M13

Data Sources

Deep sky object data is compiled from authoritative astronomical catalogs including NGC (New General Catalogue), IC (Index Catalogue), Messier, and Caldwell. Primary source: OpenNGC.

Coordinate Systems

Right Ascension (RA): Celestial longitude measured in hours, minutes, and seconds (0h to 24h).

Declination (Dec): Celestial latitude measured in degrees, arcminutes, and arcseconds (-90 to +90 degrees).

Magnitude Scale

The astronomical magnitude scale is logarithmic. Lower values = brighter objects. The formula relating magnitude difference to brightness ratio:

\[m_1 - m_2 = -2.5 \times \log_{10}\left(\frac{F_1}{F_2}\right)\]

where m is magnitude and F is flux.

Observing Recommendations

Recommendations are calculated based on:

• ความสูง: Objects above 30 degrees altitude are easier to observe
• โชติมาตร: Brighter objects (lower magnitude) are easier to see
• Moon Phase: Dark skies (new moon) improve visibility of faint objects

Rise and Set Times

Calculated using Skyfield astronomical library with observer's location and date. Times shown in local timezone. Objects are considered visible when altitude is above 0 degrees.

Best Viewing Time

Determined by finding when the object reaches maximum altitude (culmination) during nighttime hours. Calculated as:

\[t_{\text{best}} = \arg\max_{t \in \text{night}} h(t)\]

where h(t) is altitude as a function of time.