Tonight’s sky, astronomy tools and a telescope buying guide
Browse without JavaScript: the full catalogue. For AI agents: llms.txt and data/index.json.
Browse without JavaScript: the full catalogue. For AI agents: llms.txt and data/index.json.
An independent night sky companion: tonight’s forecast and what’s up, a set of simple astronomy tools, and a buying guide that ranks equipment by how well it fits your answers and how widely it is owned and recommended.
Cloud forecasts come from Open-Meteo; the cloud map shows the Met Office, DWD and ECMWF models from Open-Meteo’s open data (CC BY 4.0). Darkness, the Moon, planet positions and which targets suit your night are calculated in your browser from a catalogue of over 200 objects. Light pollution is modelled from NASA’s Black Marble night-lights imagery. Equipment specifications are compiled from manufacturer information and published reviews; prices are typical new street prices in US dollars, converted to your currency for convenience. The retailer’s page always has the final word.
Every product picture is drawn on the fly, so proportions follow the data but details are simplified. In the sky map, galaxies and nebulae are real photographs from the Digitized Sky Survey (STScI/NASA, colour by CDS) and the Moon is the public-domain Clementine map (USGS/PDS), both streamed from the CDS HiPS service.
Stars come from ESA’s Hipparcos catalogue and the Yale Bright Star Catalogue, star names from the IAU, constellation boundaries from the IAU (via CDS), and constellation figures and the Milky Way outline from d3-celestial by Olaf Frohn (BSD licence).
There are no accounts and no tracking cookies. Your answers stay in the page address so a result can be shared. Your profile (your places, gear and settings, under Me) is kept in this browser only; you can save it to a file and load it on another device. Your location is sent only to Open-Meteo (for the forecast and time zone) and BigDataCloud (to name your area). The light pollution map loads map tiles from OpenStreetMap and NASA for the area you look at. The sky map loads survey photographs and the Moon map from CDS (Strasbourg) for the part of the sky you look at. The Space weather page loads data from NOAA’s Space Weather Prediction Center and pictures of the Sun from NASA and ESA. The 3D universe shows planet and moon maps from NASA, USGS, JPL and ESA and galaxy photographs from the Digitized Sky Survey, served by CDS. Comet orbits come from the IAU Minor Planet Center and satellite orbits from CelesTrak, worked out with the satellite.js library. The cloud map reads Open-Meteo’s forecast files from Amazon Web Services and its map layer from unpkg, for the area you look at. If you use the assistant, your questions, the chat so far and the context sent with them (the object you asked about, your place to about a kilometre, the time, your sky and your equipment) go to the site’s assistant server and on to the AI company that answers, such as Anthropic or Google. The server keeps no copy; to limit questions per day it counts them under a scrambled form of your internet address that changes daily and is deleted after two days.
Everything is open data: see llms.txt, data/index.json and the script-free catalogue.