Drift Alignment Method
This guide was written up by a friend and fellow member of the astronomy clubs that I am associated with. This is a guide for Equatorial mount owners without GoTo capabilities but you can follow this guide if you have a motor on the RA axis.
All credit goes to Myles Gibson of Worthing Astronomers for creating this guide.
Getting the most out of a manual EQ mount:
I decided to write this little document to hopefully help some beginners who have purchased an equatorial mount for their telescope, but don’t have a GoTo, or any electronic tracking.
I bought my telescope a Celestron Astromaster 90 which had an EQ mount but it lacked a motor drive. The mount was not able to get a ‘GoTo upgrade’ so I had to use it completely manually. It was a pain at first, but once I learned how to use it I have been getting better and better at finding objects in the night sky, and being able to track them. This is a guide for those who use their EQ mount totally manually. It will be broken down into 2 parts.
The first is ‘How to reliably polar align your scope and the second will be Finding and tracking night sky objects. Please bear in mind that these are just my preferred methods and it works for me. There may be other methods that work for you, but this should hopefully prove a good starting point.
How to reliably Polar align your scope:
This is the most important bit. I used to find that once I found an object, I could keep it in the FOV by using the fine adjust RA (Right Ascension) knob. However, after a while the object would always drift either up or down and I would have to use the Dec (Declination) adjust to keep it in the center.
I have been using the ‘drift method’ to enable myself to Polar Align my scope reliably and allow me to leave my scope (for a tea/coffee/chat) and return a few minutes later and adjust only the RA knob to find my object is still centered.
So how is this performed? It can be done in a few easy steps. It should be noted that this method can take a while and can sometimes require patience!
1) First give yourself a rough Polar Alignment by eye. Do this by pointing the front of your mount towards Polaris. Most EQ mounts will have an arrow or some indicator as to where the front is.)
2) Next point your scope SOUTH by loosening the clutch knobs and moving the scope without moving the tripod and find a bright star. The lower in the sky, the better. Tighten the clutches and center this star in your eyepiece.
3) You now need to track the star and watch to see if it drifts up or down. If you have a cross-hair, this is very easy, just center it and watch. If you do NOT have that luxury, there is a good way to do it (that I use).
4) Center the star, then put in your strongest powered eyepiece in.
5) Now defocus it a little so it’s a bit blurry (just to make it bigger and more noticeable)
6) Use your Dec and RA knobs to place the star at the very top of your eyepiece, in the center.
7) Wait a minute then use the RA knob to bring it back into view. If you cannot see it any more, it has drifted UP. If it is closer to the center of the eyepiece, it has drifted DOWN. Once you know the drift of the star, make your adjustments.
8) If the star has drifted UP, your alignment is too far WEST. You need to move your mount slightly to the EAST.
9) If the star has drifted DOWN, your alignment is too far EAST. You need to move your mount slightly to the WEST..
10) Repeat the previous step and check the drift of the star again. If it still drifts up or down make more adjustments and repeat until the star no longer drifts. Now find a bright star low in the east. Repeat the drift tracking technique again and watch the drift of the star.
11) If the star drifts UP, your latitude setting is too high, you need to move it down slightly.
12) If the star drifts DOWN, your latitude setting is too low, you need to move it up slightly.
13) Once the star drift is under control, double check with a southern star to ensure your tracking is still good.
Congratulations, you’re now guiding!!!
Finding and tracking night sky objects:
Now, of course there are many methods for doing this, but the method I am going to use is the setting circles. Each EQ mount will have setting circles in both RA and Dec axis’. If your mount is properly Polar Aligned, this can be a powerful tool in aiding you to find night sky objects.
It should be noted the setting circles will not be 100% accurate, but with a decent FOV the desired object should be viewable, if not centered.
1) Find yourself a ‘starting star’. This star should be bright and easy to find.
2) Center it in your eyepiece then look up the RA and Dec co-ordinates. Move your setting circles to match the co-ordinates for that star. The RA setting circle will have 2 sets of markings. One for the Northern Hemisphere, and one for the Southern Hemisphere. The Northern one should be the top one, and Southern should be bottom. This can vary between models.
3) Once you have set your co-ordinates, look up the RA and Dec of your target object that you wish to view.
4) Before moving to that object, double check your starting star is centered and the RA and Dec correct.
5) Loosen the Dec adjustment on your mount, move the telescope to match the Dec of your target. Tighten in place when you reach the target setting. This is where the setting circles can be a bit inaccurate. The Dec setting circle has a lot of close together markings, you should try to get as close as possible.
6) Loosen the RA adjustment on your mount and move the telescope to match the RA of your target. Tighten in place when reached.
7) Look through your eyepiece, the target object should be viewable. If it is outside the FOV, loosen the Dec adjustment on your mount and slowly move it and the object should come into view. It is usually the Dec that is off.
8) If the RA is also off, move the telescope along the RA line until the object is in view.
9) Now you can center your object and track it across the night sky!
10) If you were quite far from your target, check your polar alignment.
I hope this has been of use to any beginners who wanted a few hints on getting the most out of their EQ mounts without having to spend a lot of money upgrading to a GoTo! This does take some patience and practise, but once you get it, you’ll have a lot of fun!
Paul's Astrophotography © Paul Ibbitson 2023