About DarkSky Index
DarkSky Index turns a dark sky into something a guest can check before they book. For a property it computes a 90-night outlook of how dark each night will be, and publishes it as a page you can share and a widget you can embed. It is built for hosts of short-term rentals, eco-lodges, and astro-tourism stays, the places where the sky is genuinely part of what a guest is paying for.
Why it exists
Any listing can say “great stargazing”, so guests have learned to discount it. The claim costs nothing to make and cannot be checked. A dated forecast is different: it can be wrong, which is exactly what makes it worth believing. Publishing one is a way of saying the sky is worth planning around on these specific nights, and being held to it.
How the rating is computed
Darkness is astronomy. Moon phase, moonrise and moonset, Milky Way core altitude, and the rated peaks of real meteor showers are computed for a property’s exact coordinates, using the same deterministic engine for every property. Two places with the same sky get the same answer. Nothing about the rating is tuned, weighted commercially, or adjusted to make a listing look better than it is.
The things we will not do
Cloud cover is a separate overlay for the nearest nights, shown beside the darkness rating and never blended into it. Weather more than about two weeks out is not reliable, and folding it into a 90-night score would produce a number that looks confident and means very little.
The Bortle sky-quality value is estimated from satellite light-pollution data, not a site meter, and it is labelled as an estimate everywhere it appears. Where there is no data for a location, the page says so rather than showing a class we cannot stand behind.
We never fabricate data, hosts, testimonials, or reviews. Example content on this site uses real places and real computed data, and is labelled as an example. If you find something on this site that reads as a claim we cannot support, that is a bug worth reporting.
What it costs
One price per property, with a free trial and no card required to start. The current plans and what happens at the end of the trial are on the pricing page.
Contact
Questions, corrections, and bug reports go to support@darkskyindex.com.