Hackaday Podcast Ep2 – Curious Gadgets And The FPGA Brain Trust

In this week’s podcast, editors Elliot Williams and Mike Szczys look back on favorite hacks and articles from the week. Highlights include a deep dive in barn-door telescope trackers, listening in on mains power, the backstory of a supercomputer inventor, and crazy test practices with new jet engine designs. We discuss some of our favorite circuit sculptures, and look at a new textile-based computer and an old server-based one.

This week, a round table of who’s-who in the Open Source FPGA movement discusses what’s next in 2019. David Shah, Clifford Wolf, Piotr Esden-Tempski, and Tim Ansell spoke with Elliot at 35C3.

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DIY Guided Telescope Mount Tracks Like a Barn Door

Astrophotography is an expensive hobby. When assembling even a basic setup consisting of a telescope, camera, guiding equipment and mount, you can easily end up with several thousand dollars worth of gear. To reduce the monetary sting a little, [td0g] has come up with an innovative homebrew mount and guiding solution that could be assembled by almost any dedicated amateur, with the parts cost estimated around $100. The accuracy required to obtain high-quality astrophotographs is quite demanding, so we’re impressed with what he’s been able to achieve on a limited budget.

The inspiration for this design comes from an incredibly simple star tracking device known as a barn-door tracker, or Haig mount. Invented by George Haig in the 1970’s, this mount is essentially nothing more than a hinge aligned with the Earth’s axis of rotation. A threaded rod or screw, turned at a constant rate, is used to slowly open the hinge so that a mounted camera tracks the apparent motion of the heavens. As a result, long exposures can show pinpoint images of stars and sharp details of deep-sky objects, instead of curved star trails. [td0g] adapted this technique to drive a more traditional telescope mount, using barn-door-like drive screws on both the right ascension and declination axes. A pair of NEMA 17 stepper motors drive 4-mm pitch Acme threaded rods through toothed pulleys 3D printed from PETG.

Speaking of 3D-printed parts, this build is a good example of judicious use of the technology: where metal parts are warranted, metal parts are used, and printed plastic is relegated to those places where it can adequately do the job. [td0g] has placed the STL files for the printed parts on Thingiverse in case you want to replicate the drive.

The non-linear relationship between the threaded rod rotation and right ascension drive rate usually limits the length of exposure you can reasonably achieve with a barn-door tracker. To adjust for this, [td0g] created a lookup table in firmware to compensate the drive and allow longer exposures. He mentions that the drive will operate for three hours before it hits the end of the screw’s travel and needs to be reset, but if he can manage three hour exposures, his skies must be much darker than ours!

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Arduino Star Tracker Raises the Bar

Proving that astrophotography doesn’t have to break the bank, [Gerald Gattringer] has recently documented his DIY “barn door” style star tracker which is built almost entirely from scratch. Short of the Arduino and stepper motor, all the components were either made by hand or are standard hardware store finds.

The build starts with three aluminum plates which [Gerald] cut by hand with an angle grinder. He then drilled all the necessary screw holes and a rectangular opening for the threaded rod to pass through. He even used epoxy to mount a nut to the bottom plate which would eventually attach it to the tripod.

The plates were then roughed up and spray painted black so they wouldn’t reflect light. The addition of a couple of screws, nuts, and a standard hinge.

Motion is provided by a 28BYJ-48 stepper which is connected to the drive nut by way of a belt. The spinning nut is used to raise and lower the threaded rod which opens and closes the “door”. To control the motor, [Gerald] is using an Arduino Nano coupled with a ULN2003 Darlington array which live on a routed PCB he made with his school’s Qbot MINImill. While some might say the Arduino is unnecessary for this project, it does make the final calibration of the device much easier.

We’ve covered a number of similar star trackers here on Hackaday, including one that you crank by hand. But the professional looking final result really makes this build stand out.

Build This Barn Door Tracker Today, Take Stunning Shots of the Galaxy Tonight

Think you need some fancy equipment to get stunning shots of the night sky? Surely those long-exposure shots that show the Milky Way in all its glory take expensive telescopes with complicated motor-driven equatorial mounts, right? Guess again – you can slap together this simple barn door tracker for a DSLR for a couple of bucks and by wowing people with your astrophotography prowess tonight.

Those stunning, deeply saturated shots of our galaxy require a way to cancel out the Earth’s movement, lest star trails ruin your long exposure shots. Enter the barn door tracker, a simple device to let you counter the Earth’s rotation. [benrules2]’s version of the tool is ridiculously simple – two boards connected by a hinge. A short length of threaded rod with a large handle passes through a captive nut in the upper board.

A little trig allows you to calculate how much and how often to turn the handle (by hand!) to counter the planet’s 0.25°/minute diurnal rotation. Surprisingly, the long exposure times seem to even out any jostling introduced by handling the rig, but we’d still imagine a light touch and a sturdy tripod would be best. Those of you with less patience might automate this procedure.

It seems a lot to ask of a rig that you could probably throw together in an hour from scrap, but you can’t argue with [benrules2]’s results. His isn’t the only barn door tracker we’ve covered, but it looks like the simplest by far and would be a great project to build with kids.

[via r/DIY]

Astrophotography and Data-Analysis Sense Exoplanets

[David Schneider] was reading about recent discoveries of exoplanets. Simply put these are planets orbiting stars other than the sun. The rigs used by the research scientists include massive telescopes, but the fact that they’re using CCD sensors led [David] to wonder if a version of this could be done on the cheap in the backyard. The answer is yes. By capturing and processing data from a barn door tracker he was able to verify a known exoplanet.

Barn Door trackers are devices used to move a camera to compensate for the turning of the earth. This is necessary when taking images throughout the night, as the stars will not remain “stationary” to the camera’s frame without it. The good news is that they’re simple to build, we’ve seen a few over the years.

Other than having to wait until his part of the earth was pointed in the correct direction (on a clear night) at the same time as an exoplanet transit, [David] was ready to harvest all the data he needed. This part gets interesting really quickly. The camera needed to catch the planet passing in between the earth and the star it revolves around (called a transit). The data to prove this happened is really subtle. To uncover it [David] needed to control the data set for atmospheric changes by referencing several other stars. From there he focused on the data for the transit target and compared points across the entire set of captured images. The result is a dip in brightness that matches the specifications of the original discovery.

[David] explains the entire process in the clip after the break.

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AVR Barn Door Tracker for Astrophotography

zzjBarnDoorTracker

[ZigZagJoe’s] first foray into astrophotography is this impressive AVR barn door tracker, which steps up his night sky photo game without emptying his bank account. If you’ve never heard of astrophotography, you should skim over its Wikipedia page and/or the subreddit. The idea is to capture images otherwise undetectable by the human eye through longer exposures. Unfortunately, the big ball of rock we all inhabit has a tendency to rotate, which means you need to move the camera to keep the night sky framed up.

Most trackers require precision parts and fabrication, which was out of [ZigZagJoe’s] grasp. Instead, he found a solution with the Cloudbait Observatory model, which as best as we can tell looks vaguely similar to the tracker we featured last year. Unlike last year’s build—which uses an ATmega32u4 breakout board— [ZigZagJoe’s] tracker uses an ATTiny85 for the brains, running a pre-configured table that determines step rate against time.

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Building a Barn Door tracker for astronomical photography

That’s a pretty amazing image to catch peering out from your back balcony. The rig used to record such a gem is seen on the right. It’s called a Barn Door tracker and was built by [DCH972]. Details for this build are scattered all over the place, there’s a video (also found below), another album of some of the best images, and plenty of background info in the Reddit thread.

This design is also know as a Haig or Scotch mount. While we’re dropping links all over the place check out the Wikipedia page on the topic. The point of the system is to move the camera in such a way so that the stars appear to hold in the same place even though the earth is moving. There’s an ATmega32u4 breakout board riding on top of the breadboard. It’s doing some pretty heavy math in order to calculate the stepper motor timing. That’s because the mount is like a photo album, hinged at one side and opened on the other by a ball screw. This linear actuation needs to be meshed with the change in angle of the mounting platform, and finally it needs to sync with the movement of the earth. But once a series of images is captured correctly they can be processed into the composite photograph shown above.

If missed that SDR galactic rotation detector from last May you should find it equally compelling.

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