NGC 7331 (Pegasus)
The unbarred spiral galaxy NGC 7331 (Caldwell 30) in the constellation Pegasus
Fig. 1 - The bulge of the galaxy rotating in the opposite sense to the disk: The spiral galaxy NGC 7331 in Pegasus, photographed with an 8-inch f/5 Newtonian reflector on a ZWO AM5 mount.
| Object name: | Constellation: | Coordinates: | Apparent size: | Visual brightness: |
|---|---|---|---|---|
| NGC 7331 | Pegasus | 22h37m / +34°25' | 10.5' x 3.7' | 9.5 mag |
NGC 7331 (Caldwell 30) is an unbarred spiral galaxy in the constellation Pegasus. It appears similar in size and structure to the Milky Way, and is sometimes referred to as 'the Milky Way's twin'. However, the Milky-Way is believed to be a barred spiral, compared to the unbarred status of NGC 7331. In spiral galaxies the central bulge typically co-rotates with the disk but the bulge in the galaxy NGC 7331 is rotating in the opposite direction to the rest of the disk.
NGC 7331 measures 140,000 light-years in diameter and is 44 million light-years from Earth. It was discovered by German-born British astronomer and composer William Herschel in 1784 (source: Wikipedia).
Technical Details:
Exposure time: 6h 30min (130x3min)
Gain: 100
Temperature: -10°C
Date: September 27/28 and September 29/30, 2025
Processing: Astro Pixel Processor (APP) and Photoshop
Calibration: Darks, flats, and bias
Equipment:
Cooled ASI 2600MC Pro camera, TeleVue Paracorr Type II coma corrector, 8" f/5 "ONTC" Newtonian telescope, ZWO AM5 Strain Wave Mount, ZWO OAG-L off-axis system, ASI 174MM Mini guide camera, ASIAIR Plus
NGC 7331 was also captured with a 16-inch dobsonian on an equatorial platform. The image can be seen here.
Fig. 2 - Larger image version with labels (click on image).
Fig. 3 - Search chart for NGC 7331. Copyright 2025 'The Mag-7 Star Atlas Project', www.siaris.net.