This week’s selection is the incredible ABSDBS telescope project by Aleksej Cherenkov.
St. Petersburg-based Cherenkov is an amateur astronomer, and, like many amateur astronomers, is prone to making and modifying observation equipment. This Thingiverse project is literally to build an operational eight-inch Dobsonian telescope.
A Dobsonian telescope configuration refers to the mounting mechanism, which allows the optical tube to be pointed and held steady. It’s basically a tilting axis mounted on a rotatable turntable, and is able to point to any location in the sky.
The actual telescope portion of the project is essentially a Newtonian design, in which light hits a large mirror at the bottom, where it reflects it on a smaller secondary mirror near the top. This secondary mirror redirects the light out the side, where it can be focused with a moveable eyepiece.
This project will produce a truly usable telescope of this design. There are a large number of printable parts required - seventy-nine by my count, as well as a number of non-3D printed items such as aluminum tubes, springs, bearings, spider vanes and a great many nuts and bolts.
Printing of these parts is possible on any desktop 3D printer with at least a 200 x 200mm print surface, so this should include almost every machine. However, you’ll need a considerable amount of filament and a great deal of time to finalize printing of these numerous parts.
It will also require quite a bit of time to assemble the telescope. How difficult will this be? Not so much, but it will take some time as you can see in this assembly video:
The ABSDBS project will require you to acquire a separate main parabolic mirror. These are purchasable from various astronomical sources, but it’s also possible to make them yourself, if you know how. It’s a long process, but you can buy an astronomical glass blank and slowly grind it down into the correct shape, after which a mirror coating is applied.
One key element that’s not included in the ABSDBS project is the focuser. This is the mechanism that precisely moves the eyepiece back and forth to find the focal point, and is obviously critical for correct telescope operation. Fortunately, another Thingiverse contributor, Brazilian Marcelo Bastos, has provided a suitable focuser design that’s also 3D printable.
After some time and effort you will produce a perfectly usable optical telescope. Note that this design will not automatically track your observation target as the Earth rotates - this is a manually operated design that will require you to periodically push the scope along to keep tracking. For automatic tracking, quite a bit more engineering is required, as well as some precision motors.
This project is freely available for download from Thingiverse, but you should consider your ability to get through a big effort to print and assemble all the required components before you start.