Yes, where things are is 100% real. Set your location and the date and time, and NearLight computes the actual sky for that moment: about 8,000 real stars at their true positions, the real constellations, and the planets and Moon placed from NASA-grade orbital data (the Moon even rises and sets in step with the real one). All 110 Messier objects sit at their genuine spots, and the sky turns correctly through the night and across centuries, with true north, south, east and west. If NearLight shows Jupiter low in the southwest tonight, that’s where you’d actually find it outside.

They are. And that’s exactly the point this feature has to work around. It comes down to a mismatch between the sky, your eye, and a screen.

The planets really are tiny. Jupiter, even at its closest, spans only about 50 arcseconds of sky, less than 1/40th the width of the full Moon. Your eye can resolve detail down to roughly 1 arcminute (60 arcseconds), so a planet sits right at the edge of what the naked eye can separate from a star. That’s why, without a telescope, Jupiter and Saturn look like nothing more than bright dots — Galileo needed a telescope in 1610 to see that Jupiter even had a disc and moons.

A screen can’t show the sky at true scale. Held at arm’s length, a single pixel on your phone covers about the same 1 arcminute as your eye’s own limit. So if NearLight drew the sky at literal 1:1 scale, Jupiter would be about one pixel wide and Saturn’s rings would be smaller than a pixel, that means invisible. You’d see an empty black screen with a few dots, which is honest but useless.

Your eye and a monitor “run” very different resolutions. Your eye isn’t really higher-resolution than a screen. But it has a huge, continuous field of view and it constantly darts around, refocuses and adapts to brightness. A monitor is a fixed grid of pixels over a small window, so mapping the whole real sky onto it forces a choice: show everything and lose all detail, or show detail and only a tiny patch of sky. The eye+brain sidesteps that; a flat screen can’t.

So I make it a deliberate design choice. In the wide naked-eye view, objects are drawn a little larger and brighter than reality so they’re findable and enjoyable. The positions stay true, the apparent size and brightness are dialled up on purpose. And to actually see a planet’s disc, Saturn’s rings or Jupiter’s belts, you do the same thing you’d do outdoors: look through the telescope, whose eyepieces magnify the view.

So, that closeness isn’t faked, it’s simulated magnification, working exactly the way a real telescope does.

NearLight’s telescope is modelled on a classic ~102 mm (4″) refractor with a 1000 mm focal length — the kind of do-everything scope countless amateur astronomers actually own.

You look through it with a finder scope plus eight interchangeable eyepieces, each labelled with its apparent field of view (how wide the circle of sky looks to your eye).

Magnification is simply the telescope’s focal length divided by the eyepiece’s: a 10 mm eyepiece on a 1000 mm scope gives 100×. That’s why a shorter eyepiece zooms in more. NearLight shows a friendlier on-screen scale, but the lineup follows the real numbers:

• 38 mm — ~26×, 102° hyper-wide field. Best for sweeping the Milky Way and large open star clusters.
• 30 mm — ~33×, wide field (82°). Best for large nebulae and framing rich star fields.
• 24 mm — ~42×, Panoptic-class (68°). A comfortable “cruising” power — great for galaxies.
• 20 mm — ~50×, ultra-wide (86°). Best for the Andromeda Galaxy and bright deep-sky objects.
• 15 mm — ~67×, wide field (82°). Best for globular clusters and planetary nebulae.
• 10 mm — ~100×, Plössl (52°). The workhorse for the Moon and the brighter planets.
• 5 mm — ~200×, Plössl (52°). Best for detail like Jupiter’s belts and Saturn’s rings.
• 3.2 mm — ~313×, planetary ED (58°). Highest power, for splitting double stars and lunar close-ups.

Why these are the “most-used” ones: every real observer works across three regimes — low power to find and frame large objects, medium power for galaxies and nebulae, and high power for planets, the Moon and double stars. These eight focal lengths are the classic spread that covers all three with sensible steps between them, and they mirror the eyepiece designs amateurs genuinely reach for most (the workhorse Plössl at 52°, the immersive wide-fields at 82–86°, the beloved Panoptic-class at 68°).

You’ll also notice the highest powers are the least-used in practice: at 313× you’re already past what a 102 mm scope and the atmosphere can usefully resolve — which is exactly why most observers spend their time on the middle of the range. NearLight even models that, dimming the view as you push the magnification, just like real optics.

With today’s chemical propulsion, even the outer planets of our own Solar System take years to reach — and crossing to another star system is simply out of reach. So I built a physically accurate simulator of the kind of propulsion that would get a spacecraft to a nearby world in days, or to neighbouring stars within a human lifetime.

The ship in NearLight runs in one of two modes: it either cruises instantly at a chosen fraction of the speed of light, or it accelerates and brakes at a chosen g-force (Brachistochrone). Both modes apply special-relativistic time dilation. Every calculation assumes a 10-tonne spacecraft — the small blue orb you see tracing its trajectory through the scene.

Let’s be honest: the energy these engines would demand is, for now, essentially impossible to produce. But if humanity ever does build something like the drives we know from sci-fi — Interstellar, Project Hail Mary, Alien, Star Trek — NearLight is your go-to simulator.

Since there are enormous amounts of spacecraft and mission goals available in real life, I had to center the idea around a spacecraft with a mass of 10 tons that can carry enough propellant to at least reach Neptune with a single Lambert transfer.

In reality, multiple transfers and gravity assists are used to save fuel, but that’s incredibly difficult to calculate and visualize in an app. There’s a reason NASA supercomputers exist. 🙂

So, while the physics and calculations are real, the spacecraft simply carries a bit more propellant. The Classical Mode has one main purpose: to illustrate just how incredibly slow we currently are, and that reaching another planet requires us to use everything we have just to gain a few km/s against the target and then wait months or even years to arrive there.

Insane thought, isn’t it? So that’s why the other travel modes exist.

One day, we’ll need them.

In reality, most departure and capture burns during interplanetary missions last only a few minutes. After that, the spacecraft spends months or even years coasting through space with little or no propulsion.

NearLight intentionally visualizes these burns over a much longer period – on purpose. If they were shown at their real duration, they would be almost invisible compared to a journey that may take hundreds or thousands of days. By extending the burn phase, users can better understand when and where energy is added to the mission, how transfer trajectories are created, and how a spacecraft gradually leaves one orbit and enters another.

The displayed burn duration is therefore a visual and educational aid. The underlying orbital mechanics, transfer calculations, travel times, and trajectories remain based on real physics.

Yes, if it where real scale, you´d be zooming and moving your mouse or finger for ages, trying to find a needle in a haystack (called “planet”) in the vast emptiness.

If the Sun is the size of a pea, Earth would be 70cm away with the size of a grain of sand. Go try to find that in the dark. Now imagine Jupiter, 4m away from that pea or Pluto 30m away from the pea-sun, impossible to see with the naked eye. Well, the sun still has 99,5% of the mass of solar system, think about that for a second…

You guessed it. If i didn´t scale everything (distances visually shorter, planets visually bigger), you´d be giving the app less than a star, not having any fun. As a matter of fact, the distances are accurate, only the visuals help you find everything.

Yes. The app is built around real nearby star systems and their known astronomical data from NASA and ESA Missions.

NearLight currently focuses on nearby star systems from a curated catalog of around 100 lightyears, so not every star in the sky is included. Some stars may be missing because they are outside the current catalog radius, have incomplete source data, or are listed under a different catalog identifier or alias. If you do not find a star, try a common alternate name, HIP number, or catalog ID. I will also improve the database over time, so additional stars and metadata may appear in future updates.

Yes, partially. On release, NearLight includes exoplanet host name and shows known planets for selected systems. In further releases a more detailed view might be implemented.

Some stars have limited public data or incomplete catalog metadata, so not every star has full physical details, aliases, or exoplanet information yet.

ETT means Earth Travel Time. It shows how long the trip would take as measured from Earth. OTT means Onboard Travel Time. It is the time experienced by the traveler on the spaceship, including relativistic effects.

Time dilation is the difference between Earth time and onboard travel time in a spaceship at high speeds, especially near the speed of light. Time passes differently for each observer.

Time Dilation also happens when closing in on a black hole. With NearLight, you can see these effects with moving clocks by simply dragging the slider to change the distance to the black hole, or the spin, or it´s mass.

Ever seen Interstallar or the recent movie Project Hail Mary? Their physics are quite real and show time dilation in a meaningful way.

The Lorentz factor, written as γ (gamma), is a core part of special relativity. It describes how time, length, and mass-related measurements change as an object moves closer to the speed of light. In NearLight, it is used to show how Onboard Travel Time (OTT) changes compared with Earth Travel Time (ETT) at relativistic speeds.

The formula is:

Where:

• v = the ship’s speed
• c = the speed of light

As v gets closer to c, the Lorentz factor grows very large. That is why time onboard the ship appears to slow down relative to Earth.

For travel time, a simple form is:

“β” (beta) is simply the ship’s speed written as a fraction of the speed of light — β = 0.5 is half light speed, β = 0.999 is 99.9 % of it.

• Real β ON — the ship’s true speed. Under constant 1 g thrust it races to ~99.999 % of light speed within about a year, then stays pinned just below it for almost the whole trip. So the gauge jumps close to light speed almost immediately and barely changes after that.
• Real β OFF — a gentler “how fast it looks crossing the map” gauge: slow at the start, fastest in the middle, slowing into the destination. Easier to follow with your eyes, but it’s not the real speed.

An analogy: Imagine flooring a car that could accelerate forever. Normally the speedometer would just keep climbing — but the universe has a hard speed limit: the speed of light (c). So instead of running away, the needle slams up against that wall and then inches closer and closer to it, never quite touching it. That’s why the real speed looks “stuck” near light speed for almost the entire journey.

It’s also why the clocks disagree so wildly. That close to light speed, time on board slows to a crawl: a handful of years pass for the crew while thousands pass back on Earth. With Real β on you can see you really are at the edge of light speed — with it off, the slow-looking gauge can fool you into thinking you’ve barely started, even as Earth’s calendar races ahead.

Well basically everything is outlined in Kip Thornes paper and he explains it why. 

Long story shot: a spin with a higher value would lead to the black hole falling/ripping appart. There´s an electromagnetic antiforce that prevents exactly that, which pins the spin at 0.9982. Nature is strange. So that´s why black holes don´t dissapear. For Interstellar, they had to magically let the spin go to 0.99999….to make the physics possible. At least in the movie.

A lot of ideas are in my head.

The star systems data will be expanded over time, including temperatures, masses, etc. I am thinking about an Exoplanet Dataset and other nice to have features.

But the main focus stays on time dilation and how it affects the clocks and travel times. One feature i´d love to make is simulating a journey the end/beginning of the observable universe, which, theoreticly could be possible within a human lifetime. The only downside is the time that passes on earth. There´d probably be no-one left to tell the story….

New features with time and love.

Currently not. But it´s not ruled out on future releases. Depending on the initial success of the app, i will promise to make an Apple Vision app once the threshold of the devices price is met in sold apps. 🙂 If you want to help the development, please feel free to review the app on the store and help promoting it to other physics fans out there.

What once started as a project for myself (let´s see if any of those movies are right), ended up in a small calculator app and got bigger and bigger with each revision. It´s one thing to ask an AI about hard facts, it´s another one to get a feeling for it and seeing the time go by on different clocks. 

I am a 51 year old brand agency owner and web developer from Germany. So that profession background helped a bit by creating the visuals and style of NearLight. I hope you enjoy the app! Leave a review if you like it and want to support the app.