Pocket Astronomer
Flagship GPS Large Horizon Edition
Copyright 2026 © Astrophyzix.org
Alt ° Az °
RA
Dec
| Planet | Alt ° | Az ° | Mag | Dist AU |
|---|
Last Maintenance: 01 April 2026
1. Description
Pocket Astronomer GPS is a live, browser-based ephemeris engine designed to run inside Astrophyzix Digital Observatory. It computes real-time positions of the Sun, Moon, and five naked-eye planets using peer‑reviewed astronomical algorithms. All calculations run client-side with no servers or APIs.
Key Features
- Real-time animated sky dome with stars, planets, Sun, and Moon
- Local Sidereal Time clock
- Sun: RA/Dec, alt/az, distance, angular diameter, rise/set/transit, twilight times
- Moon: RA/Dec, alt/az, distance, phase, illumination, libration, parallax, rise/set/transit
- Five planets: geocentric RA/Dec, alt/az, distance, magnitude, angular separations
- 55-star catalogue with spectral colour coding
- Horizon panorama with altitude grid and object labels
- Sky quality metrics (NELM, SQM estimate, Milky Way visibility)
- GPS, city presets, or manual location entry with localStorage persistence
- Fully static, zero server-side dependencies
Intended Audience
- Amateur astronomers
- Astronomy educators
- Bloggers and web publishers
- Students of observational astronomy
- Anyone wanting to know what is visible in the sky right now
Note: Not a replacement for professional ephemeris tools such as JPL Horizons.
2. Location Settings
Setting Observer Location
Method A -- GPS (Recommended)
- Tap the location name under the sidereal clock.
- Tap GPS Locate and grant permission.
- Tap Apply.
Method B -- City Preset
- Open location panel, choose a preset city, Apply.
Method C -- Manual Entry
- Enter latitude/longitude manually, Apply.
Persistence: Location is saved in localStorage.
3. Browser Support & Permissions
Browser Compatibility
| Browser | Version | Status | Notes |
|---|---|---|---|
| Chrome (Android) | 90+ | Supported | Recommended |
| Firefox (Android) | 88+ | Supported | -- |
| Safari (iOS) | 14+ | Supported | GPS requires HTTPS |
| Chrome (Desktop) | 90+ | Supported | Full features |
| Firefox (Desktop) | 88+ | Supported | -- |
| Edge | 90+ | Supported | -- |
| Internet Explorer | Any | Not Supported | No Canvas API |
| DuckDuckGo | Any | Supported* | GPS may be blocked |
*Defaults to London if GPS is blocked.
Required Permissions
- Geolocation: Only for GPS mode.
- localStorage: Saves observer location.
- Network: Only for Google Fonts.
4. Sky Dome & Controls
The sky dome is an azimuthal equidistant projection with zenith at centre and horizon at rim.
Overlay Controls
- Const. -- Constellation lines
- Planets -- Planet glyphs and halos
- Grid -- Equatorial grid
- Labels -- Bright star labels
Tap / Click Interaction
Tap any object to view tooltip with RA/Dec, alt/az, distance, magnitude, etc.
Star Colour Guide
| Class | Colour | Temperature | Example |
|---|---|---|---|
| O | Blue-violet | > 30,000 K | Naos |
| B | Blue-white | 10,000-30,000 K | Rigel |
| A | White | 7,500-10,000 K | Sirius |
| F | Yellow-white | 6,000-7,500 K | Procyon |
| G | Yellow | 5,200-6,000 K | Capella |
| K | Orange | 3,700-5,200 K | Arcturus |
| M | Red-orange | < 3,700 K | Betelgeuse |
5. Tabs Overview
Overview Tab
- UTC Date/Time
- Julian Date
- Sun Altitude & Sky State
- Moon Altitude & Phase
- Celestial Horizon panorama
- Visible Stars count
- Planets Up
Sun Tab
- RA/Dec
- Altitude/Azimuth
- Distance & Angular Diameter
- Twilight Bar
- Sunrise/Transit/Sunset
- Civil/Nautical/Astro dawn & dusk
- Day Length & Solar Noon
Moon Tab
- Rendered lunar disc
- Phase name & illumination
- Age in days
- Distance & Angular Diameter
- Libration Lat/Lon
- Parallax
- Moonrise/Transit/Moonset
Planets Tab
- Altitude & Azimuth
- Magnitude
- Distance (AU)
- Angular separations
Sky Quality Tab
- NELM
- SQM estimate
- Milky Way visibility
- Zenith star
- Magnitude scale
- Brightest Visible
- Rising Soon
6. Computational Methods
Accuracy Summary
Sun & Moon: < 0.01 deg; Planets: 0.1-1.5 deg depending on body; Stars: < 0.001 deg.
Limitations
- Not suitable for precision astrometry or occultation prediction
- No nutation (limits accuracy to ~0.01 deg)
- No annual aberration for planets
- No atmospheric refraction in displayed altitudes
- Uranus/Neptune/Pluto not computed
Algorithms
- Sun: Meeus Ch.25 low-precision
- Moon: 30-term ELP series
- Planets: VSOP87 truncated mean elements
- Rise/Set: Meeus Ch.15 with bisection refinement
- Equatorial to Horizontal: Standard spherical trig
- Twilight: Solar depression angles (-6, -12, -18 deg)
Built upon MIT framework | Copying, Embedding, Iframe embedding, redistribution or selling of this software is strictly forbidden without consent of Astrophyzix Digital Observatory | Copyright © 2026 Astrophyzix.org
"It's a neat little thing. No it's not sky safari or stellarium, but that isn't it purpose. Its a quick shot of what you can basically see in your immediate area naked eye. I could see this having some use for nights when you are basically going out for a quick look."