Observer Tools
- 🔭 Track your equipment & rigs
- ⚙️ Calculate FOV, f-ratio, image scale
- 📍 Save & share dark sky sites
- 📝 Observation notes
- ⭐ Favourite celestial objects
Rig Selector
Select a rig to calculate its optical properties. Add rigs in Settings → Rigs.
Sensor Diagnostics — Dust Spot Analyzer
Upload a flat frame (or any evenly lit image) to detect dust spots on your optical train. The analyzer measures each spot's pixel diameter and uses your rig's focal ratio to estimate how far from the sensor the dust is located.
Sign in to use the Dust Spot Analyzer
The analyzer uses your rig's focal ratio to calculate dust distances. Save a rig first, then upload your flat frames here.
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Astronomical Distance Converter
Convert between terrestrial and astronomical distance units.
All units
Physical Constants
Fundamental constants used in astronomy and astrophysics. Click a value to copy it to the clipboard.
Drag to rotate · Scroll to zoom · Click a star · Double-click cardinal to snap · Toggle polar/zenith view
How well do you know the night sky?
6 questions · Multiple choice · Instant explanations
Create a free account to save your progress and track your level.
How do levels work? ▾
Master questions by answering them correctly 2 times across separate sessions. Wrong answers reset your streak. Mastered questions retire from your active pool, so the quiz stays fresh and challenging.
Leveling up is based on total mastered questions, but each difficulty has a cap on how much it contributes — so you can't level up on Easy questions alone. Hard questions always count fully.
| Level | Title | Total Needed | Easy counts up to | Medium counts up to | Hard counts up to |
|---|---|---|---|---|---|
| 1 | ✦ Stargazer | — | — | — | — |
| 2 | ✦ Observer | 20 | 20 | 20 | ∞ |
| 3 | ✦ Amateur | 45 | 30 | 35 | ∞ |
| 4 | ✦ Astronomer | 80 | 30 | 50 | ∞ |
| 5 | ✦ Deep Sky Hunter | 120 | 30 | 65 | ∞ |
| 6 | ✦ Expert | 165 | 30 | 65 | ∞ |
Constellation Drill
Practice identifying all 88 constellations. Options change every session.