The SkyWatcher Star Adventurer PRO has one particular feature that sets it apart from all the other trackers on the market.
Ironically, this is the very same feature that most people dismiss.
I am talking about the Graduation Circles at the back of the tracker.
The Graduation Circles at the back of the Star Adventurer
What Are The Graduation Circles For?
These circles are there to allow you to polar align the Star Adventurer to the Northern Celestial Pole (NCP) without the use of a computer or an app.
All you need to know is your latitude, your longitude, the time of the day and the date.
Why Should You Bother Using Circles Instead Of An App?
That is totally up to you, but since you paid for them, you may want to at least understand how they work.
First of all, whatever method you use, you have to have the reticle inside the polar scope calibrated. This means that if you set the Star Adventurer to Midnight October 31st, with the Meridian indicator set to 0, the line 0-6 of the reticle must be vertical to the ground.
Provided you level the mount.
If all is ok, the reticle of the Star Adventurer will be oriented as in the app you want to use.
So, Is The App More Precise Than The Graduation Circles?
The problem is how precisely you can level the mount.
By fiddling with the tripod legs an looking at a 3D bubble level, the precision is rather coarse. Still, you can get away with short focal lengths, but if you are thinking to use a 200mm lens the accuracy in leveling the mount must be higher.
But both methods relying on leveling the Star Adventurer to the ground for precise polar alignment.
While for a mount that is already aligned to the celestial pole, have it leveled to the ground does not matter, with the StarAdventurer leveling the mount is a requirement for achieving the precise polar alignment.
And this is due to the particular way the reticle works: it uses your coordinates, time and date to show you the position and altitude of Polaris above the horizon.
I know people are skeptical about this, so I explain in this post why you need to level the Star Adventurer if you use the circles or the app.
The Tree Graduation Circles
The Star Adventurer has three graduation scales:
the Time Graduation Circle, attached to the body of the mount;
the Date Graduation Circle, which rotates with the polar scope;
the Time Meridian Graduation Circle which ”sets” your longitude in terms of offset from the local standard time meridian;
The Graduation Circles of the Star Adventurer. What I friendly call “Time Zone Scale” is used to set the offset from the LSTM.
Of all the Graduation Circles, the most obscure of all is Time Meridian Graduation Circle.
I don’t want to make a big lecture about this, and for polar aligning all you need to know about this is:
There is an LSTM every 15º of longitude;
The longitude for your LSTM can be found by multiplying your GMT time zone times 15;
The offset is your longitude not with respect to the Greenwich Meridian, GM, but with respect to your LSTM.
Every 15º of longitude there is a LSTM.
Here is a real-life example.
I live in Brussels (Belgium). Because my GMT time zone is GMT+1, the longitude for my LSTM is: +1 * 15º = +15º E.
The “+”, in fact, means I am Est of the GM. “-” GMT time zones are West of the GM.
I live in Brussels and the longitude of my location is 4º E. This is also with respect to the GM. But because I am 4º E and my LSTM is 15º E, my offset from the LSTM is 11º W (as I am closer to the GM than my LSTM).
Next, you have to remember to always use the Standard Time when polar aligning.
Again another example to clarify.
At this time of the year, in Belgium, we have daylight saving time. For this reason, while my wristwatch is telling me my local time is 2:30 p.m., the standard time for my location is actually 1:30 p.m.
In winter, without daylight saving time, the time shown by my wristwatch is the standard time.
And this is all there is to understand in order to polar align the Star Adventurer using the graduation circles. How hard can this be? ;)
Polar Alignment In Practice
So, how do you polar align the Star Adventurer by using the Graduation Circles?
Here the four basic steps to do:
Level your mount to the ground as best as you can. A leveling platform placed between the tripod and the wedge can help;
Grab and hold the mounting platform so that the polar scope cannot rotate and rotate the Date Graduation Circle until the Meridian Indicator shows the proper offset of your location from your LSTM;
Align the mark for the day of the month on the Date Graduation circle to that of the time of the day on the Time Graduation Circle by rotating the polar scope;
Look through the polar scope and put Polaris on the mark that corresponds to the number 6, wherever it is. For your reticle orientation, the number 6 of the clock may not be located “at 6 o’clock”;
After you set the Graduation Circles for your location and time, put Polaris on the mark for the number “6”.
In the image below, I configured the Star Adventurer to 1 a.m. November 30th, for Brussels (11º W of the LSTM).
My offset from my LSTM is 11ºW (red line) and the current time and date is 1 a.m. (green line) of November 30th (yellow line).
After doing this a couple of times, you will do your polar alignment in no time.
The Story Behind The Graduation Circles
Before concluding this post, I want to spend a few words on why we need those circles and why is it we need to place Polaris always on the 6 of the reticle.
The Star Adventurer is an equatorial mount, meaning that the payload you mount on it looks at the sky using the global right ascension and declination as stellar coordinates. These do not depend on your location on Earth.
The mount itself, though, is mounted on an equatorial wedge, which essentially is a manual Alt/Az mount. The tracker on the wedge looks at the sky (and at Polaris in particular) using the local Altitude and Azimuth stellar coordinates.
The equatorial wedge of the Star Adventurer (Scheme from the manual).
These coordinates are local, as they not only depend on your latitude and longitude, but also by the time of the day and date.
The controls on the wedge move the Star Adventure in Altitude and horizontally to bring Polaris in the right position.
The “right position” for Polaris depends on your position on Earth (latitude and longitude), as well as the current time and date.
Your latitude is controlled by the altitude knob on the wedge, while the longitude, is set by considering the offset of your location with respect to your LSTM.
Finally, by setting the current time and date, the position of the “6” in the reticle reveals the current position of Polaris around the true NCP.
A Short Video To Illustrate The How The Graduation Circles Work
Here is a short video I made to summarize what I wrote in this post.
Related Topics
Learn More About Polar Alignment
if you want to know more about why polar alignment is important and how does it work, I wrote a very detailed, but easy reading, guide here on NightPixSky. If you are new to astrophotography, you should have a look at that guide.
Learn More About Your Star Adventurer
Do you want to be a happy owner Of the Skywatcher Star Adventurer? If so, have a look at the Ultimate Guide To The Star Adventurer I wrote for NightSkyPix.
The mount is not difficult to use, but with a few extra tips and tricks, you will be able to get the most out of it with ease.