The Ephemeris Circle
T+ —  ·  by DistanceToPlanets.com
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est. for the orbit-obsessed

THE
EPHEMERIS CIRCLE

also known, fondly, as The Orrery

A Discord for people who track real spacecraft, compute real transfer windows, and get genuinely irritated by a movie's orbital mechanics. Trajectories. Light-time. Precision. Persistence.

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Run by DistanceToPlanets.com

live ephemeris —
Earth → Sun light-time, right now
8m 19.0s
Sun–Earth distance: 149,600,000 km
meaning the sunlight on your screen left the photosphere 8 minutes, 19 seconds ago.
Earth–Mars distance— AU
Mars one-way light-time—
Earth orbital speed29.78 km/s
Voyager 1 distance (approx.)—
positions: simplified circular-mean elements, J2000 epoch · data via DistanceToPlanets.com UTC —
01 · membership

Who finds a seat here

Δv

The trajectory people

You've run a Hohmann transfer by hand at least once. Porkchop plots make you happy in a way you've stopped trying to explain to people.

τ

The light-time pedants

You know there's a difference between "Mars is at opposition" and "the picture you're looking at is current." You will say so.

⟲

The satellite watchers

TLEs, pass predictions, the ISS overhead at dusk. You've stood in a backyard at the right minute more than once.

∞

The patient ones

Multi-year cruise phases don't bore you. You understand that the interesting part is often the part where nothing visibly happens.

02 · inside

What's actually in the server

#mission-tracking
Live threads on active missions — burns, flybys, comms windows, the moments where a spacecraft does something and you want to talk about it within the hour.
#orbital-mechanics
Worked problems, transfer windows, n-body weirdness, and the occasional argument about perturbation methods that runs four days too long.
#satellite-tracking
TLEs, pass predictions, ground station chatter, and people comparing notes on what they caught through a finderscope last night.
#instruments-and-gear
Telescopes, trackers, the homebrew rigs people build to log their own ephemerides. Hardware talk, not hype.
#the-archive
Long-form posts worth keeping — mission retrospectives, derivations, the kind of thing you'd want to find again in two years.
acquisition of signal

Join the Circle

No quiz at the door. Just bring whatever you're tracking, computing, or watching pass overhead tonight.

Enter the Discord
discord.gg/9UuxY6ZeA
A community run by DistanceToPlanets.com
Contact: distancetoplanets@proton.me