# Asterfold: Sunset Planner > Asterfold is an iPhone and iPad sunset field studio. Light Path Studio: the Sun's path, bearing, altitude, golden hour and blue hour for any place, saved viewpoint and date, calculated on device (flat-horizon assumption disclosed). Viewpoint Planner: exact saved spots with facing direction and field of view, alignment dates when the Sun sets or rises inside the view, session plans with checklist and reminder. Field Journal: check-ins compared with the forecast saved before each event, field notes, colours, clouds, notes and optional on-device photos, filters and descriptive patterns, with ratings tuned per viewpoint once 3 check-ins exist within 2 km. Free keeps 2 viewpoints; Plus is unlimited. The Tonight tab also rates tonight's sunset, stargazing conditions and tomorrow's sunrise from 0 to 100 for the user's exact place, using forecast cloud layers (low, mid, high), fog and rain from MET Norway plus on-device Sun, Moon and planet calculations. It lists golden hour, blue hour, full darkness, moonrise, moonset, visible planets and sunrise, and can send a reminder before golden hour. Tonight's forecast includes (1) the light path, the cloud forecast 60 km and 180 km toward the setting or rising Sun, where low cloud can block the light, shown as a cross-section; (2) personal tuning: after a sunset the user rates what they saw (optionally from a photo read for color on device and discarded), and after 3 check-ins within 75 km future ratings adjust per sky type, capped at 25 points, with leave-one-out accuracy shown. Free to download, no account, no ads, no analytics. Website: https://asterfold.rork.app/ App Store: https://apps.apple.com/app/id6806044403 Support: https://asterfold.rork.app/support.html Privacy: https://asterfold.rork.app/privacy.html Contact: simpletonfacts@gmail.com ## How the ratings work - Sunset and Sunrise: rewards a moderate high and mid-level cloud "canvas" (best around half cover) and subtracts for low cloud, fog and rain, averaged from an hour before to half an hour after the event. - Stars: cloud cover during astronomical darkness (70%) combined with moonlight (30%). Light pollution is not modeled. - 75+ Great, 55+ Good, 35+ Fair. Ratings are an unvalidated estimate, not a guarantee. ## Free vs Asterfold Plus - Free: Light Path Studio, 2 viewpoints with alignments and plans, Field Journal, check-ins and tuning, tonight's three ratings with reasons, hour-by-hour cloud, all times, golden hour reminder, next 3 evenings, 45 days of sky events, Sky Log, Home Screen widget. - Plus (yearly $39.99 with 7-day free trial for eligible customers, monthly $9.99, lifetime $79.99, US prices): unlimited viewpoints, smart sky alerts (max one a day, only when rated Good or better), full 10-day outlook, a year of events. ## Guides - [Sunset forecast](https://asterfold.rork.app/sunset-forecast/) - [Golden hour today](https://asterfold.rork.app/golden-hour/) - [Stargazing forecast](https://asterfold.rork.app/stargazing-forecast/) - [Blue hour](https://asterfold.rork.app/blue-hour/) - [Moon phase tonight](https://asterfold.rork.app/moon-phase-tonight/) - [Meteor showers](https://asterfold.rork.app/meteor-showers/) ## FAQ - **What does Asterfold do?** Asterfold is a sunset field studio for iPhone and iPad with three connected parts. The Light Path Studio calculates the Sun's path, bearing, altitude, golden hour and blue hour for any place, saved viewpoint and date. The Viewpoint Planner saves the exact spots you watch from, with the direction you face, finds the dates when the Sun sets inside your view and plans sessions. The Field Journal records what each sunset really looked like and compares it with the forecast saved before the event. Tonight also rates the sunset, stars and sunrise from the cloud forecast. - **What is the Light Path Studio?** A sky dome showing the Sun's path for the day, coloured by golden hour, blue hour and twilight, with the year's sunset range on the rim. Drag through the day to read altitude, bearing and shadow length, or jump to the solstices. It is calculated on your device, works offline, and assumes a flat horizon, which it says on screen. - **How do viewpoints and alignments work?** Save a spot by GPS, town search or coordinates, then open Aim your view. Drag the first-person horizon left or right like turning your head, tap a sun line such as the year's most northerly sunset, or point your iPhone at the view and let the compass follow. Pick a lens (14 mm to 200 mm, or the phone's main camera) to set the frame width; green viewfinder corners and monthly sun dots show what will be in your shot as you aim. Asterfold lists the dates in the coming year when the Sun sets or rises inside that view, the next seven sunsets against your frame, and lets you plan a session with a light window, composition, gear, a reminder and a short checklist. Free keeps two viewpoints; Plus keeps unlimited. - **How is the sunset rating worked out?** Colorful sunsets need high or mid-level clouds to catch the light and a clear path for the light to reach them. Asterfold reads the forecast cloud layers (low, mid and high), fog and rain above you, and also the ordinary point forecast at two places 60 km and 180 km along the setting Sun's bearing, where low cloud can cut the light off. The app shows the reason with every rating. The rating is a rule-of-thumb score: it has not been validated against observed sunsets and is not a probability. - **What is the light path?** At sunset the Sun's light reaches your clouds almost sideways, after travelling a few hundred kilometres under them. Asterfold fetches MET Norway's standard point forecast at two places on that line, 60 km and 180 km toward the setting (or rising) Sun, and shows them next to your own spot as a cross-section. These are two samples of the forecast, not a model of every cloud along the line, and nearby hills or buildings aren't included. - **How does the Field Journal learn my sky?** After a sunset you rate what you saw in two taps and can add colours, clouds, the Sun, a note and an optional photo kept privately on your device. Each check-in is compared with the forecast saved before the event, never revised afterwards. After three check-ins nearby, ratings adjust for clear, high-cloud and cloudy evenings in small steps capped at 25 points, and once you have three at one viewpoint they use only that viewpoint. Sunsets you log elsewhere are kept as observation-only notes. - **Where does the forecast come from?** Cloud, rain and fog forecasts come from the Norwegian Meteorological Institute (MET Norway) and reach about nine days ahead. Sun, Moon and planet times are calculated on your device. - **Is Asterfold free?** Yes. The Light Path Studio, two viewpoints with alignments and plans, the Field Journal, check-ins and tuning, Tonight's ratings and light path, all the times, golden hour reminders, the next three evenings, 45 days of sky events and the Sky Log are free. Asterfold Plus adds unlimited viewpoints, smart alerts, the full 10-day outlook and a full year of events. - **Does it need an account or track me?** No account, no ads, no analytics. Viewpoints, plans, journal entries and kept photos stay on your device and are never uploaded. Only a position rounded to about 1 km is sent to MET Norway to fetch cloud forecasts. - **Does it work for stargazing?** Yes. The Stars rating combines forecast cloud during real darkness with moonlight, and the app shows the clearest stretch of the night and the moon-free hours. It doesn't include light pollution, so dark rural sites will do better than the number suggests. - **Is the rating a guarantee?** No. Forecasts change and local conditions vary. The ratings are an unvalidated rule-of-thumb estimate to help you decide when it's worth stepping outside; they are not a probability and their accuracy has not been measured. Data: MET Norway Locationforecast (CC BY 4.0). Place names: GeoNames (CC BY 4.0). Astronomy: Astronomy Engine via AstronomyKit (MIT).