Astronomy, Engineering, Automation, Making

How We Hacked a 50-Year-Old German Giant

The Stardome Carl Zeiss retrofit: Software Bisque electronics, custom engineering, an angle grinder, and a bottle of chocolate sauce.

How We Hacked a 50-Year-Old German Giant: The Great Stardome Zeiss Upgrade

If you’ve ever looked at a piece of vintage machinery and thought, “I can make this smart, robotic, and controllable via a laptop,” you’re either a genius or you haven't realized what you’re getting yourself into yet.

A few years back, we set out to upgrade the iconic 50-year-old Carl Zeiss Jena telescope at Stardome Observatory. The goal? Turn a historic piece of optical heritage into a fully automated, GOTO-capable research beast—without ruining its classic aesthetic or spending half a million dollars on a brand-new scope.

What followed was a masterclass in high-tech engineering, precision CAD modeling, industrial casting, and... balancing a multi-hundred-kilogram steel monster using a bottle of dish soap and a tub of chocolate sauce.

Here is the story behind the project.

Phase 1: From Kumeu to Stardome

Our confidence in taking on a 50-year-old East German giant actually came from an earlier project at Kumeu Observatory. Kumeu had a 15-year-old mount that was well outside its warranty period. Software Bisque helped us upgrade that system, and because their TCS (Telescope Control System) drive electronics worked so brilliantly there, we realized we could retrofit the exact same research-grade technology onto the Zeiss.

As the guy handling the control systems, wiring, and Software Bisque integration, my challenge was figuring out how to thread modern circuit boards, optical homing sensors, and USB cabling through a 1960s cast-iron German housing. Easy, right?

 [ Zeiss Telescope Housing ] 
            │
            ├─► 1. Strip 500kg of precision metal
            ├─► 2. Reverse-engineer zero existing CAD drawings
            ├─► 3. Wire USB & power through a 2-meter twisting core
            └─► 4. Apply high-precision counterweights (Chocolate Sauce)

Phase 2: No Drawings, No Problem (Enter the CAD Wizards)

When you pull apart a modern telescope, you get a manual or a schematic. When you pull apart a 1960s Zeiss, you get mysterious East German engineering and zero original CAD drawings.

Tony Messenger (our engineering mastermind), Andreas (our 3D CAD wizard), and the team spent weeks reverse-engineering the mount:

The Great Gear Mystery: The original Right Ascension (RA) worm gear was surprisingly pristine after 50 years of nightly use, but it wasn't perfectly cylindrical. We had to lathe-dress it and design custom sleeves and bearing housings just to attach modern drive belts.
Hidden Space inside the Declination Axis: When we pulled the Dec shaft apart, we found a complex internal braking system that nobody had looked at in half a century. But Tony made a discovery: the inner diameter of the brake collar had just enough clearance. If we machined a slot in the side, we could tuck the new worm gear completely inside the housing—keeping the original exterior lines of the scope untouched.

Phase 3: High-Tech Engineering vs. The Home Saw

While Pakuranga Engineering was doing heavy precision milling on industrial machinery, we were back at the dome doing some... agricultural modifications of our own.

To get the new timing belts and my drive cabling through the original cast-iron housing, we brought out a strictly high-tech tool kit:

Tool #1: A cordless drill.
Tool #2: A hole saw.
Tool #3: An angle grinder.
Tool #4: A hand file and sheer perseverance.

There is nothing quite like taking an angle grinder to an irreplaceable piece of astronomical history to get your heart rate up for the morning.

Phase 4: Industrial Sand-Casting & A Stolen Car

Because nothing on a 50-year-old German scope standardizes with off-the-shelf hardware parts, we needed a new cast-iron mounting boss nearly half a meter in diameter.

We took Andreas’s 3D CAD renders down to a heavy rail foundry in Otahuhu. These guys were used to casting massive train components, so when we asked for a delicate, ultra-precise telescope component, they packed sand around the pattern and poured molten iron like it was just another Tuesday.

Of course, no project is complete without a bit of chaos.

We wanted to touch up the original Zeiss paint. Grant had arranged for custom spray cans color-matched to the original Zeiss enamel, and he had one of the telescope’s original access doors in the back of his car to test the match.

The next morning: Grant's car was stolen—along with the irreplaceable Zeiss door.

Somewhere in Auckland, a car thief opened a stolen boot and wondered why on earth someone was hoarding a single, heavy grey metal panel with German writing on it.

Phase 5: The Chocolate Sauce Counterweight Incident

After months of precision machining, 3D printing custom homing sensor mounts, and feeding meters of USB and power cables through the hollow interior shaft, it was time to wire up the boards and test the software.

Because of how the internal cable loop ran, Tony and I spent a full day and night feeding five heavy cable runs through the hollow core so the scope could rotate without binding. But to test the motors and optical home sensors on TheSkyX, we needed to drive the mount before reinstalling the main telescope tube and counterweights.

The problem? Without the tube, the Dec axis was wildly out of balance. We couldn't run the high-precision motors without risk under the offset load.

I had a theory: Zeiss probably designed this so the mount is almost balanced on its own without the telescope or counterweights. We just needed a tiny bit of extra mass to offset the new hardware.

Enter the highest-precision counterweights known to science:

One bottle of liquid hand soap
One plastic squeeze bottle of chocolate ice-cream topping

We taped the chocolate sauce to the housing, powered up the TCS board, and hit "Home Mount" in TheSkyX.

The motors whirred smoothly, the optical homing sensors tripped perfectly, and the entire mount tracked across the sky—driven by Software Bisque electronics, managed by laptop, and balanced by chocolate syrup.

Phase 6: Bringing 1968 into the 21st Century

Today, the Stardome Zeiss is a totally different beast under the hood:

Full Computer Control: Click a target on TheSkyX software, and both the telescope and the observatory dome move in perfect synchronization.
Modern Astrophotography Ready: Internal USB and power routing mean cameras, filter wheels, and autoguiders plug straight into the back without a single cable getting tangled as the scope flips across the meridian.
Preserved History: From the outside, the scope still looks like the majestic, mechanical giant installed decades ago.

It took hundreds of hours, custom sand-cast iron, precision CAD models from Andreas, heavy machining by Pakuranga Engineering, a bit of wiring magic, an angle grinder, and some dessert toppings—but we brought one of New Zealand's most famous telescopes into the modern era!