More than astrophotography, an astronomical exploration.
M25 in a sea of golden stars
David Cruz · Astromidnight
In Sagittarius, towards the central regions of the Milky Way, the cluster M25 seems to float in a sea of golden stars. Among its blue stars pulses U Sgr, a yellow supergiant that changes brightness every 6.75 days.
| Catalogue | Messier 25 · IC 4725 |
| Type | Open cluster |
| Distance | ≈ 2,100 light-years |
| Field | 84.3′ × 56.2′ |
| Real width | ≈ 52 × 34 light-years |
| Scale | 1.01″ / pixel |
| Orientation | −3° · north up |
| RA (centre) | 18h 31m 47s |
| DEC (centre) | −19° 06′ 58″ |
| Constellation | Sagittarius |
| Objects in field | M25 · U Sgr · 2 planetary nebulae |
Distance and age of M25 from the Gaia catalogue of Hunt & Reffert (2023); the catalogue of Cantat-Gaudin et al. (2020) gives ≈ 2,300 light-years. The real width assumes the distance of the cluster; the foreground stars and the planetary nebulae are at other distances. The distances of the two planetary nebulae are not well measured. Positions from AstroBin or SIMBAD; those of the nebulae are approximate.
7 h 20 min of light
Each tick is a 240-second exposure. 110 in total, with the camera at −10 °C and gain 100. Calibrated with 30 darks, 30 flats and 30 bias. The Moon stayed below 5 % illumination throughout.
Carbon Newton 10' f/4
ZWO ASI2600MC Pro
Twinstar Friction Mount FG80
Askar M54 OAG · ZWO ASI120MM Mini
TS-Optics Maxfield .95X Coma Corrector
Adobe Photoshop · Pleiades Astrophoto PixInsight · Stefan Berg Nighttime Imaging 'N' Astronomy (N.I.N.A. / NINA)
São Pedro da Gafanhoeira, Évora · 358 m
Bortle 3