Stars Looking A Bit Dim? Throw Some Math At Them.

As the cost of high-resolution images sensors gets lower, and the availability of small and cheap single board computers skyrockets, we are starting to see more astrophotography projects than ever before. When you can put a $5 Raspberry Pi Zero and a decent webcam outside in a box to take autonomous pictures of the sky all night, why not give it a shot? But in doing so, many hackers are recognizing a fact well-known to traditional telescope jockeys: seeing a few stars is easy, seeing a lot of stars is another story entirely.

The problem is that stars are fairly dim; a problem compounded by the light pollution you get unless you’re out in a rural area. You can’t just brighten up the images either, as that only increases the noise in the image. A programmer always in search of a challenge, [Benedikt Bitterli] decided to take a shot at using software to improve astrophotography images. He documented the entire process, failures and all, on his blog for anyone else who might be curious about what it really takes to create the incredible images of the night sky we see in textbooks.

In principle it’s simple: just take a lot of pictures of the sky, stack them on top of each other, and identify which points of light are stars and which ones are noise artifacts. But of course the execution is considerably more difficult. For one thing, unless the camera was on a mount that was automatically tracking the sky, the stars will have slightly moved in each image. To help with this process, [Benedikt] used a navigational trick that humanity has relied on for millennia: mapping constellations. By comparing groupings of stars in each image, his software is able to accurately overlay each image.

But that’s only one part of the equation. In his post, [Benedikt] goes over the incredible amount of math that goes into identifying individual stars in the sea of noise you get when a digital image sensor looks into the black. You certainly don’t need to understand all the math to appreciate the final results, but it’s a fascinating read for those with an interest in computer vision concepts.

This kind of software is precisely what you want to pair with your 3D printed star tracker, or even better a Raspberry Pi sky monitoring station.

[Thanks to Helio Machado for the tip.]

3D Printed Clockwork Star Tracker

Astrophotography is one of those things you naturally assume must be pretty difficult; surely something so awesome requires years of practice and specialized equipment which costs as much as your car. You shake your fist at the sky (since you have given up on taking pictures of it), and move on with your life. Another experience you’ll miss out on.

But in reality, dramatic results don’t necessarily require sticker shock. We’ve covered cheap DIY star trackers before on Hackaday, but this design posted on Thingiverse by [Tinfoil_Haberdashery] is perhaps the easiest we’ve ever seen. It keeps things simple by using a cheap 24 hour clock movement to rotate a GoPro as the Earth spins. The result is a time-lapse where the stars appear to be stationary while the horizon rotates.

Using a 24 hour clock movement is an absolutely brilliant way to synchronize the camera with the Earth’s rotation without the hoops one usually has to jump through. Sure you could do with a microcontroller, a stepper motor, and some math. But a clock is a device that’s essentially been designed from the ground up for keeping track of the planet’s rotation, so why not use it?

If there’s a downside to the clock movement, it’s the fact that it doesn’t have much torque. It was intended to move an hour hand, not your camera, so it doesn’t take much to stall out. The GoPro (and other “action” cameras) should be light enough that it’s not a big deal; but don’t expect to mount your DSLR up to one. Even in the video after the break, it looks like the clock may skip a few steps on the way down as the weight of the camera starts pushing on the gears.

If you want something with a bit more muscle, we’ve recently covered a very slick Arduino powered “barn door” star tracker. But there’re simpler options if you’re looking to get some shots tonight.

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Pi Zero Gives Telescope Hands Free Focus

It seems like [Jason Bowling] never gets tired of finding new ways to combine the Raspberry Pi with his love of the cosmos. This time he’s come up with a very straightforward way of focusing his Celestron 127SLT with everyone’s favorite Linux SBC. He found the focus mechanism on the scope to be a bit fiddly, and operating it by hand was becoming a chore. With the Pi Zero and a stepper motor, he’s now able to focus the telescope with more accuracy and repeatability than clumsy human fingers will be able to replicate.

On this particular type of telescope, the focus knob is a small knob on the back of the scope (rather than on the eyepiece), which just so happens to be the perfect size to slide a 15mm bore pulley over. With a pulley on the focus knob, he just needed to mount a stepper motor with matching toothed pulley next to it and find a small enough belt to link them together. Through the magic of Amazon and McMaster-Carr he was able to find all the parts without having to make anything himself, beyond the bent piece of aluminum he’s using as a stepper mount.

To control the stepper, [Jason] is using an EasyDriver connected up to the Pi’s GPIO, which along with a 5V regulator (which appears to be a UBEC from the RC world) is held in a tidy weather proof box mounted to the telescope’s tripod. The regulator is necessary because the whole setup is powered by a 12V portable “jump start” battery pack for portability. Handy when you’re stargazing in the middle of a field somewhere.

[Jason] promises a future blog post where he details how he used Flask to create a web-based control for the hardware, which we’ll be keeping an eye out for. In the meantime, he reports that his automated focus system is working perfectly and keeps the image stable in the eyepiece even while moving (something he was never able to do by hand).

Last year this same scope had a Raspberry Pi camera mounted to it to deliver some very impressive pictures without breaking the bank. We’re interested in seeing how [Jason] ties these systems together going forward.

Casein, Cello, Carrotinet, and Copper Oxide, Science Grab Bag

One of our favorite turnips, oops, citizen scientists [The Thought Emporium], has released his second Grab Bag video which can also be seen after the break. [The Thought Emporium] dips into a lot of different disciplines as most of us are prone to do. Maybe one of his passions will get your creative juices flowing and inspire your next project. Or maybe it will convince some clever folks to take better notes so they can share with the rest of the world.

Have you ever read a recipe and thought, “What if I did the complete opposite?” In chemistry lab books that’s frowned upon but it worked for the Reverse Crystal Garden. Casein proteins make cheese, glue, paint, and more so [The Thought Emporium] gave us a great resource for making our own and demonstrated a flexible conductive gel made from that resource. Since high school, [The Thought Emporium] has learned considerably more about acoustics and style as evidence by his updated cello. Maybe pulling old projects out of the closet and giving them the benefit of experience could revitalize some of our forgotten endeavors.

If any of these subjects whet your whistle, consider growing gorgeous metal crystals, mixing up some conductive paint or learning the magnetic cello. Remember to keep your lab journal tidy and share on Hackday.io.

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Astro Cat: Raspberry Pi Telescope Controller

When somebody tackles an engineering problem, there are two possible paths: they can throw together a quick and dirty fix that fits their needs (the classic “hack”, as it were), or they can go the extra mile to develop a well documented solution that helps the community as a whole. We cover it all here at Hackaday, but we’ve certainly got a soft spot for the latter approach, even if some may feel it falls into the dreaded territory of “Not A Hack”.

When [Gary Preston] wanted to control his telescope and astrophotography hardware, he took the second path in a big way. Over the course of several posts on his blog, [Gary] walks us though the creation of his open source Raspberry Pi add-on board that controls a laundry list of sensors and optical gear. Just don’t call it a HAT, while it may look the part, [Gary] is very specific that it does not officially meet the HAT specifications put out by the Raspberry Pi Foundation.

Even if you aren’t terribly interested in peering into the infinite void above, the extremely detailed write-up [Gary] has done contains tons of multidisciplinary information that you may find useful. From showing how to modify the Pi’s boot configuration to enable true hardware UART (by default, the Pi 3 ties it up with Bluetooth) and level shifting it with a ST3232 to a breakdown of the mistakes he made in his PCB layout, there’s plenty to learn.

Astro CAT is a completely open source project, with the hardware side released under the CERN Open Hardware License v1.2, and the INDI driver component is available under the GPL v3.

If this looks a bit daunting for your first stab at astrophotography with the Raspberry Pi, fear not. We’ve covered builds which can get you up and running no matter what your budget or experience level is.

Weatherproof Pi Looks Up So You Don’t Have To

Skywatching is a fascinating hobby, but does have the rather large drawback of needing to be outside staring at the sky for extended periods of time. Then there’s the weather to contend with, even if you’ve got yourself a nice blanket and it isn’t miserably cold, there might be nothing to see if cloud cover or light pollution is blocking your view.

Highly scientific testing procedure.

To address these issues, [Jason Bowling] decided to put a Raspberry Pi in a weatherproof enclosure and use it as a low-cost sky monitoring device. His setup uses the No-IR camera coupled with a cheap wide-angle lens designed for use with smartphone camera. The whole setup is protected from the elements by a clear acrylic dome intended for a security camera, and a generous helping of gasket material. Some experiments convinced [Jason] to add a light pollution filter to the mix, which helped improve image contrast in his less than ideal viewing area.

The software side is fairly straightforward: 10 second exposures are taken all night long, which can then be stitched together with ffmpeg into a timelapse video. [Jason] was concerned that the constant writing of images to the Pi’s SD card would cause a premature failure, so he set it up to write to a server in the house over SSHFS. Adding a USB flash drive would have accomplished the same thing, but as he wanted to do the image processing on a more powerful machine anyway this saved the trouble of having to retrieve the storage device every morning.

This isn’t the first time [Jason] has used a Pi to peer up into the heavens, and while his previous attempts might not be up to par with commercial offerings, they definitely are very impressive considering the cost of the hardware.

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Hackaday Links: 👻 🎃 Spooky Edition, 2017

A few links posts ago, we wrote something about a company selling huge LED panels on eBay, ten panels for $50. Those panels are gone now, but a few lucky hackers got their hands on some cool hardware. Now there’s a project to reverse engineer these Barco NX-4 LED panels. Who’s going to be the first to figure out how to drive these things? Doesn’t matter — it’s a group project and we’re all made richer by the contributions of others.

Prague is getting a new hackerspace.

A year and a half ago, a $79 3D printer popped up on Kickstarter. I said I would eat a hat if it shipped by next year. Seeing as how it’s basically November, and they’re not selling a $79 printer anymore — it’s $99 — this might go down as one of my rare defeats, with an asterisk, of course. I’m going to go source some very large fruit roll-ups and do this at Supercon. Thanks, [Larry].

Speaking of bets, this week Amazon introduced the most idiotic thing ever invented. It’s called Amazon Key. It’s an electronic lock (dumb), connected to the Internet (dumber), so you let strangers into your house to deliver packages (dumbest). CCC is in a few months, so I don’t know if Amazon Key will be hacked by then, but I’m pretty confident this will be broken by March.

The Lulzbot Taz is one of the best printers on the market, and it is exceptionally Open Source. The Taz is also a great printer for low-volume production. It was only a matter of time until someone built this. The Twoolhead is a parallel extruder for the Taz 6. Instead of one extruder and nozzle, it’s two, and instead of printing one object at a time, it prints two. Of course it limits the build volume of the printer, but if you need smaller parts faster, this is the way to go.

Hey, did you hear? Hackaday is having a conference the weekend after next. This year, we’re opening up the doors a day early and having a party at the Evil Overlord’s offices. Tickets are free for Supercon attendees, so register here.

At CES this year, we caught wind of one of the coolest advances in backyard astronomy in decades. The eVscope is ‘astrophotography in the eyepiece’, and it’s basically a CCD, a ton of magic image processing, and a small display, all mounted inside a telescope. Point the scope at a nebula, and instead of seeing a blurry smudge, you’ll see tendrils and filaments of interstellar gas in almost real-time. Now the eVscope is on Kickstarter. It’s a 4.5 inch almost-Newtonian (the eyepiece is decoupled from the light path, so I don’t even know how telescope nomenclature works in this case), an OLED display, and a 10-hour battery life.

Is the fidget spinner fad over? Oh, we hope not. A technology is only perfected after it has been made obsolete. Case in point? We can play phonographs with lasers. The internal combustion engine will be obsolete in automobiles in twenty years, but track times will continue going down for forty. Fidget spinners may be dead, but now you can program them with JavaScript. What a time to be alive!

Audio tomphoolery even an idiot tech blogger can see through! I received a press kit for a USB DAC this week that included the line, “…low drop out voltage regulators running at 3.3 V, meaning the 5 V USB limit is well preserved.” Yes, because you’re running your system at 3.3 V, you won’t draw too much current from a USB port. That’s how it works, right?

[Peter Sripol] is building an ultralight in his basement. The last few weeks of his YouTube channel have been the must-watch videos of the season. He’s glassed the wings, installed all the hardware (correctly), and now he has the motors and props mounted. This is an electric ultralight, so he’s using a pair of ‘150 cc’ motors from HobbyKing. No, that’s not displacement, it’s just a replacement for a 150 cc gas engine. On a few YouTube Live streams, [Peter] did what was effectively a high-speed taxi test that got out of hand. It flew. Doing that at night was probably not the best idea, but we’re looking forward to the videos of the flight tests.