Active equipment
150 mm reflector
Reflector · Manual
150 mmAperture
750 mmFocal length
f/5.0Focal ratio
25 / 10 / 6 mm eyepieces · 60° apparent field
MAKE IT YOUR OBSERVATORY
Equipment & locations
Your instruments, observing spots and real-world horizon.
Your equipment
10 × 50 binoculars
Binoculars · Manual
50 mmAperture
200 mmFocal length
f/4.0Focal ratio
10× fixed power
Naked eye
Naked eye · Manual
7 mmAperture
17 mmFocal length
f/2.4Focal ratio
17 mm eyepieces · 60° apparent field
Starter instruments are editable examples, not a claim about equipment you own. Each eyepiece can have its own apparent field. Camera sensors and exposure planning are not included.
Saved observing locations
6
Manual estimate. No light-pollution map is connected, and Bortle class is not inferred from your coordinates.
Your local horizon
Edit horizon · Geneva
Enter your own estimates. Points form a continuous skyline; walls cover a range of bearings. These are not measured terrain data.
North 0° · East 90° · South 180° · West 270°. A wall from 330° to 30° crosses north. Resetting affects only this location.
Changes apply when saved.Compare a night away
Your active spot compared with another saved location.
Add a second location to compare your home sky with a dark-sky spot.
Compares calculated sky geometry, Bortle and your horizon for the selected date. Forecasts are not included in this location comparison.
Display preferences
Advanced astronomy data
Show precise coordinates and more optical detail.
Display units
Telescope focal lengths stay in millimetres.
Observing preferences & local data
Red light / night vision mode
Show objects as seen visually
20°
250×
The altitude preference filters recommendations. Seeing limits guide equipment suggestions. Visual mode sets the simulator and detailed observing tools. Air quality and visual contrast remain estimates.
Your equipment, locations, horizon and journal are saved in this browser. Export a backup to transfer them to another device or recover them after clearing browser data.
DATA, SAFETY & LIMITATIONS
Clear about what we know
Calculated astronomy
Solar System positions, phases, twilight and eclipse events use Astronomy Engine (MIT). Fixed objects use rounded J2000 coordinates with precession and nutation to the selected date. Fixed-target events are sampled; proper motion is omitted.
Catalogue reference: OpenNGC (CC BY-SA 4.0). This is a curated bright-target subset, not a complete catalogue.
Weather & places
Open-Meteo provides cloud, temperature and wind forecasts; GeoNames via Open-Meteo provides city search. Forecasts are not observations or astronomical-seeing predictions. No forecast is substituted when the provider is unavailable.
No automatic Bortle measurement is supplied. Weather may be unavailable outside the forecast period.
Reference imagery
Saturn: NASA/JPL/Space Science Institute. M31: NASA, ESA, B. Williams, Z. Chen, L. Clifton Johnson; image processing J. DePasquale (STScI). Moon: NASA.
These are labelled reference photographs, not visual telescope predictions. NASA media guidelines; no endorsement implied.
Honest visual expectations
Eyepiece field and angular scale are calculated. Texture, simulated star fields, contrast and brightness are educational approximations. The Moon is not a crater atlas; no current sunspot map, Jupiter weather, Great Red Spot transit or individual planetary moon events are claimed.
Comet/asteroid feeds, satellites, retrograde stations, accounts, French translation and camera planning are future integrations. Interface text is isolated from astronomy logic for localisation.
AAS solar safety: a certified, manufacturer-approved visual solar filter must be secured over the front aperture before aiming ordinary optics at the Sun. Eclipse glasses must never be used behind unfiltered optics.
Equipment, locations, settings and observations are saved to your browser on this device. Coordinates are sent directly to Open-Meteo when requesting weather; place searches are sent to its geocoding service. Nothing is posted publicly. Save failures are shown; changes remain on the current page for retry.