Astronomy · stargazing · space science

The sky is out there. Start gazing.

Celestial event previews, plain-language science explainers, and honest gear notes — written by an amateur astronomer in Cyprus. 3–5 articles a week. No cosmic ballet.

An amateur astronomer stands beside a large Dobsonian telescope at dusk in the Negev desert, ready for a night of stargazing

Gear

Collimating a Dobsonian after the drive: the two tools that matter

Every time I load the 8-inch Dob into the back of the car and drive the hour up to Troodos, it arrives out of collimation. Not badly (the mirror doesn’t slide across the cell), but enough that a defocused star at 200× shows the diffraction rings piled up on one side instead of sitting concentric. On an f/6 tube that costs me a sliver of sharpness on Saturn; on a faster f/4 it would gut the whole view. Before I look at anything, I spend ninety seconds putting the optics back into line. This is that routine: what collimation actually is, the two tools worth carrying, the one trick that makes a cheap laser trustworthy, and the star test that tells you when you’re done. ...

JWST NIRSpec transit light curves of the hot gas giant WASP-39 b: three data series at 3.0, 4.3 and 4.7 μm dip as the planet crosses its star, with the 4.3-micron curve sitting lowest because carbon dioxide in the atmosphere absorbs that wavelength; set over an artist's illustration of the planet and its Sun-like star.

AI × astronomy

Exoformer: a transformer that cuts JWST atmosphere retrievals from weeks to days

Running a full atmospheric retrieval on a JWST transmission spectrum of WASP-39b took about 498 hours of compute with standard settings, roughly three weeks of a core grinding away. A new transformer neural network gets the same answer in about 64. Same retrieval code, same Bayesian machinery, same posterior at the end. It just starts the search in a far better place. The paper is Exoformer: Accelerating Bayesian atmospheric retrievals with transformer neural networks, led by L. Pagliaro and published in Astronomy & Astrophysics this spring. I spent years training neural nets before I started pointing a Seestar off my balcony in Nicosia, and what I like about this one is what it refuses to do. It doesn’t hand you an answer from a black box you can’t check. It speeds up the slow, principled method by giving it a good first guess. ...

Artist's concept of a young star surrounded by a bright, dusty protoplanetary disk of gas and dust seen nearly edge-on (NASA/JPL-Caltech illustration).

Space science

How planet-forming disks lose their gas: JWST mapped the winds in 72 young stars

Every planet, ours included, assembled inside a flat disk of gas and dust that has since vanished. That disk is the raw material and the deadline at once: it survives only a few million years around a young star before the gas is gone, and any world that wants a thick hydrogen-helium atmosphere has to grab it before the tank runs dry. A new study led by Naman Bajaj at the University of Arizona used JWST to watch that gas actually leaving, mapping the jets and winds carrying it off in 72 young disks and showing how the escape route changes as a disk ages. The paper, “JWST/MIRI Reveals the Evolution from Molecular to Atomic Disk Winds”, is one of the largest JWST disk-wind surveys to date. ...

A crescent Moon with faint earthshine at right, the overexposed point of Venus at center, and Earth's blue atmospheric limb at lower left, photographed from the ISS

Celestial event

Venus hits its brightest for 2026 on September 18 — catch it low in the west now

Venus is about to be the brightest it gets all year. On the evening of September 18, 2026, it reaches greatest brilliancy at about magnitude −4.8, outshining everything in the sky except the Sun and Moon. The catch, if you’re watching from the eastern Mediterranean like I am at 35°N, is that this is a low, quick apparition: Venus sits close to the western horizon after sunset and drops out of view inside about an hour. You don’t need any gear — it’s a naked-eye object that punches straight through city light — but you do need a clear line to the west-southwest and the discipline to be outside on time. The best single evening is September 14, when a thin crescent Moon parks within 5° of it. ...

A waxing gibbous Moon through a telescope, craters and mountains thrown into sharp relief along the terminator, the day–night line running down the left of the disc.

Beginner stargazing

Moon phases, explained: how the lunar cycle sets your dark-sky nights

The single biggest thing standing between you and a good night under the stars isn’t your gear, your location, or even the weather. It’s the Moon. A full Moon can raise the brightness of the whole sky enough to erase the Milky Way, wash out every meteor fainter than a fireball, and flatten a galaxy into a grey smudge. A week later the same sky, from the same spot, with the same eyes, shows all of it. Nothing changed but the phase. ...

Artist's concept of NASA's Nancy Grace Roman Space Telescope (formerly WFIRST), a Hubble-sized survey observatory, shown against a star field

Space news

The Roman Space Telescope launches today — what it changes for the rest of us

As I write this, NASA’s Nancy Grace Roman Space Telescope is bolted to the top of a SpaceX Falcon Heavy at Launch Complex 39A in Florida, and the countdown is running. Liftoff is set for 07:26 EDT: 11:26 UTC, or 14:26 here in Nicosia. NASA’s live coverage starts at 10:20 UTC on NASA+ and YouTube. If weather or a last-minute hold gets in the way, the backup window opens tomorrow morning at 11:22 UTC. ...

The twin-peaked island of Skellig Michael rising steeply from the Atlantic off the Iveragh Peninsula in County Kerry, with waves breaking at its base

Astrotourism

Stargazing in Kerry: the Northern Hemisphere's first gold-tier dark sky reserve

If you want a genuinely dark sky and you’d rather not leave Europe to find one, the Iveragh Peninsula in southwest Ireland is about as good as it gets. The Kerry International Dark Sky Reserve covers roughly 700 km² of the peninsula and was certified gold tier — the top rating — by the International Dark-Sky Association on 27 January 2014. It was the first gold-tier reserve named anywhere in the Northern Hemisphere, and it’s still one of only a handful worldwide. ...

Silhouette of an amateur astronomer beside a Newtonian reflector telescope against deep-blue desert twilight.

Gear

How to keep dew off your telescope: shields, heater straps, and when you need them

Somewhere in the next few weeks the first properly damp night of autumn will cut an observing session short, and it won’t be cloud that does it. A film of water forms on the front of the telescope, the stars go soft, then milky, then gone, and you spend twenty minutes with a battery hairdryer wondering where the sky went. That’s dew, and it’s the most avoidable way to lose a clear night. Here’s what forms it, what stops it, and where you can stop spending — because the cheapest fix is often enough, and some of you don’t need to buy anything at all. ...

Hubble image of galaxy cluster SDSS J1038+4849: two bright yellow galaxies flanked by curved blue arcs of strong gravitational lensing that form a smiling-face pattern, against a field of faint distant galaxies.

AI × astronomy

How Euclid's AI finds gravitational lenses: five neural networks and a million galaxies

Euclid’s first quick data release covered 63 square degrees, about 0.45% of the sky the mission will eventually map, and in that sliver it turned up 497 galaxy-galaxy strong gravitational lenses. Of those, 250 are grade A candidates, and 243 had never been published before. In one fraction of one percent of the survey, the team doubled the number of strong lens candidates ever found with space-based imaging. That’s the headline. The part I keep coming back to, as someone who spent years training image classifiers before I spent my evenings pointing a Seestar off a Nicosia balcony, is how they did it. It wasn’t one clever network. It was five different neural networks feeding a funnel of human eyes, and the honest lessons about which models worked, where they failed, and why you still can’t cut the humans out are more interesting than the pretty arcs. ...

A JWST NIRCam deep field crowded with hundreds of faint galaxies, with a small cutout highlighting the distant galaxy JADES-GS-z6 as a blurry blue-and-red smudge.

Space science

The first massive galaxies may weigh four times what we thought — hidden in faint dwarf stars

When you weigh a galaxy, you’re really weighing its light. Point a telescope at an elliptical galaxy a few billion light-years away and you record a smear of photons, and most of that light comes from a small number of bright, heavy stars. The faint red dwarfs, the ones that make up the overwhelming majority of any galaxy’s star count, are individually invisible at that distance. You never see them one by one. You infer how many there are, and you do that by assuming a galaxy far away is built from the same mix of stars as the ones nearby. ...