Building a mini observatory

There is a point in astrophotography where the telescope is no longer the hard part.

That sounds strange at first, because most of us spend years thinking the next telescope, the next mount, the next camera, or the next filter will solve the problem. Sometimes it does. More often, it just moves the problem to another part of the chain.

After enough nights under the sky, you start to realize that the biggest obstacle is often not optics, tracking, guiding, or processing. It is friction.

Friction is carrying gear outside after dinner when you are already tired. It is leveling the tripod, running cables, balancing a mount, polar aligning, checking focus, waiting for the first plate solve, and hoping the clouds hold off long enough to justify the effort. It is getting everything working just as the sky starts to soften with moisture. It is tearing down a perfectly good setup at two in the morning because rain might come before breakfast.

I love this hobby. I have been in and around astronomy for most of my life, and I still get pulled in by the simple fact that a small instrument in a backyard can collect light that has been traveling for longer than human history. But I also know how ordinary the work can feel. Astrophotography is full of wonder, but it is also full of extension cords, lost thumb screws, USB errors, dew heaters, firmware updates, and nights where the best thing you capture is a lesson.

That is why the idea of a home observatory makes so much sense.

Not necessarily a large dome in the countryside. Not necessarily a concrete pier, a building permit, and a budget that makes your spouse stop talking for a week. I am talking about something smaller and more practical. A micro observatory. A compact, automated shelter for modern gear that can live where you live.

As telescopes, cameras, mounts, and control systems become more portable and more capable, the idea of building a small observatory at home starts to look less like an indulgence and more like common sense. We already have lightweight strain wave mounts, cooled cameras, small refractors with excellent optics, plate solving, autofocus, remote desktop control, sequencing software, smart weather stations, and home automation systems. In many cases, the equipment is ready before the owner is.

The chase for full automation has been part of astrophotography for a long time. A lot of us dream about a system that waits patiently under cover, opens when the sky is clear, runs a sequence, closes itself, and lets us collect data without spending the whole evening staging equipment. Commercial remote observatories can do that, but they come with real costs. Pier rental is not cheap. Service can require patience. If the weather is poor at that site, you may still be shut down. And if something small goes wrong, your telescope may be hundreds or thousands of miles away.

But remote does not have to mean far away.

Remote can mean your backyard. Your garage roof. A corner of your patio. A place close enough to touch, but automated enough to use from inside the house. If it is done correctly, a backyard setup can behave like a remote observatory even if it is only fifty feet from your desk.

That matters because most of us do not live under perfect skies. Bortle 1 skies are disappearing, and even people who live under Bortle 2 skies today may not have that forever. Light pollution is not someone else’s problem. It is becoming part of the operating environment for modern amateur astronomy. We can complain about it, and sometimes we should, but we also have to adapt.

The good news is that today’s equipment gives us more ways to adapt than we have ever had. Narrowband filters, sensitive sensors, smart calibration, better software, and repeatable automation all help us make productive use of skies that are not ideal. The trick is to remove enough setup friction that we actually use those tools regularly.

That is where Engelbert Vollmer’s micro observatory becomes interesting.

I recently had a conversation with Engelbert about how he built a 3D printed clamshell observatory, why he wanted one in the first place, and what he learned from the project. His answers were practical, honest, and refreshingly grounded. He did not describe a fantasy product or a one click shortcut. He described a careful build by someone who understands both the appeal and the work.

Meet Engelbert Vollmer

Engelbert Vollmer lives in a small city near Heidelberg, Germany. His background is not casual. He studied physics and astronomy and earned a doctorate in space research before moving into management consulting, where he spent much of his professional life before retiring.

His interest in astronomy started early, in a way that will sound familiar to many amateur astronomers. As he told me, “When I was about 10 years old, I was given a paperback book as a gift, ‘Which Star Is That?’ That naturally sparked my imagination.”

That spark was helped along by his uncle, who encouraged his interest, and later by a small refractor he received as a Christmas gift. It was enough to show him the Moon, the Andromeda Galaxy, the Orion Nebula, and a few star clusters. That is often all it takes. A small telescope does not need to be perfect. It just has to show enough truth to make a person want more.

As a teenager, Engelbert and his brother went further. They ground small mirrors and built simple reflector telescopes. That detail says a lot. Some people enter astronomy through observing. Some through photography. Some through gear. Engelbert seems to have entered through all of it at once.

When I asked what kind of observing or imaging he enjoys most today, he gave the kind of answer that comes from someone who has spent enough years at the eyepiece to know what matters.

“My eyesight has deteriorated somewhat over the years, so I don’t observe much anymore; instead, I mostly take photographs. But I also particularly love standing at the telescope, enjoying the sky and the magic of the night, and taking pleasure in equipment that works.”

That last phrase stuck with me. Taking pleasure in equipment that works.

Astrophotographers understand that sentence in their bones. We are not looking for equipment for its own sake, although some of us are guilty of acting like it. We are looking for the quiet satisfaction of a system doing what we built it to do. A mount that tracks. A camera that cools. A focuser that lands where it should. A sequence that starts and finishes without drama. There is a real kind of peace in that.

A Lifetime Of Looking Up And Building Things

Engelbert describes himself as an astrophotographer at heart, but also as someone who needs to build with his hands and put those things to use. That combination matters because his observatory is not just an astronomy project. It is a maker project, an automation project, and a practical response to a common problem.

His equipment path also sounds like a familiar modern journey. When he found more spare time in the mid 2010s, he started with a GSO Newtonian at 1000 mm focal length and a QHY10 camera on an HEQ5 Pro mount. Later he moved to a Celestron 8 inch EdgeHD and a ZWO ASI183MC Pro. Over time, he added a Sharpstar 150 mm f 2.8, a ZWO ASI2600MC, an electronic filter wheel, an electronic focuser, ASIAir, an AM5 mount, and the expected collection of accessories that seems to multiply on its own.

Today he mainly uses the Sharpstar or the C8 with the ASI2600 on the HEQ5. In the mini dome, he uses an Askar SQA55 on an AM5 with the ASI183.

His memorable experiences are a good reminder that even highly technical astrophotographers usually begin with simple visual impressions. He remembers seeing Saturn and its rings for the first time as a teenager.

“It glowed like a jewel in the dark,” he said.

He also remembers Omega Centauri, lunar eclipses, solar eclipses in the United States in 2017 and 2024, northern lights in Norway, meteors, and the challenge of imaging the gravitational lens known as the Andromeda Parachute.

That range is important. Astronomy is not one thing. It is the Moon in a small refractor, a total solar eclipse, a faint quasar, a radio minded builder making circuits, and a retired physicist trying to make a little dome open and close correctly on command.

Why A Mini Observatory Made Sense

Engelbert’s local conditions are not the kind that make astrophotographers jealous. He lives near a major city, around Bortle 6 to Bortle 7, and the weather is often cloudy.

“Clear, good nights are rare,” he told me. “And it feels like there are fewer of them every year.”

That sentence could have come from almost any amateur astronomer I know. The details change from one place to another, but the pattern is the same. Light pollution grows. Weather feels less predictable. Free time becomes harder to protect. The sky does not care about your schedule.

For years, Engelbert set up his telescopes in the garden in the evening and took them down again in the morning. It worked, but it became exhausting. His garden had limited sky because of trees, but the top of the garage offered a wider field of view. A traditional larger observatory would not work there, so he started thinking smaller.

“Then, at some point, I got the idea of wanting a small observatory where I could at least use my Samyang 135mm with the ASI183MC,” he said. “And the observatory wasn’t supposed to be just anything. It had to look like a real observatory. Unfortunately, I couldn’t find anything suitable on the market. That’s when I got the idea to build, or rather, 3D print one myself.”

That is the heart of this project. It was not built because a 3D printed observatory is novel. It was built because there was a specific need, and the market did not offer a good answer.

That is usually where good amateur astronomy projects come from. Not from chasing novelty, but from solving a real problem in a specific backyard.

A Real Observatory In Small Form

There is something appealing about Engelbert’s insistence that the dome look like a real observatory. That may sound cosmetic, but I do not think it is. Instruments matter to us partly because they represent intent. A telescope on a tripod is temporary. A dome says the sky has a permanent place in your life, even if the dome is small enough to sit on a garage roof.

His first mini observatory was designed to handle a wide range of use cases. He admits it may have been overengineered, but it worked. It could only hold a lens with a maximum focal length of about 110 mm when paired with the ASI183MC. For the second version, he wanted to fit something closer to 300 mm focal length, which meant building larger.

He chose another clamshell design, but improved the details based on what he had learned. He also decided that the second observatory would run under Windows with N.I.N.A. instead of ASIAir.

The clamshell approach was not accidental. A traditional observatory dome with a single opening would have made installation and maintenance difficult because the telescope needed to be accessed from above. Engelbert explained it plainly.

“So, the dome had to be designed to open almost completely. That left only the clamshell design.”

That is a good example of engineering by constraint. The site, the equipment, and the maintenance needs decide the design. Not the other way around.

 

The Design Process

Engelbert used Fusion 360 to design the observatory. He chose it because it is free for personal use and capable of complex designs. He is also honest about the limits of his own project files.

“Since I’m not exactly an expert in Fusion 360 and because I designed the observatory for myself, my Fusion 360 project is a bit disorganized and not well documented,” he said.

That kind of honesty matters. Many build articles make projects look cleaner in hindsight than they were in real life. Engelbert is clear that his design is not something an average person can simply open and modify without experience. Some later parts were built on earlier parts, and changing the older designs could affect newer ones. His view is that it may be easier for someone to start a fresh design inspired by his work than to directly modify his files.

The observatory includes roughly 70 to 80 printed parts. The main structure includes a base ring, an intermediate ring, and four movable half shells that open and close the dome. Since these could not be printed as single pieces, he used slicer software to divide the rings and shell sections into smaller printable parts.

The base and intermediate rings were cut into eight sections. Each curved half shell was cut into eight or ten sections. The rings were joined with printed connectors that hold the pieces together like clamps. For the curved shells, he used multiple overlapping layers, with cuts placed at different positions so the parts could be glued and screwed together for strength.

That is a useful lesson for anyone thinking about large format 3D printing. Strength does not come only from material choice. It comes from how the pieces are divided, aligned, overlapped, fastened, and protected.

Printing The Dome

For the printer, Engelbert chose a Creality K1 Max. The reason was simple. It offered a 30 cm by 30 cm by 30 cm build volume, which allowed him to print reasonably sized parts, and it had enough speed to make the project practical.

He estimated the print time at about 15 days of pure printing. In practice, it took about four weeks to finish all the parts.

The material was PETG. Engelbert had used PETG before on outdoor weather station parts, and those parts had held up for years without obvious wear. For added protection, he painted the entire dome with white acrylic paint.

The total filament use was about 12 kilograms. He estimated the filament cost at around 250 dollars, with another 150 dollars for screws, motors, cables, buttons, connectors, an Arduino, and other small parts. Assuming the builder already has the tools and can do the work, he estimated the total cost at around 400 dollars.

That number will get attention, and it should, but it needs to be understood correctly. This is not a 400 dollar commercial product. It is a 400 dollar materials estimate for a capable builder who already owns the printer and tools, has the patience to print for weeks, and can handle assembly, wiring, programming, and troubleshooting.

That does not make the result less impressive. It makes it more honest.

Large prints did create some issues. After hours of printing, some of the curved parts warped slightly, leaving small gaps of 1 to 2 mm during assembly. Engelbert filled those with two part filler and sanded them smooth before painting.

Again, that is the real story of do it yourself astronomy. Not perfection, but correction.

Weather Protection And Durability

A small observatory has one job before all others. It has to protect the equipment.

Engelbert designed the dome to be waterproof, with half shells overlapping by about 5 cm. Screws in the shells are sealed with silicone. The dome is mounted on a waterproof hardwood panel anchored into paving stones, so wind has not been a problem.

Still, he does not pretend it is invincible.

“Nevertheless, during prolonged periods of bad weather or heavy rain, I cover the observatory with a cover designed specifically for this purpose,” he said.

That is the kind of answer I trust. Not everything has to be built like a professional mountaintop enclosure. It has to be built well enough for its environment, and the owner has to understand its limits.

So far, light rain has not caused damage. Heavy rain is handled with the cover. The temperature inside the dome follows the outside temperature quickly, ranging from about 40 degrees Celsius in summer to minus 10 degrees Celsius in winter. Humidity can reach 90 percent.

Engelbert experimented with homemade heaters using Peltier elements and PTC heating elements, but neither solution was powerful enough, so he removed them. Even so, he reports no problems after one year of operation.

For harsher climates, he would increase the overlap of the half shells from 5 cm to perhaps 10 cm and improve the drip edge to stop water from creeping along the shell into the interior.

Dew control is handled in a practical way. The inside of the dome remains dry even when the area around it is soaked with humidity. The electronics, dew bands, and mini PC provide some internal heat. The telescope and guide scope use heating strips controlled by a self regulating dew heater that adjusts power based on dew point and temperature changes. After an imaging session ends, the dome closes, but the electronics and heaters remain on for several more hours.

This is exactly the sort of detail that separates a display project from a working observatory.

The Automation That Makes It Useful

A shelter is helpful. An automated shelter is better.

Engelbert originally considered using scale model winch motors because they looked good and could lift each four kilogram half shell. But they were not self locking. When power was off, the shell weight could cause the motors to rotate backward and the dome to open.

That is the kind of problem that only sounds small until your telescope is sitting outside in weather.

He replaced them with small 12 volt DC motors with worm gear drives. These are self locking by design. Each motor turns a drum that winds a thin wire rope. The rope runs over a pulley along the outside of the rings and attaches to the lower end of the half shell. The motor pulls the shell upward to close the dome and releases it to open.

An Arduino Uno controls the motors through an L298N module. The dome can be operated by button or through an ASCOM interface. The motors can run independently in both directions. Microswitches report the end positions of each half shell and stop the motors. As a backup, the motors also stop automatically two seconds after their expected runtime.

That backup matters. Automation should never depend on a single point of trust. A limit switch can fail. A lever can bend. A cable can snag. A responsible system expects ordinary things to go wrong.

The observatory also includes environmental monitoring. A DHT22 sensor measures temperature and humidity. A temperature dependent resistor attached to the telescope tracks temperature changes there. A microprocessor uses PWM modules to regulate the dew heater strips and measures their current draw with an ACS712 module. Those readings are displayed on a dedicated website.

Outside the dome, Engelbert built a small weather station that measures temperature, humidity, rainfall, infrared temperature, and sky brightness. The data goes to Home Assistant and an MQTT server that acts as a safety monitor during operation.

For imaging control, he uses a mini PC running Windows 11 Professional and N.I.N.A., the open source imaging software created and maintained by Stefan Berg and contributors. The system can be controlled over Remote Desktop and accessed through the local network or by VPN.

That is a proper modern backyard observatory workflow. Local equipment. Remote control. Weather awareness. Imaging automation. Human oversight when needed.

What Fits Inside

The current equipment inside the dome is an Askar SQA55 telescope with a 264 mm focal length on a ZWO AM5 mount, paired with an ASI183MC Pro camera, rotator, filter wheel, focuser, and an ASI120MM guide camera with a 130 mm f 4 guide scope. The total payload is about six kilograms.

The AM5 matters because the strain wave design does not require a counterweight in this configuration. That helps keep the system compact and reduces the space needed inside the dome.

Engelbert designed the system so the dome can close regardless of telescope position. For automation, that is not a small feature. It means the observatory is less dependent on a perfect park state before closing.

The total length of his system with dew shield extended is about 460 mm, and he considers that close to the outer limit. What fits depends not just on focal length, but on the diameter of the telescope and camera, how the guide scope and focuser are mounted, where the mount pivot points sit relative to the center of the dome, and how large the unobstructed aperture is.

Could the design be scaled up for a small refractor in the 60 mm to 80 mm range, or even a compact SCT? Engelbert says yes, but not by simply scaling the print files in a slicer. To maintain the proportions, the design would need to be redone in Fusion 360.

He also notes that the concept could be a good option for small all in one smart telescopes. That is worth paying attention to. The market is already moving toward compact imaging systems. A small automated shelter for that class of instrument seems less like a strange idea and more like an obvious missing product.

Files, Access, And The Real Skill Level Required

Engelbert has not made the print files publicly available. He will consider sharing them by request under certain conditions, especially for personal and noncommercial use, but he wants to understand what someone intends to do with them.

That may disappoint some readers, but it is reasonable. A project like this is not just a set of STL files. It is a collection of assumptions, adjustments, site conditions, assembly decisions, and electrical work. Releasing files without documentation could easily create more problems than it solves.

He is also clear about the skill level required.

“3D printing is only a part of building a dome, but not the only challenge,” he said. “Another one lies in assembling the printed parts, sticking and screwing them together, as well as installing the motors, wiring, and programming the control system.”

That is an important warning. A mini observatory can make astronomy easier after it is built. It does not mean the build itself is easy.

Still, that should not discourage the right person. It should just set expectations. If you can design, print, assemble, wire, test, and troubleshoot, this kind of project is now within reach. That was not true for most amateurs a generation ago.

Lessons Learned Along The Way

When I asked Engelbert what he would change if he started over today, his answer was specific.

He would make the inner half shells about 50 percent thinner to save weight. He would double the overlap from 5 cm to 10 cm for better weather protection. He would redesign the north side of the base and intermediate ring similar to the south side. He would also improve the limit switch design because the levers can bend during work on the dome or telescope.

The most difficult part of the design was deciding where to align the half shells and intermediate ring vertically on the cylindrical base. That decision affected the mount, optics, dome height, and usable field of view.

Another challenge was software related. He spent hours trying to control the RCCI ASCOM driver with an Arduino sketch before realizing that the driver did not work with the Arduino processors he normally used. Eventually, an older RCCI driver worked with an ATmega Uno.

Anyone who has worked on telescope automation knows this feeling. The hard part is not always the big mechanical idea. Sometimes it is the small compatibility issue that steals an entire evening.

What surprised him most was that the second dome went more smoothly than the first, even though he made some compromises. In the first dome, he had used high precision plastic rotational axes and aluminum strips for connections. In the second, he printed the axes himself and glued in printed connectors. Experience let him simplify the design without losing function.

That is how practical engineering usually improves. Not by adding more parts, but by knowing which parts can be made simpler.

A Builder’s View Of The Hobby

One of the things I appreciate about Engelbert’s answers is that he does not present technology as a shortcut around learning. He likes tools, automation, software, and experimentation, but he also respects the process.

When asked what advice he would give beginners inspired by projects like his, he did not tell them to jump straight into complex equipment.

“I’ve seen some people who wanted to jump right into using advanced equipment without understanding what’s actually feasible,” he said. “The many beautiful images on the internet lead beginners to believe that they can see galaxies or nebulae with their own eyes or that they can easily photograph them. To prevent them from losing interest too quickly because they’re overwhelmed by the equipment, I always advise beginners to start simple.”

That is good advice. It may not sell as many cameras, but it will keep more people in the hobby.

A simple camera and telephoto lens on a small GoTo mount can teach the fundamentals. The Moon, planets, bright clusters, and wide field targets are not lesser work. They are the foundation.

The irony is that the people best suited to build advanced automation are often the ones who learned the slow way first. They know what the system is supposed to do because they have done it manually. They understand why each step matters.

Automation without understanding is just a faster way to get confused.

Why This Matters For ScopeTrader Readers

ScopeTrader readers are gear people, but not only gear people. We care about instruments because instruments let us do something. They let us observe, image, measure, compare, learn, and sometimes contribute.

A mini observatory sits right at the intersection of gear and behavior. It changes how often you use the equipment you already own.

That may be the most important point in this whole story. The best telescope is not always the largest one. The best mount is not always the newest one. The best imaging system is often the one that is ready when the sky opens.

If you have to set up from scratch every time, you need a large block of time and a strong reason to begin. If your gear is already aligned, connected, covered, and waiting, the threshold drops. A two hour opening in the clouds becomes worth using. A weeknight becomes possible. A target can be gathered over many small sessions instead of one perfect night that never comes.

This is especially important as light pollution and weather challenge more observers. We can still travel to dark skies, and we should when we can. But a backyard system lets us keep working between those trips.

It also gives us control. If a cable fails, the telescope is outside, not across the country. If the clouds clear unexpectedly, the system is there. If maintenance is needed, you can do it yourself. You are not waiting in line for access to your own equipment.

That is not an argument against remote observatories. They serve a real purpose, especially for people chasing dark skies and long integrations. But Engelbert’s project reminds us that there is another path. Build smaller. Build closer. Build around your actual life.

Mini Observatories And The Future Of Backyard Astrophotography

Engelbert believes 3D printed observatories can become a viable option for amateur astrophotographers. After posting his dome on AstroBin and publishing an article in a German astronomy magazine, he received requests from around the world for print files and even purchase options.

“The demand is there,” he said, “and I think that one or two manufacturers will bring a similar product to market.”

I think he is probably right.

The timing makes sense. Small refractors have become very capable. Strain wave mounts have changed the way people think about portable payloads. Software like N.I.N.A. has made automation accessible. Smart telescopes have introduced a new class of users to compact imaging systems. At the same time, more amateurs are dealing with limited skies, limited time, and a desire to make their equipment easier to use.

A small automated observatory will not solve every problem. It will not make bad skies dark. It will not make clouds disappear. It will not turn a beginner into an expert overnight. But it can solve one of the most stubborn problems in amateur astronomy.

It can make the equipment ready.

That is not a small thing.

Engelbert’s dome is not a product pitch. It is one person’s answer to one person’s situation. That is what makes it useful. He had a limited view from the garden, better access from the garage roof, a desire to stop setting up every night, and the skills to build what he could not buy.

The result is a working micro observatory that protects a real imaging system, opens and closes under motor control, integrates with modern software, monitors weather, manages dew, and gives him more practical access to the sky he has.

That is the lesson I keep coming back to. We do not always need a bigger telescope. Sometimes we need a better way to use the telescope we already have.

For a lot of astrophotographers, the future may not begin with a remote pier in a desert. It may begin with a small dome in the backyard, a mini PC on the mount, a reliable weather monitor, and a system that is ready when the clouds move on.

That sounds less like a luxury and more like the natural next step.

 

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