trails in your images.
You can see this for your self when going through your images in your camera I use a DSLR and when my polar alignment is not spot on the images appear to drift to one side then drift back again. You can get away with a 30-sec exposure but any longer and you will get star drifting in your image.
Now of course if you are not correcting these errors with a guide scope and simply using a tracking motor on your mount this becomes one of your main issues when taking images. So the way to solve it is to make sure you do the best Polar alignment that you can do.
If you are using a simple set up with say a telescope mount like the EQ5 mount fitted with a dual-axis motor kit to track the motion of the stars as they move across the sky and nothing else then you must make sure your Polar alignment is the best you can get it. There are many tutorials on how to do this online so I will not bore you with the details but just point out a few things that might trip you up.
Your telescope must be coliminated correctly I recommend using a lazer colminator to insure all the mirrors are in line and that your colimation is perfect.
Next on my list would be make sure your telescope mount is level and check it with a spirit level then check all the bolts and make sure nothing is loose.
Also, make sure that your polar scope is perfectly aligned as well this means taking some time to check the reticule inside is perfectly lined up.
Also, check that your mounts gears are not sticking and adjust them so all slack or binding is got rid of.
As you progress with Astrophotography you will more then likely get your mount linked up to your computer or laptop and take advantage of all the software out there but if you're just starting out and want to take great images of the night sky this is all you need I have a skywatcher 200p and an eq5 mount with a Canon 450d second hand and a T adapter to connect it to the telescope a batinov mask to add focusing and a dual-axis kit.
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