Mis à jour : 22 mai 2020
Messier 4 is a beautiful globular cluster located in Scorpius, very close to the bright orange star Antares. The unique aspect of photographing M4 wide field is that you can see all the nebulous gas lit up by Antares all around the bright star. This gas is part of the Rho Ophiuchi molecular cloud complex in Ophiuchus/Scorpius.
We imaged this target for just a little over 1 hour as it was just rising above the mountains. We did not have any other target we wanted to photograph with the wide telescope while waiting for large nebulae to rise around 1AM. We usually never image objects that are below 25 degrees in altitude, but we had a "screw it" moment and decided to take the risk. Obviously, the quality of the final image is not really good and the gases really lack colors. The cluster does look fine though.
M4 is best photographed in Summer. Read our guide on the 15 best Astrophotography targets for Summer if you need some inspiration about what to image next!
Messier 4, Antares, and surrounding Nebulosity
Camera: ZWO ASI 1600MC
Telescope: Meade 70mm APO
Mount: Atlas EQ-G motorized Mount
Guiding: ZWO ASI 290MM Mini
Acquisition: ZWO ASIAIR
Total Exposure Time: 1 hour and 15 minutes
Exposure Time per frame: 30 seconds
Filters: L, R, G, B
A crop on the bright orange star Antares. Antares is very easy to spot in the night sky and is sometimes even confused for Mars due to its vivid orange glow!
In photography, Antares is surrounded by nebulous gas part of the Rho Ophiuchi molecular cloud complex. Some of this gas can be seen on the picture on the left.
Much more of this gas would be visible to the right if the framing of our image was different!
And here is a crop on the cluster we wanted to capture: Messier 4.
This is a bright and large globular cluster that fits easily in the same field of view as Antares if using a wide telescope.
M4 was the first cluster where individual stars were resolved! It was discovered in 1745 by Chéseaux, and added to Messier's catalogue in 1764.
How to find M4?
Because of its close proximity to Antares, M4 is very easy to find in the night sky! Late in Spring or anytime in Summer, wait for the Scorpion's tail to rise in the horizon. Look for the brightest star, Antares. Make sure you are actually looking at this star and not Mars which has the same color and can be near the same path as Antares from time to time.
The globular cluster M4 can be found just near Antares. Pointing your telescope at the bright star will most likely show you the cluster in there as well. Note though that another, smaller and fainter globular cluster is visible even closer to Antares, but it is not a Messier object!
We wish we imaged Messier 4 while it was higher in the sky and spent more time on it, but that will be for another time! We're glad we are still proud enough of the cluster itself to add it to our catalogue and will have all the time in the world to revisit it in the future.
Antoine & Dalia Grelin
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