For night-sky observing

See whether tonight is worth going out

Noctar puts weather, sky darkness, the Moon and the aurora in one view. You get a night rating for a place you choose, and a signal when the forecast nears the conditions you set.

Check tonightCreate an account for alerts

Weather comes from Open-Meteo, the Kp forecast from GFZ Potsdam, and live aurora data from NOAA. These are indices and a forecast, not a promise of clear sky.

Sample data

74

0–100

  • Clouds 18%
  • Seeing 1.4″
  • Kp 4

Astro Score 74

What you get before you pack the gear

One place instead of stitching forecasts together at midnight.

  • One rating for the night

    Astro Score folds the Moon, seeing, dew, clouds and the astronomical window into a score from 0 to 100.

    Night rating

  • You see what would spoil the trip

    Clouds, unsteady air, dew on the optics or a bright Moon show up before you drive.

    Weather for observing

  • Aurora without refreshing charts

    The Kp forecast, live Bz and solar wind, and a local probability sit side by side.

    Aurora

  • A signal when a window is near

    An account can email you about the next good window. Custom thresholds and webhooks are Premium.

    Email alerts

  • Place and direction

    The planner shows Sun and Moon azimuths. The sky map shows what is above the horizon.

    Sky and plan

  • More than one evening

    The hourly table for 7 nights is Premium, when a trip cannot depend on a single night.

    What is immediate, and what is Premium

How it works

Three steps. The rest can happen without refreshing cards.

  1. 1

    Pick a place

    GPS, a point on the map, or a saved location. The forecast and time zone follow that point.

  2. 2

    Read the night

    The dashboard shows Astro Score, weather, seeing, dew, the Moon and the aurora for that site.

  3. 3

    Choose what should reach you

    An email about a good window needs an account. Premium adds your own conditions and a webhook.

Night rating

You get a verdict, not just the temperature

A normal forecast says whether it will rain. It does not say whether the sky will be dark, steady and dry on the glass.

Noctar builds Astro Score from the Moon, seeing and dew point. Clouds and the astronomical window act as a gate. Transparency and the cloud trend for the next hours sit beside it.

  • Astro Score 0–100 and a verdict for tonight
  • Seeing in arcseconds, with Antoniadi and Pickering scales
  • Dew point and the risk of moisture on the gear
  • Transparency and the cloud trend for about 18 hours
  • Astronomical-night hours, including white nights

Example. In the evening Astro Score drops because high cloud arrives after midnight, even though the temperature looks calm. You stay home instead of driving an hour.

The score is a model of conditions, not a measurement of your sky. When data is missing, the card shows a gap instead of an invented number.

Open the dashboard
Example
  • Astro Score74
  • Seeing1.4″
  • Dew+6°

Weather for observing

You watch the values that ruin a frame

Wind, humidity and low cloud decide a session more often than a sun icon.

The weather card uses the Open-Meteo forecast for your point: total cloud and layers, wind, gusts, humidity, visibility, precipitation, pressure and temperature.

  • Total cloud plus low, mid and high layers
  • Wind, gusts and direction
  • Humidity, visibility and chance of rain
  • Air temperature and feels-like temperature
  • °C or °F, and 24-hour or 12-hour time

Example. Total cloud looks low, but the low layer still sits on the horizon. You know the west is not clear yet.

This is a model forecast. If the provider omits a layer, the field stays empty.

Example
  • Clouds18%
  • Wind12 km/h
  • Visibility24 km

Aurora

You see when the chances rise - not when the aurora is certain

Kp on one site and clouds on another drift apart in time. It is easy to go out too late, or under a full overcast.

Noctar puts the Kp forecast (GFZ), live Bz, solar-wind speed and density (NOAA) and the local Ovation probability together. The planner can lay the same aurora model on the map.

  • Kp forecast, plus min/max when the data includes them
  • Live Bz, solar-wind speed and density
  • Local probability for your coordinates
  • SWPC forecast images and the HUXt preview when the source responds
  • An alert when Kp or other thresholds meet your rule (Premium)

Example. Kp rises to 5, Bz turns negative, and cloud over your town is low. You get a signal that it is worth looking north - if the sky is actually clear.

An alert and a probability do not guarantee an aurora. Latitude, clouds, lights and the forecast itself still decide. Negative Bz favours aurora; it does not promise it.

See aurora on the dashboard
Example
  • Kp4
  • Bz−4 nT
  • Chance12%

Sky and plan

You decide where to stand and which way to look

Weather alone does not say when the Moon enters the frame or where the Milky Way is.

The Sun and Moon have their own cards: rise, set, twilight and altitude. The planner draws azimuths on a map. The sky map shows stars, planets and deep-sky objects for your time.

  • Twilight, sunrise, sunset and altitude
  • Moon phase, illumination and altitude
  • Planner: pin, target and azimuths, with an aurora layer
  • Sky map with stars, planets and deep-sky objects
  • Two nearest photo targets for free; the full list, ISS transits with GPS and the occultation calendar are Premium

Example. Before you leave you see that moonrise is after midnight, and the planner shows which way to frame the shot at 22:30.

Sun and Moon positions are calculated locally. The aurora map is a NOAA model, not a photograph of the event.

Open the planner
Example
  • Twilight21:12
  • Moon38%
  • Azimuth248°

Email alerts

Noctar speaks up when a window is close

Checking every hour by hand ends with a missed gap in the cloud.

With an account you can turn on an email about the next good observing window. The free plan covers one alert location. Premium adds custom rules and up to five places.

  • Email about the next good window in astronomical night
  • One location on the free plan
  • Custom rules: Astro Score, clouds, wind, Kp and other thresholds (Premium)
  • Up to five notification locations on Premium
  • Unsubscribe from the email itself

Example. You ask for a message when Astro Score and cloud cover enter your range in the coming hours. You stop refreshing the dashboard from work.

The email describes a forecast, not a confirmed event. Sending is spaced so it does not flood the inbox. Custom rules need Premium.

Go to alerts
Example
  • Window22:40
  • Threshold70
  • Place1

Webhooks

Your system reacts when conditions cross a line

Discord, home automation or a club script still waits for someone to paste the forecast.

Premium can POST JSON to your URL when a good window appears, a rule matches, or a daily summary is due. The payload can be signed. The condition catalog matches the alerts.

  • Events: good window, rule, daily summary, or a snapshot every 15 minutes, hour, or custom interval
  • Conditions for weather, seeing, the Moon, the Sun and Kp
  • Match now, or look ahead 24 hours
  • Discord, Slack, Home Assistant or your own URL
  • Field selection and an HMAC signature

Example. When Kp is at least 5 and cloud falls under your threshold, Noctar posts to the club channel. Nobody has to watch the chart.

Webhooks are Premium. A missing forecast value does not match a condition. Live Bz and solar-wind speed are not hourly webhook rules - they stay on the aurora card.

Set up a webhook
Example
  • Eventalert
  • Kp≥ 5
  • Clouds< 30%

How this differs from checking a forecast yourself

No competitor names. The difference is how many decisions stay on you.

  • Several sources at once

    Kp on one site, clouds on another, the Moon on a third. It is easy to compare a different hour and a different town.

  • A normal weather forecast

    It is good at rain and temperature. It does not build an astronomical window, seeing, or an aurora chance for your point.

  • Noctar

    It combines those signals for a chosen location and can send an email or webhook when the forecast enters your thresholds.

Who Noctar is for

Each group gets a different reason to come back.

  • Aurora watchers

    They see the Kp forecast, the live solar wind and a local probability before they head north.

  • Astrophotographers

    They check whether seeing, clouds, dew and the Moon allow a session at a specific site.

  • People planning a night outside

    They know when darkness starts and whether the sky over a chosen point is likely to clear.

  • Clubs and custom integrations

    On Premium they pass conditions to Discord, Slack, Home Assistant or their own system.

What is immediate, and what is Premium

You can use the dashboard, planner and sky map in the browser without an account. Alerts need an account. Prices live on the plans page - they are not repeated here.

No charge

Dashboard, planner, sky map, Sun, Moon, aurora and weather. A free account: email about a good window for one location, and a short photo-target list.

Premium

7-night table, best-window search, ranking of saved places, custom alert rules, up to five notification locations, webhooks, the fuller target list, ISS transits with GPS and the occultation calendar.

See plans

Questions that come up before the first night out

What is Noctar?

A browser app for planning night-sky observing. It shows conditions for a place you choose and can alert you when the forecast meets your criteria.

Which alerts does Noctar support?

An account can receive an email about the next good window. Premium adds custom rules (for example clouds, seeing, Kp) and webhooks to other systems.

How does aurora information work?

Noctar shows the Kp forecast, live Bz and solar wind, and a probability for your coordinates. An alert rule can use a Kp threshold. Live Bz is not an hourly webhook rule.

Does an alert guarantee I will see the aurora?

No. An alert means a forecast or index crossed a threshold. The aurora may not happen, clouds may hide it, or it may be too faint at your latitude.

Which locations can I watch?

Any point from GPS, the map or a saved list. The forecast and time zone follow those coordinates. Email alerts: one location for free, up to five on Premium.

What are Astro Score and seeing?

Astro Score is a combined night-quality rating from 0 to 100. Seeing describes air stability in arcseconds: lower means a steadier image. Both come from a forecast and calculations, not a sensor in your garden.

How do webhooks work?

On Premium, Noctar sends JSON to a URL you provide when a chosen event happens: a good window, a matched rule, a daily summary or a periodic snapshot. You can choose fields and sign the body.

Can I set my own thresholds?

Yes, in Premium rules. You compare a value (for example cloud, wind, Astro Score, Kp) with a threshold. The free plan uses the ready-made good-window alert for one location.

How do I start?

Open the dashboard, pick a place and read the night rating. An account is needed for email, saving settings on the server, and Premium features.

Does Noctar cost money?

The basic condition view is free. Premium unlocks the 7-night table, custom alerts and webhooks, among other tools. Current prices are on the plans page, and Stripe handles payment.

Start with the place you want to watch

The dashboard works immediately. Alerts and automation wait until the account is ready.

Check tonightCreate an account for alerts