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Celebration Constellation: Cassiopeia, on a table full of glasses

Oct 13
3 min read

A photo of a table from above, its glasses, caps and plates matched against the real sky, and the constellation they make.

A round wooden table seen from above in a violet night tint, covered in bottles, glasses, bowls and plates; orange rings mark the round objects and white star dots of different sizes are scattered across the whole picture, several of them sitting inside the rings.

The table as Cassiopeia: 13 of the 28 circles the app found hold a star from that part of the sky. Synthwave colourised background, 1600 × 1201 px.

Look down at a table after a long evening and you see circles everywhere: glass rims, bottle caps, plates, a bowl. Which constellation do they make? Celebration Constellation finds the round things in a photo, treats their centres as a pattern of points, and searches the sky for stars in the same arrangement.

Below is how this one came out, in four steps, and what the download holds. The piece needs its photo, so open the app and use a table of your own.

How this one got made

Twenty-eight circles, found on upload

Upload a photo taken from straight above under Upload a photo. This one is a round pine table with about forty bottles, glasses, caps and plates on it. Detection runs by itself once the photo lands, with Object size on Auto guessing how big the circles should be.

A round pine table photographed from directly above, lit warm from one side: green and brown bottles, empty wine glasses, tumblers, a pink bowl, plates with forks, bottle caps, a bowl of wrapped sweets on a chopping board and a folded magazine.

The input, as uploaded. The printed face in the magazine is pixelated here and in every render below.

It found 28. I use a classic Hough circle transform for this, because rims and caps seen from above are near-perfect circles, the one case where that old method beats heavier detectors. Not every rim gets a ring, and that is fine: the pattern only has to be the table's own.

Cassiopeia comes out on top

The app samples 100 patches of the sky, turns, scales and moves the pattern over each one, and counts how many circles end up holding a star.

Three panels: the table in dark grey with 28 orange rings; the same rings on a dark ground with the white stars of one patch of sky turned to fit, filled where a star falls inside; and the table with the rings and stars together.

Found, fitted, overlaid: the middle panel is the step you never see in the app, one patch of sky turned until the most rings land on stars.

I rank the matches by that count, because it is exactly what you can see in the picture. The name sits above the render, with the rank, the count and a verdict.

The match header: Cassiopeia in bold, under it "Match 1/100 · 13/28 circles matched · Moderate", with left and right arrow buttons either side and the top of the violet render below.

The payoff: which constellation, and how many of your circles it explains.

Moderate means between 30% and 60% of the circles hold a star. It is a party app, so a plausible match is enough, and the verdict tells you how plausible. The arrows either side of the name step through the other 99. The search is seeded, so the same photo with the same settings lands on Cassiopeia again.

The table stays under the stars

Background decides what the stars are drawn over. Black and Synthwave gradient drop the photo; Dark greyscale and Synthwave colourised keep the table visible under the rings.

Four versions of the same match in a two-by-two grid: rings and stars on plain black, on a purple-to-blue gradient, over the table in dark grey, and over the table tinted violet.

Black, Synthwave gradient, Dark greyscale, Synthwave colourised: only the bottom two still show that it was a table.

Synthwave colourised keeps the glasses readable and turns the table into a night. That is the one above.

Cassiopeia, seen from Freiburg

Under the render, Mini starmap plots the matched patch in your own sky. Type your Latitude (°) and Longitude (°), or use Your location. For Freiburg, 47.99° and 7.85°:

A round sky chart on a dark ground: the horizon as a circle with N, E, S and W around it, faint grey background stars, and in the north-west, about halfway between horizon and centre, a blue box full of white stars with a yellow star marker at its centre, labelled Image footprint.

The blue box is the photo's patch of sky and the yellow star marks its centre: north-west and about halfway up, seen from Freiburg at 07:28 on 29 September.

The outer circle is the horizon and the centre is straight up; How to read this map under it says which way to face.

From screen to object

Constellation (PNG) is the download: the render as you set it, with the star catalogue credits written into the file. Sources and credits names them, the Yale Bright Star Catalogue and the IAU constellation boundaries, both public domain. A print can be ordered from Order a print of this creation.

The Downloads heading with a full-width Constellation (PNG) button, then folded panels for Sources and credits and Order a print of this creation.

One file, its credits, and the print.

Other controls, one line each

  • Detection sensitivity, under Advanced settings: lower finds more circles, higher keeps only crisp rims.

  • Search thoroughness: how many patches of sky get tried; more is slower.

  • Search area size (°): how wide each patch is.

  • Circles and Stars: show or hide either layer.

  • Star colour: Colour by B–V paints each star its temperature colour, exaggerated so it reads on a photo.

  • Star size: bigger stars read better in print.

Changes to the detection settings apply when you press Run.

Your turn

Open the app, photograph your own table from straight above, and see what it matches. Then send me what you made. I'll ask before I show it anywhere.

 
 
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