Guiding With The Sky Watcher Star Adventurer Tracker
Specifications
Mount type: ultra compact equatorial tracking platform
Motor Drive: DC servo
Power Supply: 4 x AA, mini USB (DC 5V external supply)
Payload Capacity: 5kg (not including counterweight)
Tracking Modes: sidereal, lunar, solar, timelapse (2hr, 4hr, 12hr)
This little tutorial only relates to the original Star Adventurer, and not the version 2 that has been released. If and when I upgrade then I’ll write one based on that as well. In the meantime I hope you find this useful.
Polar Alignment
A lot of people when they first start out astro imaging balk at the idea of polar alignment, and that’s simply because it sounds more complicated than it is and they’ve probably read all the horror stories and also how essential it is. Right away there, you’re setting yourself up for more self-induced stress than it needs. I recall when I first started it used to take me upwards of half an hour to do it and I’d get incredibly frustrated. Some of my language would’ve had my little astrohearts covering their ears in embarressment. These days I can have it done inside of 5 minutes. The key thing is patience. Don’t rush it.
The first thing to do is to make sure you’ve done the above three steps, ie levelled, balanced and focused. You should already have the mount (not the telescope unless you’ve used the area around Polaris to focus) pointed in the rough direction of celestial north. If you don’t know where Polaris is, it’s pretty easy to find. My apologies to anyone in the southern hemisphere, but I’m only covering polar alignment in the northern lattitudes. I may well however revisit this at some future point.
What I will say though is that if you can find the Big Dipper, then you can find Polaris, and over time you won’t even need to do the former because you’ll become accustomed to where it is.
Now it’s not as easy as just looking through the polar scope and placing Polaris at the centre of the crosshair. This is because Polaris, like every other star, rotates about a central axis. However, because it’s currently the closest prominent one to that axis of rotation, we refer to it as the North Star, or Celestial North.
Most of us have mobile phones or tablets now so I would recommend downloading an app that will tell you the exact position of Polaris in relation to it’s rotational axis. I personally use Polar Aligner Pro which is available from the Google Play Store. Make sure you have location services enabled on your device and then fire it up. From there select Polaris and then Scope. You should now have a view something similar to the image below.
What you now do is align the mount exactly with Polaris as shown in the app. First off I make sure that I can acually see it in the polar alignment scope and then double check that I’m still level if I’ve had to make any physical movements to the tripod assembly. You also need to set your current lattitude by using the big black knob at the front of the mount. The black handle to the side is to keep friction in the adjustor. Slacken that off when you make your adjustments and retighten it when done. Do NOT overtighten it because that centre screw isn’t that strong and there’s nothing worse than shearing it off, which I’ve done myself. Where I am in the UK I’m at 48 degrees North so that’s where I’m set to.
You then use the bolts at the back of the mount to move left and right. These can take some getting used to, but essentially loosen one off, tighten the other up. You’ll find that you need to crack those allen bolts a very small amount to give yourself some lateral movement.
Depending on the focal length you’re working with you’ll find that this will give you a good polar alignment. But it’s rare that this is completely precise, so you can improve it further by using the Polar Alignment routine in SharpCap which will get you absolutely perfect. I cover this in my Guiding Walkthrough, so I won’t repeat myself here. Suffice to say that using the methods described you can get a pretty perfect polar alignment. And although that walkthrough is written with guiding in mind, the principles of polar alignment, whether using a computerised GoTo mount or a star tracker, remain the same.
Getting On To Your Target
This is where it pays to know the night sky, at least to an extent. Familiarise yourself with the main constellations at your time of year and location. Before computers and the wonders of plate solving, came star hopping. This is NOT as glamourous as it sounds. It’s a pain in the arse, especially when (not “if”) it goes wrong. But you’ll get used to doing it. Know what you want to image, and there’s a lot of great online sources to find out what’s out in your own night sky, find out where it is, and then find out how to get to it.
To move the telescope/camera etc you’ll need to slacken off that RA clutch ring and use the small black knob on the side of the black declination plate it all sits on. Just remember to tighten that RA clutch back up just a touch above finger tight. Too much will strain the gears and too little, or not at all, and it’ll still be in free rotation and won’t track.
You can also manually platesolve if you understand the idea of working with RA and DEC coordinates. You’ll need software that has plate solving capability, such as APT, and you’ll need to know the RA and DEC of your target, but it’s entire possible to get there using that and a combination of pointing in the general direction of where you know your target is.
Guiding With The Star Adventurer
Here I’m going to describe to you both how I actually get on target with the Star Adventurer using the platesolving built into Astro Photography Tools (APT), and also how to guide.
The Star Adventurer has no GoTo ability, so unlike the EQ5 Pro, HEQ5 etc you can’t instruct it by computer to go to whatever it is you’re imaging. This is where it helps to know what is where in the night sky. Even if you don’t, there’s many apps now that can tell you where things are and all you have to do is load the app up and point it at the sky.
The way that I get on target is really quite simple. Once I’m polar aligned, I’ll manually point the imaging train (telescope etc) in the general direction of where I know my target is. It doesn’t matter at this point if you have a finderscope or not as you won’t be using it anyway.
Once there, I’ll fire up APT, go to Live View on the camera tab, and set my exposure to around 5 seconds with the gain I’ll be imaging at, usually 270 and offset 340. I’ll then open up the Objects list under the gear tab and dial in my target, say NGC 6888 for example. Once I’ve done that I’ll then open up PointCraft, again dial in my target, and then run a platesolve.
What I’m looking at is how far out the reported coordinates from the platesolved image are from the target coordinates. Now this is where it pays to know your right ascension from your declination. If you’re using the Star Adventurer this is easy; right ascension is the rotation around the polar scope, whereas declination you achieve by twisting the little black knob on the side of the plate the telescope assembly is sat on. Once you have your platesolved coordinates, hit “Sync.”
Fiddle with your right ascension and declination, and then platesolve again. You’ll notice that your reported coordinates have changed. What you’re attempting to do is have the coordinates in PointCraft match those from the object list. You can do this with any camera that you use through APT, be it a dedicated astronomy camera, or a DSLR. If you’re using a camera in APT, then you can use this method. It’s a lot simpler than star hopping (in my opinion) and DEFINITELY a lot less strain on the back and knees when you’ve hit your 50’s!!
Once your coordinates have more or less matched (I accept no more than one arc minute of accuracy, and if it’s better than that then it’s a bonus), then you know you’re on target and you’re free to image away.
So, onto guiding. Now one of the things with the Star Adventurer is that it has no drive motor in the declination axis, so you’re only going to be guiding in right ascension. Most of us use PHD2 as our guiding software, so I’ll assume you’re doing the same.
If this is your first time using the Star Adventurer and guiding, then you’re going to need to calibrate PHD2 with the mount. Thankfully PHD2 does this for you the first time. If you need to run the Guiding Assistant then make sure you untick “Measure Declination backlash.” Why? Because you have no declination drive to measure in.
Because of the lack of GoTo with the Star Adventurer, you can’t connect to the mount in the manner that you normally would. So, when you need to connect to it, select “On Camera” from the drop-down list. Make sure that your ST4 guide cable is connected from the guidecam to the appropriate port on the body of the Star Adventurer.
From here, you need to tell it to dither in RA only as there’s no declination drive for this mount. Go to the Guide tab, and then Advanced Settings, followed by Global, and then tick the “RA Only” box under Dither Settings as per the image below.
In the algorithms tab, go to the “Dec Guide Mode” and select “Off” from the drop down.
As far as I’m aware, you’re now all set to begin guiding with the Star Adventurer. I have yet to do this myself as I’m having a mechanical issue with mine so I have yet to attempt it. But if you find this useful, or if you think there’s something I’ve missed and need to add, please leave a comment or contact me via my Facebook page.
Update 260920
As of last night, I’ve finally had clear enough skies to have a session guiding with this,and I have to say that I’m pretty impressed. The setup was my usual 72ED and modded Canon 450D. The guiding was carried out using a 9×50 finder and ZWO ASI 120mm.
Setting up was exactly as easy as described above, and with a basic polar alignment and leveling I was managing 3 minute exposures with reasonable stars, despite pretty gusting conditions. I’m happy with those results as a baseline and I’m positive that they will only improve. I’m aware that I’m pushing the weight capacity to the limits with this and expecting a lot from it, but it seems quite happy and stable with it so as a portable guiding solution, it’s just become my go-to (pun intended!)
Update 101020
Last night was the first completely clear night since dinosaurs first roamed the planet, so I decided after a recent bout of illness, even though I still wasn’t feeling at my best, to take advantage of it. Keeping things easy on myself I broke out the portable rig and got onto M45. All I can say is what an incredible night! Not only was I guiding, but I was able to push 5 minute subs using the Star Adventurer and 72ED with the modded 450D and ASI120mm.
Although in the end I decided to keep to 2 minutes, it was amazing to see this setup performing better than my main rig (the EQ5 Pro.) Not only were the stars nice and tight, but across the 2 and a half hours I was imaging, it shifted by maybe 5-10 pixels in total without any dithering. Considering how heavy the setup is in relation to the recommended imaging weight, it performed flawlessly. In all honesty I could’ve probably stayed at 5 minutes and still had to ditch a minimal number. As it was I didn’t have to get rid of a single sub, something I haven’t been able to do for a long time. I’m currently stacking my total M45 data at the moment, which amounts to 5 and a half hours worth, including some from February 2019.
I can honestly say that now I have my head around guiding with this thing, I’m beyond impressed and certainly in a happy place with this setup. I can’t wait to get the ASI178MC on board and try my hand at some proper DSO with good guiding.
Have a great night imaging and for now, clear skies!
AstroHeart UK Photography 