Tracking
Last updated
Last updated
So you want to track the stars now eh?
Makes sense! When the most reasonable exposure times you can achieve with a low focal length lens total in the 10's of seconds, you wont catch a lot of light. With a star tracker, you can expose for much longer.
"Tracking" simply means your camera will "follow" the stars. In reality, it is actually cancelling out the Earths rotation.
For starters, you will obviously need some form of tracker. If you are interested in potentially upgrading to a telescope and shooting some awesome deep-sky images at higher focal lengths, (above 135mm) you will need something even beefier. These types of mounts, called GEM's or German Equatorial Mounts, are more expensive than a tracker but are a wise next-step if you think you would like to do more than just widefield. Widefield images can easily be done with these kinds of mounts as well, but give you the option to upgrade to a telescope in the future.
If this is something you are interested in,
For general widefield purposes though, these products will do the trick, and won't make your wallet cry as hard. For a more detailed recommendation list, check out the widefield section on the page
Skywatcher Star Adventurer - Upgradable w/ counterweight bar, latitude adjustment wedge
Ioptron skyguider
Vixen Polarie Star Tracker
Or, Build your own!
Once you buy one, check back here on how to continue on. You may also be find these items used online for cheaper than the price from various retailers, and they usually work just as great. .
Now that you have your star tracker and brought it outside, you will need to polar-align it in order for it to work properly. This allows the axis of rotation on the tracker to effectively cancel out earths rotation. . Make sure your tracker is set to either N or S, for Northern or Southern Hemisphere.
For widefield purposes at low focal lengths, roughly polar aligning on the celestial pole usually does the trick. In the northern hemisphere, we are lucky to have Polaris, aka the North Star, to guide us near the celestial pole. It is slightly more difficult in the southern hemisphere due to there being no major bright stars near the pole, but the concepts are exactly the same.
The Celestial poles, both northern and southern hemisphere, are the axis of the earths rotation. They reside at the approximate latitude you live at, i.e, if you live at 40 degrees North (latitude), the celestial pole will be 40 degrees up in the northern part of the sky. At 40 degrees South, the same is true, but in the southern part of the sky. Longitude is irrelevant when it comes to polar alignment. I'm sure some of you might be having an Aha moment here!
While this guide was written with the Orion Sirius in mind, the same principle applies to sky trackers too. You will not have a declination axis to worry about if you are using a light tracker, so feel free to ignore that part. I recommend using a polar alignment app on your phone to find the position Polaris should be positioned in order to properly polar align. I am not from the southern hemisphere, so I am more unfamiliar with the methods used down there. That said, there are still apps that can help you. Just look up something along the lines of "Polar Alignment App" on your phone or PC, there will be many options to choose from. Choose something free.
Now, polar align your tracker or mount. If you move your setup when you're done imaging, you will need to do this again the next time you go out.
If you completed this, you are on track for taking long exposures! I generally like to take a 30s to 45s shot to ensure there is no trailing. If you get this far and don't have any issues, Congratulations! You are ready to start some serious exposure times. Start your exposures at whatever length you wish, I generally go for 2-3 minutes when i'm shooting widefield. You can choose to do longer exposures, but you still may suffer trailing due to gear errors and other inaccuracies in your tracker or in your alignment.
For Widefield, my setup is a Skywatcher Star Adventurer, Nikon D5500, and a few lenses, a 35, 50, and an 85. I use an intervalometer to choose exposure length and number of exposures.
As with everything, this hobby takes time to learn and get used to. Don't be disappointed and throw your gear into the trash can if you don't get good results your first time. I certainly didn't.
Hopefully this guide was helpful for you.
Good luck!
You will want to align your tracker or mount on these poles in order to achieve a desirable alignment. There are several methods of polar alignment, but the easiest is usually software assisted. In the case of light trackers, use the included polar scope to accurately align your tracker. A .
I have seen people get great results with a 135mm lens as well. Higher than that, and you may want to start looking at mounts like the Orion Sirius or Atlas, or the Skywatcher HEQ5, EQ6, or EQ6r. Do your research on Equatorial mounts, and feel free to visit /r/AskAstrophotography, or hop into our if you have any questions.