|This is quick guide
to simple polar alignment with an equatorial mount. Its designed only to get
rough polar alignment suitable for observing.
Newcomers to astronomy are quite often easily put off from equatorial mounts by being told they are complex to set up and use. My own personal experience is that they are no more difficult to manage than a standard alt-azimuth and have the advantage that when polar aligned they make life easier when your observing as you have only one control to handle to keep the telescope pointed at an object.
Beginners are often frightened by the idea of 'Polar Alignment' as it can seem quite complex. Its actually fairly easy. This guide will talk you through a rough Polar Alignment that will be easily good enough for observing with. If you want a more accurate alignment for astro-photography then you could start with my guide for aligning the HEQ5 which will give a more precise alignment. for full on accuracy you will need to carry out a star drift test. That isn't covered in either of my guides as I dont need that level of accuracy for observation.
Before you start the guide it may be useful for you to familiarise yourself with an equatorial mount. You can see a fairly simple equatorial mount with its main components listed HERE.
|Why Polar Align
? - As the earth rotates the stars appear to cartwheel through the sky
above. By aligning the telescope to a fixed point in the sky which isn't moving
allows you to track objects using only the Right Ascension control. The Right
Ascension movement compensates for the earths movement and allows the telescope
to 'track' an object. The part of the sky which doesn't move is of course the
North Celestial Pole ( if your in the Northern hemisphere ) which is rather
like a hub around which the stars appear to rotate.
Polar alignment is simply the process by which we aim the telescope at the NCP. In fact in this guide we wont be aiming at the NCP we'll aim at the Pole Star - Polaris. Luckily in the Northern Hemisphere Polaris is very close to the NCP and provides a good enough 'fix' for observing.
|Finding Polaris - Method 1|
|Finding Polaris - Method 2|
|While the method above is the simplest and one that most people
who have been doing astronomy for more than a few weeks can achieve easily its
none the less quite tough on the complete novice. My experience has been that
few people when they start in the hobby can identify much in the night sky with
any great certainty. I know I couldn't !
Heres a method that you can use to get you started until you can easily spot Polaris from a little experience.
You will need a compass to do this or at least have access to an on-line map that will give you a clue where North is. Google Earth is good, you may just know your own area well enough to know where North is. If not a cheap compass is all you need. If your using a compass make sure there's nothing metal about for 20' either side of you and that includes your telescope.
Find North and then loosen off the azimuth nut on your telescope mount and rotate the mount until the RA axis faces North. This is shown in the pictures below. Now lock your azimuth adjuster. The azimuth adjustment is the one that allows your telescope to turn right or left.
|Now you need to set your latitude. For this you will need something like Google Earth or a map. If your in the UK you can just set the latitude for 51 degrees. To set this you will need to unlock your latitude lock as shown below left and then adjust the mounts latitude using the altitude nut as shown on the right.|
|Adjust the altitude nut until your latitude is indicated on the latitude scale. For my location in the UK I have set up for 51 degrees as shown in the picture below on the left. Finally lock the latitude as shown below right.|
|Your mounts RA axis is now roughly pointing to Polaris, Now we
have to make sure the telescope is in line with the mounts RA
Note: Its worth mentioning that on many low cost mounts the Altitude/Latitude scale can be less than accurate. Some users report the scales being off by as much as 10' on the scale. So if you dont find POlaris at 51' exactly then try moving the scopes altitide/latitude. Even more upmarket mounts can show a difrference between the scale and the actual position of Polaris.
First loosen the RA and DEC lock knobs as shown below making sure you have a hold of your telescope. I am assuming if your reading this you most likely have a small, lightweight scope and have already balanced it on the mount. If your haven't then you should check how to balance your telescope.
|With the RA and DEC lock knobs loosened rotate your telescope until it sits 'over' the mount as shown below. Your Declination scale may have been preset at the factory in which case it should read 90 degrees, if not ignore the DEC scale and just set the telescope so that its in line with its RA axis. You can see on the picture to the left below that the telescope tube is in the same line/direction as its RA axis. Now lock both the RA and DEC lock knobs down.|
|If your using your telescope in the backyard simply make a note of where the telescope was pointing when aligned to Polaris. In my house I know the rear wall faces North almost exactly. Using that and leaving the latitude adjustment alone I can be set up in minutes. Its not a perfect alignment but it will be perfectly adequate for most observing needs with an equatorial mount.|
|That's it ! I hope you have enjoyed the guide an I hope its of some use to beginners out there. May all your stars be visible all the time.|
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