Star Tracker Tutorial

November 14, 2017  •  21 Comments

Tired of grainy Milky Way photos?  Don't want to spend $2,000 on a new wide angle lens?  A star tracker is the easiest, and most cost effective way to capture higher quality nightscapes!  These devices move the camera at the same speed as the stars, allowing you to take much longer photos without any star trails.  The key to this process is a proper polar alignment.  The star tracker must be pointed directly at Polaris, the North Star.  (Or, if you are in the southern hemisphere, Sigma Octantis.)  This tutorial will cover everything you need to know about using a star tracker, from choosing the correct model, to setting it up, and even post processing!

Before we get into the tutorial, I thought I'd show some images taken with the my iOptron Skytracker Pro and SkyGuider Pro

Andromeda GalaxyAndromeda GalaxyUsing a Tamron 70-200mm and iOptron Skytracker Pro I was able to capture the Andromeda Galaxy Kenosha PassKenosha PassThe Milky Way rises over Colorado, as seen from Kenosha Pass. Trillium Lake - MidnightTrillium Lake - MidnightThe Milky Way shines brightly over Trillium Lake. Mount Hood can be seen in the distance The Galactic CoreThe Galactic CoreA detailed look at the Milky Way galaxy, the Lagoon Nebula and Trifid Nebula can be seen as well

 

Is There Really That Much of a Difference?

Many people have asked whether or not a star tracker really makes that much of a difference when doing Milky Way photography.  Especially considering the fact that there are great photo stacking applications that can reduce noise very efficiently.  In my experience, a properly aligned star tracker will have a massive impact on image quality.  Let's take a look at a few comparison images to see the difference.

In the comparison below, we are looking at an ISO 12800, f/2.8, 10 second image vs a tracked ISO 800, f/2.8, 4 minute image.  Even from afar, you can clearly see a difference in color and image quality.

 

Untracked
Tracked

 

Let's take a closer look next.  When zoomed in, the untracked image is a grainy mess, while the tracked image looks beautiful!  Notice too, how the magenta color in the Lagoon Nebula comes through much better in the tracked image.  One last thing to note - The tracked image was a 4 minute exposure.  I could take an even longer photo, up to probably 6 minutes, without star trails.  This would result in even more detail, color, and less grain.  However, the amount of Hot Pixels would increase too.

 

Untracked
Tracked

 

 

 

Choosing a Star Tracker


A quick Google search will yield at least 3 potential options for a good star tracker.  Some of the most popular star trackers include the iOptron SkyTracker Pro, the iOptron SkyGuider Pro, the Sky-Watcher Star Adventurer, Star Adventure Mini, and the Vixen Polarie.  There are even more mounts out there, but those are more for telescope users.  I'm focusing on photographers who are just getting into astrophotography.  Let's try to make the decision a bit easier.  There are a number of factors to consider before you purchase your star tracker.

I recently created an overview of the iOptron SkyTracker Pro, which I would recommend watching first.  This will give you an overview of how most star trackers actually work.

 

Weight Limit

The most important thing to consider before buying your first star tracker is the total weight of your camera gear.  That includes the camera body, any L-Brackets or tripod plates attached, your lens, and the ballhead you will be using.  One of the main differences between the different star trackers is how much weight they can handle.  If you only have an entry-level DSLR and a kit lens, or mirrorless setup, nothing special is required.  However, if you have a bulky full-frame DSLR with a large wide-angle or telephoto lens attached, you will want a star tracker that can handle an increased payload.  If you try to put too much weight on your star tracker, it will fail to track.

I personally own the iOptron SkyTracker Pro, which has a 6.6 payload capacity.  However, in the small print, iOptron specifies "for camera rigs up to 2.6 pounds, or with an optional counterweight kit - for rigs from 2.6 to 6.6 pounds, including the lens."  2.6 lbs is nothing!  My D750 alone weighs 1.7 lbs!  iOptron does sell an optional counterweight, which will allow the star tracker to operate with a heavier payload (in this case, up to 6.6 lbs).  I recently purchased this counterweight and found it to be a pain to use.

Having used the SkyTracker Pro's counterweight kit for a big lens, I can't recommend it.  If you plan to use a 70-200mm or larger lens, you should opt for a different tracker.  The SkyTracker Pro simply isn't designed to handle such big lenses, even with the counterweight.  The SkyGuider Pro is a much better choice for serious astrophotographers.

The SkyGuider Pro does come with a counterweight kit included, as seen in this video.  If you use that counterweight system, you can push the SkyGuider Pro up to 11lbs.  I recently purchased the SkyGuider Pro and I can now use the Tamron 70-200mm lens properly.  In fact, I actually need 2 counterweights to properly balance this lens.  

To give you some first hand feedback, let's take a look at my gear weight:  

  • Nikon D750: 1.7 lbs
  • Kirk L Bracket: 0.27 lbs
  • Acratech GP Ballhead: 1 lb
  • Tokina 100mm: 1.2 lbs
  • Nikon 14-24mm: 2.18 lbs
  • Tamron 70-200mm G2: 3.28 lbs
  • Tamron 150-600mm: 4.3 lbs

So, with just my D750 (with L bracket attached) and my ballhead, I'm already at the 2.6 lb limit of the Skytracker!  With that said, I've managed to shoot 60 second exposures at 100mm without tracking errors.  That would put me nearly 2 lbs over the weight limit, while still getting good results.  With the 14mm lens, I was able to successfully track up to 4 minutes without any problems. 

 

Counterweight Kit

Once I realized just how much my camera gear actually weighed, I decided to buy the optional counterweight kit for the SkyTracker Pro.  It consists of 3 pieces: a screw with a rotating lever attached, the rod that holds the counterweight, and a dovetail bar that holds everything together.  The initial setup is not hard, it took me about 5 minutes.  You can read iOptron's official instructions here or watch my video at the top of this post for complete installation instructions.

Here's my very short review of the counterweight kit: "Don't buy it!"  I've honestly had nothing but problems using the optional counterweight for the SkyTracker Pro.  If you plan to use a 70-200mm, or other large lens, buy the SkyGuider Pro, or similar model, instead.  The SkyTracker Pro simply wasn't designed to handle such big lenses.  The counterweight kit can't change that fact.

Check out this video, which shows the SkyGuider Pro with the included counterweight.  As you can see, it is easy to balance the counterweight and use heavy lenses, unlike the SkyTracker Pro or Vixen Polarie.  I recently purchased the SkyGuider Pro and was surprised by just how much weight is needed to properly balance a 70-200mm lens.  I need 2 of the three pound counterweights to balance my 70-200mm lens.  In hindsight, there's no way I could have gotten repeatable, stable frames with the SkyTracker Pro.  The image below shows my balanced setup using the SkyGuider Pro.

 

SkyGuider ProBalancing my Tamron 70-200mm on the SkyGuider Pro

 

Ease of Use

Another thing to consider when purchasing a star tracker is how easy it is to setup.  There are 3 critical factors to a good alignment.  The star tracker must be level, it must be pointed directly at the North Star, and the weight must be balanced properly.  The iOptron SkyTracker Pro and SkyGuider Pro have a few features to make this relatively easy.  First, they come with their own base that can be attached to directly to your tripod.  The base includes a bubble level and latitude adjustment.  Second, they both include a polar scope.  You can look through the scope to help find the North Star and ensure a precise alignment.

To get your Star Tracker pointed directly at the North Star, you'll need to do 2 things.  First, determine your latitude.  I recommend the Photographer's Ephemeris App.  It will show your current latitude in the upper right corner of the app.  Then, you can dial that in on your SkyTracker/Guider Pro base easily.  Again, watch my YouTube tutorial video to see that.  Once the latitude is correct, you'll need to move the tripod so the Star Tracker is facing North.  From there, use the Polar Scope or Quick Sight Hole to find the North Star.

Alternatively, you can attach the star tracker directly to a ballhead.  This gives you the freedom to move the star tracker where ever you need to.  However, that method requires 2 ballhead, since you will need another ballhead to hold the camera.  I like using the SkyTracker Pro's included base.  I find it makes accurate polar alignments relatively easy.

You can use the thumbscrews at the base of the SkyTracker/Guider mount to move the star tracker left or right.  This will help with precise alignments.  You can also use the <> button on the back of the SkyTracker Pro to rotate the camera mount either clockwise or counter-clockwise.  Using the <> button allows you to reframe your galaxy or nebula without having to move the ballhead.  This is explained better in the video embedded near the top of this blog post.

The Vixen Polarie does not come with its own base.  Therefore, you will need 2 ballheads to make it work.  One ballhead would hold the Polarie on the tripod, the other would be attached to the Polarie's rotating mount and used to hold your DSLR.  This could make alignment more difficult.  You can no longer just dial in your latitude and face the tripod to the North Star, like the iOptron models.  You will need to carefully move the ballhead around and do a lot of tweaking.  The Polarie does not have a polar scope either, only a quick-sight hole.  This will likely make alignment harder as well.

Having used both the SkyTracker and SkyGuider, I've noticed that it is easier, and faster, to get a good alignment with the SkyTracker Pro.  The SkyGuider Pro is a bit more difficult.  I suppose this could also be because I'm using the SkyGuider to do more deep-space astrophotography, and therefore I'm using larger lenses with much more zoom, which requires a lot more precision.  Bottom line, if you only plan to do wide-angle shots (50mm or wider), the SkyTracker Pro will likely work better for you.

I recently had the opportunity to play around with the Star Adventurer Mini and was surprised to learn it has its own app!  With the SynScan Pro app, you can control various features of the star tracker.  I will be spending more time with this star tracker in July, and will report back with any updates.

 

Battery

This one comes down to personal preference.  The Vixen Polarie and Sky-Watcher Star Adventurer both use AA batteries, while the iOptron Skytracker and SkyGuider have a rechargeable battery.  In my experience with the SkyTracker Pro, I don't mind the rechargeable battery.  I know I can always charge it while I'm driving to my photography location!  The battery does last a long time, and you shouldn't have a problem using the star tracker all night long.  However, if you end up killing the battery overnight, or forget to charge it, you're out of luck.  It's also possible that your internal battery can get damaged or fried.  With the Vixen Polarie though, which takes AA's, I would never have to worry about a low battery; I could simply pop in some fresh AA's and keep shooting.  Consider which option would work better for you.

 

Size / Weight

If you plan to take your star tracker on backpacking or hiking trips, you're probably gonna want a small, light weight model.  Honestly, most of the star trackers on the market are small, compact, and lightweight.  However, the optional counterweight kits are quite heavy and you will probably want to leave those behind on hiking / backpacking trips.  Having tried a few different star trackers, they are roughly the same size and weight as well.  The SkyGuider Pro is made of a solid metal material though, while the SkyTracker Pro is formed of a lighter plastic.  I really haven't done any backpacking yet with a star tracker, and I prefer doing my star tracker images near my car.

 

Alignment

This is arguably the most important factor when choosing a star tracker.  If it's a pain to align, you're never going to get the sharp stars you want!  Remember, getting the star tracker level and pointed at the North Star is critical for a good alignment.

If you still aren't sure how to find the North Star, I recently made a quick image guide.  You will need to find the Big Dipper first.  Then draw a line out from the upper right star in the Big Dipper, it will point directly to the North Star.  Click here to see the image guide.  All of the stars in the sky will appear to revolve around the North Star.

The Vixen Polarie only has a small hole to help with alignment, it does not come with a polar scope by default.  However, you can buy one for an additional fee.  It will slot into the quicksight hole.  The SkyTracker Pro also has a quick-sight hole, similar to the Polarie.  In my experience, it was very hard to use the quick-sight hole to align.  I wouldn't want to be stuck with this method. 

Finally, for extremely precise alignments you will need an app.  This app will show exactly where to position the North Star (or Sigma Octantis) in your polar scope reticle.  For Android users, Polar Finder App will do the job.  Make sure to change the reticle to iOptron in the wrench menu.  Those of you on iPhone can download the official iOptron Polar Scope App.  In either app, you will see a green dot somewhere in the reticle once it loads in your location data.  You will need to position the North Star in the same spot on your polar scope reticle for precise alignments.  If you are using a wide angle lens, you really don't really need to worry about being that accurate.  Again, check out the video above for more information on using the app.

Having used both the SkyTracker Pro and SkyGuider Pro, polar alignment is very easy with both devices.  The SkyGuider Pro is a bit more confusing at first.  You need to rotate the front of the SGP in order to align the reticle inside the polar scope; the red light only turns on at very specific spots while turning.  It's possible that your SGP polar scope may have some problems when doing this.  If you think you are experiencing problems with your SGP polar scope, click here to read more

*I will be uploading a full-length SkyGuider Pro tutorial soon which shows this everything about the device.  

 

My Recommendation

Let me first start by saying I've only actually used the iOptron SkyTracker Pro and SkyGuider Pro so far.  Therefore, I can't definitively say which tracker is best.  I plan to spend some more time using the SkyWatcher trackers during the summer of 2018 and will update this blog post accordingly.

As of right now, I would recommend the SkyGuider Pro for just about everyone.  The relatively high weight limit, solid build quality, included counterweight kit, and scalability of this star tracker is a great option for anyone getting more involved in nightscapes or astrophotography.

If you just want to do wide angle landscape photos, the SkyTracker Pro will work great!  (Just remember to skip that optional counterweight kit!)  The SkyTracker Pro is lightweight, very easy to align, and does a great job with wide angle lenses.  If you want to get more into deep-space astrophotography, I would highly recommend the SkyGuider Pro instead.  The included counterweight and improved mount on the SkyGuider Pro will be critical for successful deep-space astro photos.  Keep in mind, you may even need to buy an additional counterweight to properly balance a large telephoto lens.  

 

 

Aligning the Star Tracker


Now that you've selected your star tracker, it's time to align it properly.  I will be using the SkyTracker Pro for demonstration.  Regardless of which tracker you choose, the process will be very similar.  Again, I recommend watching my YouTube tutorial that shows you how to do these steps on the Skytracker Pro.

I recently created this tutorial video which shows you exactly how I setup my SkyTracker Pro at night.  This process will be roughly the same, regardless which Star Tracker you have.  I've also included a written guide below the video.

 

And here is the written guide:

  1. Find North Star  
  2. Setup tripod and attach your star tracker
  3. Level the tripod and make sure the star tracker is facing North
  4. If using the iOptron models, adjust the base for your current latitude  (Use TPE to determine latitude)
  5. Look through Polar Scope hole / Quicksight hole, make sure North Star is visible
  6. Attach Polar Scope
  7. Open App and verify proper North Star location on reticle
  8. Look through the Polar Scope and look for the North Star
    1. Use the thumbscrews to rotate the star tracker precisely left or right
    2. May also need to re-adjust laltitude
    3. Make sure Polaris is in the same spot in the Polar Scope reticle as in the App

Alright!  At this point, the star tracker should be aligned properly.  Remember to tighten all the screws back down.  At this point, be careful not to move the tripod or star tracker.  Now we're ready to finish the star tracker setup and begin taking photos!  

  1. Attach your camera gear to the star tracker
  2. Double check ballhead is secure!
  3. Turn on Live View, zoom in, and focus lens to stars
  4. Take a test shot to check composition and focus
    1. I use ISO 12,800 and a 15 second shutter speed (faster may be needed for telephoto lenses)
  5. Look through the Polar Scope or quicksight hole again, make sure the North Star is still there
  6. Turn on the Star Tracker
  7. Take a long test photo to verify stars are sharp and tracker is properly aligned
  8. If stars are blurry, you need to troubleshoot

There are usually 3 reasons why you are still seeing star trails.  First, make sure the star tracker is turned on.  Second, make sure you have the North Star visible and aligned properly in the polar scope.  Third, check your counterweight.  If you are not using a counterweight, it's possible that your camera gear is too heavy for the mount.  If you do have a counterweight, it's probably unbalanced.  You may even need to remove the counterweight entirely and just leave the counterweight rail attached, if you have a fairly light setup.

  1. Take another test shot
  2. Stars are now sharp
  3. Set camera to Manual Mode, Shutter Speed to Bulb.  Enable Wireless Remote or attach wired remote
  4. Get out your smartphone so you can time the exposures.  Alternatively, set your external intervalometer settings
  5. Turn on Long Exposure Noise Reduction if taking 1 minute+ photos
  6. Now we're ready to take a long exposure!! 
  7. Depending on focal length and alignment accuracy, take your photo
  8. Here are some rough guidelines:
    1. 30 seconds for 200mm / 1 minute for 100mm / 2 min for 35mm / 4 minutes for 14mm
  9. Use smartphone to time your exposure, or use your wired remote
  10. Check to see if stars show motion.  If so, use shorter time.  Double check the Star Tracker is actually turned on.
  11. After taking your tracked photo, turn off the Star tracker.  Now take another exposure, of equal length.  You can blend the foreground and stars later.
  12. If you are doing deep-space astrophotography, take 10+ more photos to blend in post-processing and reduce noise


Other tips:

  • Turn off tracker when not in use to conserve battery
  • Don't move tripod!  Otherwise you'll have to realign.
  • Take multiple photos.  Can blend them in post to reduce noise and increase detail
  • I recommend 4 minute exposure at ISO 800 for foreground photo on a moonless night.  Should capture plenty of light.  Make sure Star Tracker is turned Off
  • Polar alignment precision is unnecessary when shooting wide angle photos (~14mm - 35mm), as long as you're close you should be fine!

 

 

Post Processing


Hopefully you remembered to take a long exposure for the stars, as well as a long exposure for the foreground!  I recommend ISO 800, f/2.8, and a 4 minute Shutter Speed to capture enough light for the foreground.  This will make a huge difference in the amount of light gathered compared to an ISO 6400, 30 second photo!  Trust me, it's worth it!

The problem we now face is that, while our stars are sharp, the foreground is blurry.  You will need to blend two exposures, foreground and stars, to have a complete image now.

Watch the YouTube video below for a full walk-through on blending 2 exposures together.

 

If you are doing deep space astrophotography, like nebulae or galaxies, there's another process we can try.  It's called photo stacking.  This is where we take multiple photos and stack them to reduce noise.  In each photo there is random noise / grain which obstructs fine detail.  By stacking multiple photos, certain applications are able to find the static detail (galaxy, nebula, stars) and effectively remove the random grain in the photo.  This process works very well when using a star tracker!  I recommend taking at least 20 exposures at night for this to work well. 

Sequator is a free application that can effectively blend exposures together, whether you are shooting at 14mm or 600mm!  This is now my preferred method of photo stacking to reduce noise.  Watch my YouTube tutorial below for a complete walkthrough.

 


Comments

Peter Zelinka
Hi Rob,

I have the same problem! Being 6'3", it's a pain to crouch down and look through the polar scope. However, when using my star tracker with my Feisol 3441-T tripod, it makes things a bit easier. The tripod raises up to about 6' tall, and the star tracker is about at eye level. I still have to crouch down a bit to see through the polar scope.
Rob Walker(non-registered)
Peter, great info and I appreciate all your effort and the great detail you share with us. I tried my SkyTracker for the first time last night and my Meade tripod does not get up high enough making it difficult to crouch down to look through the polar scope. Curious if it is just me? What do you suggest for a tripod?
Bernard Chen(non-registered)
Thank you for this tutorial! I just purchased the Star Adventurer and your site here is the best tutorial out on the web!
Peter Zelinka
Thanks Ross,

Yeah, I normally use ISO 800 when doing my star-tracked exposure, provided I can shoot a successful 4 minute exposure.
Ross B.(non-registered)
Hi Peter, great tutorial, thank you for putting this together. I see that you recommend ISO800 for the foreground shot. Do you also recommend ISO800 for the star-tracking exposure?
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