Greetings, friends of the night sky. Some time ago I reported here about my last self-made astro tracker. I made almost the entire device on the 3D printer, including the gears for the transmission. Unfortunately, the part is far too imprecise and therefore a case for the scrap heap. That's not particularly annoying. I didn't have to buy many parts, I can remove the electronics and ball bearings and use them for new projects. And I've learnt something again. An aspect that should not be underestimated.

The construction of the new tracker is not that exciting. It is based on a Nema17 stepper motor with a flange-mounted planetary gearbox with a reduction ratio of 264:1. The camera is attached to the axis of the gearbox and an Arduino controls the steps.

I wanted to build the machine as small as possible, but I still wanted it to be sufficiently stable. I decided to place the motor with the gearbox in the housing without any additional mountings. The motor sits in the housing in all directions without any significant play. The connection between the gearbox and the mount for the camera is held without play by two ball bearings.

The electronics are housed above the motor. A board including a driver to control the motor, a step-up module that converts 5V to 12V DC and the Arduino. The machine is powered via a USB C socket, which I built into the housing.

I have also installed a six-pole, three-stage slide switch to operate the tracker at half speed. My idea behind this is that I can expose for longer without the stars painting lines in the picture, but also without the foreground being blurred by the rotation of the tracker. Whether this idea works remains to be seen. I haven't tested it yet because the moon is shining brightly all night at the moment.

First I set up a stable tripod, in this case an Innorel NT404C. With the rickety travelling tripod for €39.90 it won't be possible to get a tracking shot, in the worst case the whole thing will just tip over.

I then align the mount for the tripod head with the built-in levelling base. To do this, I attach a spirit level to it. The housing for this also comes from the 3D printer. As far as I know, you can't buy something like this.

I then mounted a modified 2-way panhead on the tripod. I screwed the panorama plate, which actually sits on top of the panhead, under the panhead. I screwed on an Arca Swiss clamp at the top. This allows me to adjust the elevation angle and direction separately and quite precisely.

A holder for my mobile phone then goes into the Arca clamp. Unfortunately, it has disappeared into some black hole. That's why it's missing in the following picture. As you have already guessed, I also made the holder on the 3D printer. I then use the "PolarAligner Pro" app to align the inclinometer precisely to the earth's axis. You could also check this with a polar scope. I didn't do this in daylight.

If the alignment is correct, the tracker is mounted on the panhead. I attach a V mount to the top of the panhead so that the underside of the tripod head is more or less level.

Then a low-profile ball head and the camera are attached.

If I were actually photographing the stars, I would now align the camera to the desired image section and focus. Once this is done, the heating cuff is attached to the lens to prevent the front lens from fogging up. The heating cuff and tracker are then connected to a USB power bank.

Finally, the LRTimelapse Timer is attached to the hot shoe to control the camera. And that's it. Sounds complicated? It is. Good alignment in particular is difficult and often leads to unusable images. But somehow that's exactly what makes it so appealing.

I only built the tracker because I already had the motor with the gearbox. This design is not the best. The weight is high, over 850 g. The mount for the camera is not particularly stable. Ultimately, the camera is held in place by four M3 screws, which sit in four small melt-in sleeves. On the other hand, the tracker runs very precisely. After 11 hours and 58 minutes, the tracker had rotated by exactly 180°. The centre of gravity is relatively flat over the tripod shoulder. Even strong gusts of wind will not move the camera. I'm already looking forward to the first pictures I take with the tracker and I'm even more excited to see how long it will last. Until then, good light at all times.