Andromeda Galaxy
About this image
## M31 – The Andromeda Galaxy
M31, better known as the Andromeda Galaxy, is one of the most famous deep-sky objects in the night sky. Sitting around 2.5 million light-years away, it is the closest large spiral galaxy to our own Milky Way and is heading slowly in our direction. In several billion years, the two galaxies are expected to merge.
This image shows the bright central core of Andromeda, surrounded by sweeping dust lanes and the softer outer glow of billions of stars. Although M31 is usually treated as a broadband target, I used the Optolong L-eNhance filter to help bring out the hydrogen-alpha regions within the galaxy.
These H-alpha regions are areas of active star formation, where clouds of hydrogen gas glow as young, hot stars energise the surrounding nebulae. They appear as subtle reddish-pink knots and patches across the spiral arms. Using the L-eNhance helped isolate this signal and gave the image more depth, revealing that Andromeda is not just a smooth galaxy, but a living structure full of dust, gas, and new stars being born.
Capturing M31 is always impressive because of its sheer size. It spans several times the width of the full Moon in the sky, making it one of the largest deep-sky objects visible from Earth. Even from light-polluted skies, it remains a rewarding target and a reminder that we are looking far beyond our own galaxy.
Annotated image
Image details
| Object type | galaxy |
|---|---|
| Catalogue | M31, NGC 224, PGC 2557, M 31 – NGC 224 – PGC 2557 – UGC 454 |
| Constellation | Andromeda (And) |
| Observed | 2025 Sept 21 – 20:33 UTC |
| Location | Portsmouth, UK |
| Moon | Waning Crescent – 24% illuminated – age 24.7 days |
| WordPress categories | Galaxies |
Equipment
| Telescope | William Optics RedCat 51 |
|---|---|
| Camera | ZWO ASI2600MC Pro |
| Mount | AM5 / Juwei 17 |
| Filter | Optolong L-eNhance |
| Focal length | 250mm |
| F-ratio | f/4.9 |
| Pixel scale | 3.1 arcsec/pixel |
Acquisition
| Exposure | 155 x 180s subs with a broadband filter 40 x 180s subs using the Optolong L-eNhance |
|---|---|
| Gain | 100 |
| Guiding RMS | <1.5 |
Observation notes
21–22 September 2025
Finally had a clear window to give M31 a proper shot using my Redcat 51mm on the AZ-GTi in EQ mode. Captured:
155 x 180s subs with a broadband filter
40 x 180s subs using the Optolong L-eNhance
Processing notes
All stacked in Astro Pixel Processor, processed in PixInsight.
Posted from CityAstroLog.