Eclipse 2017: Was Einstein Right?

While most people who make the trek to the path of totality for the Great American Eclipse next week will fix their gazes skyward as the heavenly spectacle unfolds, we suspect many will attempt to post a duck-face selfie with the eclipsed sun in the background. But at least one man will be feverishly tending to an experiment.

On a lonely hilltop in Wyoming, Dr. Don Bruns will be attempting to replicate a famous experiment. If he succeeds, not only will he have pulled off something that’s only been done twice before, he’ll provide yet more evidence that Einstein was right.

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CNC-Telescope With Semi-Nasmyth Mount

[GregO29] had a 10″ GoTo telescope but at 70lbs, it wasn’t really portable. And so he did what any self-respecting CNC enthusiast would do, he put his CNC skills to work to make an 8″ Newtonian reflector, semi-Nasmyth mount telescope of his own design. It also gave him a chance to try out his new Chinese 6040 router/engraver with 800W water-cooled spindle.

What’s all that fancy terminology, you say? “Newtonian reflector” simply means that there’s a large concave mirror at one end that reflects a correspondingly large amount of light from the sky to a smaller mirror which then reflects it toward your eye, preferably along with some means of focusing that light. “Semi-Nasmyth mount” means that the whole thing pivots around the eyepiece so that you can keep your head relatively still (the “semi” is because the eyepiece can also be pivoted, in which case you would have to move your head a bit).

We really like the mechanism he came up with for rotating the telescope in the vertical plane. Look closely at the photo and you’ll see that the telescope is mounted to a pie-shaped piece of wood. The curved outer circumference of that pie-shape has gear teeth on it which he routed out. The mechanism that moves these teeth is a worm screw made from a 1″ spring found at the hardware store that’s on a 3/4″ dowel. Turn the worm screw’s crank and the telescope rotates.

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Cheap USB Control for your Telescope

There’s many complex systems for automatically pointing a telescope at an object in the sky, but most of them are too expensive for the amateur astronomer. [Kevin]’s Arduino ST4 interface lets you connect your PC to a reasonably priced motorized telescope mount, without ripping it apart.

The ST4 port is a very basic interface. There’s one pin per direction that the mount can move, and a common pin. This port can be added to just about any motorized mount with some modification to the controller. To connect to an Arduino, a TLP521-4 quad optoisolator is used. This keeps the Arduino and PC fully isolated from the motor circuits. but lets the Arduino take control of the mount.

With the hardware in place, [Kevin] cranked out some software which is available on Google Code. A simple Arduino sketch provides the USB interface, and a custom driver allows the ASCOM Platform to control the mount. Since many astronomy software tools support ASCOM, this allows the mount to be controlled by existing software.

With the interface in place, the mount can be used to find objects (GOTO) and automatically follow them with high accuracy (autoguiding). You can watch the telescope move on its own after the break.

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THP Entry: Making Amateur Astronomy Easy

explrad With the advent of electronics in everything, amateur astronomy has never been easier. Telescope mounts that point in the direction of any astronomical object automatically have been around for decades, and the Telrad – a device that paints 0.5, 2, and 4 degree diameter circles in your finder scope’s field of view are available if you’re just too cool for letting a robot do your job. [Christoph]’s explorad takes the concept of a Telrad and adds a somewhat more electronic twist: it still displays the field of view circles, but adds highlighting of interesting astronomical objects from a custom telescope mount, a huge database, and a few sensors.

By far the biggest challenge to any homebrew finder of astronomical objects is figuring out where the observer is. Not only does [Cristoph] need to take into account the location on Earth (GPS helps with that), but also where North is (electronic compass), where the telescope is pointing (optical encoders on a two axis mount), but also the universal time and current sidereal time. Living on a rotating planet that orbits a sun makes for a lot of code.

The current progress on the star finder to beat all star finders is a bit of code that draws the ‘telrad circles’ and displays placeholders for each patch of sky with a small triangle. Tilting the device or turning the azimuth pot moves these triangles and loads new ones on the fly. Now the name of the game is a sky object database for all the astronomical objects [Cristoph] wants to view.