I'm a beginner in Astronomy. What do these latitudinal and longitudinal lines and accompanying hours and degrees represent (in blue: +12h , +11h.. and +45° +60°.. , in orange: +330° , +15°) ?
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1$\begingroup$ Where does that image come from? When you post other people's work here, you need to give proper attribution. $\endgroup$– PM 2RingJun 24, 2021 at 21:11
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2$\begingroup$ Here's a hint; the 315° line goes straight down from overhead to the horizon where it is labeled as "NW" which represents the cardinal direction North-West which is of course at the 315° position. The two stars in Ursa Major (the Big Dipper) that run parallel to the blue "11 h" line are known to be an easy way to find the North Star; a line following those two stars towards the open end of the dipper will lead you to it. $\endgroup$– uhohJun 25, 2021 at 4:04
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1$\begingroup$ @uhoh thank you, really helpful $\endgroup$– huabJun 26, 2021 at 22:20
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The blue grid shows equatorial coordinates: right ascension (0h..24h) and declination (-90°..+90°). Declination is 0° on the celestial equator and ±90° at the celestial poles. The Sun's right ascension is 0h at the March equinox, 6h at the June solstice, etc.
The orange grid shows horizontal coordinates: altitude (-90°..+90°) and azimuth (0°..360°). Altitude is 0° on the horizon and +90° at the zenith. Geographic north is azimuth 0°, east is azimuth 90°, etc.
