The Pleiades – 9th Jan 2024
The Pleiades are the most prominent star cluster in the night sky. Also known as the Seven Sisters, they are located in the constellation of Taurus and are visible in the Northern Hemisphere from Autumn through to early Spring. Despite the name of the Seven Sisters, under light polluted skies most people can only make out 6 individual stars with the naked eye, however the cluster in fact contains about 1000 stars. In the image above, the Sisters are the brightest 4 stars that form a rectangle, plus the 3 slightly less bright stars above right of this rectangle. These stars are named after the 7 daughters of Pleione and Atlas (Sterope, Merope, Electra, Maia, Taygeta, Celaeno, and Alcyone), whilst Pleione and Atlas are the two stars to the left of the main group. The star cluster formed about 100 million years ago and is still dominated by hot, bright blue-white stars, however over time these bright stars will die out, leaving only the dimmer, longer lived stars. There is a lot of blue nebulosity around the stars which was at first assumed to be the remains of the gas cloud from which the stars were formed. However the bright stars would have long since dispersed this cloud, so it is likely that the group just happens to be passing through a cloud of gas and dust, and illuminating it with blue light from the hot stars. The cluster is located at a distance of 400 light years, and the central group of brightest stars is about 8 light years across.
The Pleiades are one of the most popular targets for Astro-Photography as they are easy to find, very bright and contain some interest in the nebulosity surrounding the stars. However they do present a challenge to photograph and process well, as trying to capture the faint nebulosity can easily lead to over-exposed stars. The image above was taken at a fairly dark sky sight in Wales using a portable rig consisting of a standard camera and lens, mounted on a small tracker. I have used a relatively short exposure time of 60sec to avoid star trails and prevent over-exposing the stars, but have then shot for 4 hours total exposure time. As the tracking is not perfect, the Pleiades drifted slightly over the 4 hours. After stacking this resulted in some ‘walking noise’ – coloured streaks due to the fixed patter noise of the sensor moving across the image. A lot of processing in Pixinsight and Photoshop was needed to minimise this effect.
Image Details
- Date: 9th Jan 2024
- Exposure Details: 240 x 60s, F5.6, ISO400
- Total Integration Time: 4hr
- Camera: Canon EOS-R (unmodified)
- Telescope: Canon 300mm F4L Lens + 1.4 TC at 420mm focal length.
- Mount: iOptron SkyGuider
- Processing: Stacked in DSS, Processed in Pixinsight, Finished in Phgotoshop