Astronomy tools that help you observe, compare and understand the sky
Plan an observing session, find useful deep-sky targets, compare telescope equipment, check imaging scale and understand the astronomical coordinates and measurements behind the result.
- Observation planning
- Telescope and eyepiece comparisons
- Deep-sky target reference
- Astrophotography setup analysis
Choose the night, the target and the equipment in one connected workflow
Each major experience leads naturally to the next task, from checking darkness to choosing a target and deciding whether an eyepiece or camera setup suits it.
Night Observation Planner
Estimate sunset, civil, nautical and astronomical twilight, the available dark window, Moon illumination and approximate planetary visibility for a chosen location and date.
Plan a night →Target referenceDeep-Sky Object Explorer
Filter prominent Messier targets by object type, season, constellation, visual magnitude and angular size before choosing what to observe.
Find a target →Telescope opticsTelescope Setup Calculator
Calculate magnification, exit pupil, focal ratio, field of view and theoretical resolution together rather than judging a setup by power alone.
Check a setup →Move from sky conditions to framing and imaging decisions
The tools share the same concepts and reference data so a result can lead directly to the next useful calculation.
Moon Observing Planner
Interpret lunar phase and illumination for lunar detail and deep-sky contrast.
Open tool →ToolEyepiece Comparison
Compare up to four eyepieces on the same telescope using magnification, exit pupil and true field.
Open tool →ToolField of View Simulator
See how familiar targets fit within an estimated eyepiece field.
Open tool →ToolPixel Scale and Sampling
Match pixel size, focal length, sensor dimensions and seeing before an imaging session.
Open tool →ToolRA/Dec to Alt/Az
Turn catalogue coordinates into a local sky position for your location and time.
Open tool →ToolPlanet Comparison
Compare size, mass, density, gravity, day length, year length and escape velocity.
Open tool →Use detailed guides when a number needs physical or observational context
Read about celestial coordinates, twilight, Moon phases, atmospheric seeing, transparency, telescope field of view, pixel scale and astronomical distance, then apply the explanation directly in the related tool.