The Pleiades, also known as the Seven Sisters and Messier 45, is a large open cluster and reflection nebula located in the constellation Taurus. Its brilliant blue glow is visible with the naked eye and has been documented all throughout history. So, how did I capture the Seven Sisters and what is it exactly?
The Pleiades shown in Stellarium
What is Messier 45?
The Pleiades is an open cluster and a reflection nebula. This means that there is a group of thousands of stars that were formed in the same massive molecular complex. These types of star clusters are usually younger and smaller than globular clusters because as they form, the stellar winds from stars push out the gas particles making up the complex, which stops star generation from occurring.
A reflection nebula is an area of dust illuminated by the bright stars behind it (In the case of the
Pleiades this is the open cluster). Usually the light that is reflected from a reflection nebula is blue, but in some rare cases, the nebula can be yellow or orange. The light emitted from such nebulae is actually photons from the star that bounce-or reflect-off of the dust particles in space. Usually that dust is very hard to see, but thanks to bright stars we can pick it up quite easily.
Rho Ophiuchi Cloud Complex: note the blue and yellow reflection nebulae (Credit: Galactic Hunter)
Early Observations
Even during ancient times Messier 45 grabbed the attention of the early astronomers. The Babylonians catalogued the cluster around 2200BC, the Ancient Egyptians most likely had common names for it, and the Pleiades even appears in Homer's The Odyssey dated to the 7th century BC. Further along, Galileo observed the cluster through a telescope he created. In the 1800s, Charles Messier recorded the object in his now famous catalogue. It is unknown who first took a photo of the Pleiades, but it was most likely captured in the 19th century. Today, Messier 45 is a very popular target to image by astrophotographers all around the world.
How did I capture the Pleiades?
Using a photography technique known as long exposure photography, I was able to collect nearly 3 hours of data on M45. With multiple 1.5 minute long exposures and 2 1/2 minute exposures, I was able to produce a photo with a great dynamic range with plenty of nebula detail. My total integration details are as follows:
Lights: 55 x 90s, 33 x 150s
Darks: 20 x 90s, 30 x 150s
Flats: 30
Biases: 50
My processing was quite simple. The steps are as follows:
SiriL: OSC_Preprocessing, Background extraction, Photometric color calibration, green noise removal
GIMP: Stretch, color balance, saturation, and final levels adjustments
After my processing, I produced this image. Please enjoy.
The Pleiades by Me
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