Southern Cross Astronomical Clocks for Architecture & Luxury Interiors
Haute Horlogerie · Live Ephemeris Engine
Where Celestial Mechanics Converge with Interior Architecture
Sidereal Clocks grew out of the development of our working sidereal timepiece architecture. The celestial engine already exists: astronomical software, sidereal-time behaviour, ephemeris-based sky context, and paired Northern/Southern clock concepts. The next step is physical: translating those live celestial instruments into architectural timepieces for rooms, walls, galleries, and private spaces.
The Northern MovementAnticlockwise · Polaris & the Big Dipper
The Crux MovementClockwise · the Southern Cross
The golden rule
At midnight, the Cross points to the month.
Watch the hand through the night: about two hours takes it from one number to the next.
Look at the same time each night: about a month produces that same step.
Learn these two rhythms, and you begin to read the sky as both a clock and a calendar.
The clock is the teacher.
September
Southern Cross on Northern
Live: both faces are showing the sky right now.
Sidereal time --:--:--·--:--:--· Your meridian --Set to current time
Crux sits at declination −60°, below the northern dome, so it can never appear among these stars. The marker shows the Southern Cross as its exact mirror image, riding the mirrored Crux hand just as the real Cross rides the hand on the Southern dial.
How to read the hand
Watch the hand through the night: about two hours takes it from one number to the next. Look at the same time each night and it moves on by about ten seconds a day on the minute track: about a minute every six days, and over a thirty-day month about five minutes, the distance from XII to I. That is why a month sits in every five-minute space around the face. The Northern hand, mirrored onto the Big Dipper, keeps the same pace the other way round. Not exact mathematics, but true to the eye. Step through the months from April, midnight on 31 March 2026, and watch the hand walk one number per month.
The Sidereal Collection
Five instruments, one sky
Every instrument below is a Sidereal Clocks design, and every one already runs live in software. They were proved in public at CalculationTime.com, where they appear with permission.
The first instrument · June 2026
The Southern Cross Clock
The Cross itself becomes the hand, sweeping the southern sky around the pole. The instrument where the idea began.
A familiar twelve-hour face carrying a fourth hand through the Southern Cross, one needle bisecting Acrux and Gacrux from the pole, with the Sun, Moon, planets and months turning around it.
Proposed housings, frames, and finishes for translating the working sky engine into architectural form.
Optical Clarity & Display Engineering Direction
The physical editions are envisioned around a high-contrast circular display or dial system, protected by a clear architectural face and tuned for gallery, residence, and low-light interior settings. Final optical stack, movement, illumination, and enclosure details will be specified with manufacturing partners during prototype development.
Live Ephemeris Engine· Circular Architectural Display· Prototype Specification Stage
Architectural Finish I
Obsidian Anodized Aluminium
Envisioned as a dark satin aluminium frame option for minimalist contemporary residences, raw concrete walls, and polished basalt planes. Final alloy, surface treatment, and tolerances remain subject to manufacturing specification.
Architectural Finish II
Marine Brushed Brass & Bronze
Envisioned as a brass or bronze frame direction, drawing from marine chronometers and observatory instruments. Suppliers may propose the most practical grade, finish, sealing method, and fabrication pathway.
Architectural Finish III
Sovereign American Walnut
Envisioned as a timber-framed edition for private libraries, boardrooms, and warmer residential interiors. Wood species, machining method, finish, and metal detailing would be finalised through prototype fabrication.
Frame finish studies · concept renders. Final materials are specified with manufacturing partners.
Prototype-to-Installation Pathway
The working software can already render live sidereal readings and paired hemispheric clock concepts. Physical commissions would move through prototype specification, material selection, fabrication, calibration, and installation planning before any final production commitment.
Envisioned Physical Editions
Architectural Editions & Bespoke Commissions
Proposed scales for private galleries, atriums, and paired Northern/Southern installations.
Concept render · The Twin Clocks in walnut, showing the real Northern and Crux dials. Physical editions are at the prototype-specification stage.
Architectural Scale · 600mm Diameter
Proposed 600mm Salon Edition
A proposed architectural scale for private art galleries, formal dining salons, and executive penthouses. The working sky engine would drive the live sidereal display while frame, dial, lighting, and enclosure details are specified during prototype development.
Refined proportion for interior residences, galleries, and boardroom walls.
Monumental
900mm Architectural Concept
Larger physical format for atriums, private collections, and installation-scale interiors.
Bespoke Pair
The Twin Clocks
Proposed paired Northern and Southern displays for residences or spaces that want both hemispheres in dialogue.
For Architects, Interior Designers & Hospitality
A statement clock that keeps the sky
A Sidereal Clock is specified like a work of art: one wall, one room, one building, calibrated to its own time zone’s meridian. We work with architects, interior designers, hotels and private clients from the first sketch.
Private Residences
Libraries, salons & stairwells
A 600 mm or 900 mm luxury wall clock in walnut, brass or dark aluminium, or the Twin Clocks as a pair across a living room or gallery wall.
Hospitality
Hotel lobbies, bars & restaurants
A conversation piece for guests from everywhere: each clock is calibrated to one of twenty-four midnight-zero meridians, set to the hotel’s own time zone.
Workplace & Culture
Boardrooms, atriums & galleries
Architectural scale for headquarters, universities, museums and observatories, with finishes specified to the project and installation planned with the design team.
It began with a question. Somewhere in our own time zone, was there a place where the Southern Cross
would stand exactly upright at midnight, in step with the hands of an ordinary clock? We did the
mathematics and found Parkes, where the 33rd parallel passes within a few hundred metres of the great
telescope. The founder proved the working in public at
CalculationTime.com,
where the first faces still run.
Then the hand itself was redrawn: it stayed one line, but the angle changed, set to split the
difference exactly between Acrux and Gacrux rather than read either star alone. Its bearing moved by
a third of a degree, and the place moved with it, 35 kilometres due east along the same parallel to
Cumnock, New South Wales. The Dish still gives the clock its latitude. Cumnock holds its meridian.
At 00:00 on 1 April 2026, in standard time, the Crux hand reads exactly zero on that line. Every time
zone has one such meridian, about 15.04 degrees from the next rather than a flat 15, because a sidereal
day runs four minutes short of a solar one. These are the twenty-four meridians of the Sidereal Clock.
See all twenty-four meridians
Listed in the order midnight reaches them. Your own zone is highlighted.
A physical edition would be set to its zone’s meridian as standard, or calibrated to the exact
longitude of its installation wall as part of the commission brief.
A note from the founder
A clock that keeps the sky
The sky engine is finished. Every instrument in the collection runs live today, calibrated to one
time constant and checked against the ephemeris to a millionth of a degree. What remains is the part
that can only be done by hand and by machine: turning a proven celestial display into an object that
hangs on a wall for a lifetime.
Each physical edition will be made with specialist makers in dial and display fabrication, in
architectural enclosures of aluminium, brass, bronze and timber, and in the calibration that sets
every clock to its own meridian. The first editions will go to the people who register their
interest now.
If you have a wall, a room or a building that should keep the sky, I would be glad to hear from you.
— The founder, Sidereal Clocks
Physical Edition Enquiry
Register Interest in a Physical Edition
The software and live celestial display direction are already in motion. Physical editions will depend on prototype specification, material selection, fabrication partners, demand, and installation requirements. We are still determining realistic wait times for custom-made clocks; register interest now to secure consideration for a V1 allocation and early specification conversation.
Application Received
"Thank you. The founder reads every enquiry and will reply personally."
