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DIY tropical mount using harmonic motors

DIY tropical mount using harmonic motors

As an astrophotography buff will tell you, you won’t be able to capture the really interesting stuff without spending a lot of money on some decent pieces of equipment. Aside from a telescope, there really is an astonishing amount of complexity, weight, and costs associated with a telescope multiple alone, not to mention that capable of any kind of programmable tracking. [Alan (Jialiang) Zhao] They clearly wanted to raise their level of play, and after experiencing some of the shortcomings of the Sky-Watcher HEQ-5 pro Equatorial mount they decided to go ahead and build an open source base, Alkaid, which hopefully will work a little better for them.

In simple terms, the difficulty of photographing a very distant (or larger but diffuse) object is that the camera sensor needs to spend a significant amount of time averaging the signal, to collect enough lightA piece of fresh water cut from aluminum plate Anything that can be seen through the noise. But this ball of rock we’re sitting on is constantly spinning, so the only solution is to keep track of the thing that’s of interest, to make up. This is referred to as equatorial tracking, and allows compensation for Earth’s rotation during long exposures.

The design of both axles (sorry!) revolves around the use of a NEMA-17 stepper motor with a 27:1 planetary gearbox, driven by a symmetrical reducer gearbox. Harmonic motors (also known as stress wave motors) are very elegant, and operate on the principle of a fixed, but circularly distorted, gear, which transmits torque from the inner surface to the outer, with virtually no backlash. It’s pricey parts, but for a super smooth motion, that’s what you want. The huge output torque they allow, means that [Alan] He was able to build a base for a heavy telescope without any scales. Structurally, everything was made from 10mm thick aluminum plates that had been waterjet cut and then milled to the finish.

On the electronics side, a custom PCB was produced, with a pair of stepper motors based on the TMC2130, controlled by a 4.0 micro. The minimalist design was created with Eagle PCB, and can be found at Alkayd Github Projectalong with frame details and an appropriate copy of OnStep telescope control software. Some 3D-printed side panels hold the electronics in place and the boxes inside, keeping the stand tidy. Kind of industrial look. One important measure of any such mountain, is the gross weight, which [Alan] Reports say it’s around 5.5kg which is less than half that of the HEQ-5, without its scales. Hopefully it’s heavy enough to dampen any vibrations transmitted from the tripod, but testing will prove that one way or the other.

so complicated? Not enough time to build? what about barn door track mount? We have also seen a file Raspberry Pi based star tracker Featured as part of the 2016 Hackaday Award.

thanks for the [Buckarooooo] to get information!



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