Clear-sky alerts
A note when tonight's clear, moonless window at your observing site is a few hours away. It comes by email, to your phone, into a Discord or Slack channel, onto your calendar, or to a device. It's the same plan the Observing Planner draws, so you don't have to keep checking it. By email or push you can also have a summary of the week on Sundays.
Your site
Choose a site to see tonight's plan.
Your rule
Clear is every hour of the window under your cloud limit, with fog under 25%, inside astronomical dark (the Sun 18° down). Clouds come from MET Norway's forecast (CC BY 4.0), adapted by CycleCalcs. One alert a night at most.
The Sunday summary comes after 3 pm at your site: the next seven nights' moonless dark, longest first, the windows that pass your rule on the nights the cloud forecast covers, and how the dark changes through the week. A week with no astronomical dark at your site gets none.
How to hear about it
We send one note to confirm, and nothing starts until you press its button.
Email alerts are not open yet. The calendar and the device feed below work now.
Phone, Discord or Slack
On a phone, install the free ntfy app, subscribe to a topic name only you know, and paste https://ntfy.sh/ followed by that name. For a Discord or Slack channel, paste the channel's webhook address. We send one test push with a link to confirm.
Push alerts are not open yet. The calendar and the device feed below work now.
Calendar
Each clear window that passes your rule becomes an event, with a reminder as far ahead as "Tell me" says. Subscribe to it so it keeps updating.
Choose a site first.Calendar apps refresh a subscription on their own schedule, from every few minutes to once a day. For a change the same evening, use email or push.
A device: Home Assistant, a roof script, a display
The feed answers whenever a device asks. go_tonight says whether tonight has a window that passes your rule, and next gives the first one ahead, with its start, end and minutes until it starts.
Choose a site first.A Home Assistant sensor, checked every 15 minutes:
Choose a site first.
A push to your own address arrives as JSON, signed. The CycleCalcs-Signature header is t=<unix seconds>,v1=<hex HMAC-SHA256 of t.body>, keyed with the signing key in the confirmation push.
How alert addresses are kept and deleted: the privacy policy.