Exposure: 21x300" @ ISO 800
Telescope: William Optics Megrez 88FD with Borg DG-L
Filter: Hutech IDAS LPS 2"
Mount: Skywatcher EQ6 Pro
Camera: Modded Canon 350D in cooler box
Date: 21th June 2009
Location: Coll d'Ares, Àger
Comments: I had to make a difficult decission about what features to leave out of the framing, this area of the sky is very beatiful and plenty of interestin objects and it's better imaged doing a mosaic or with a shorter focal.
Antares, at the top left corner, is a class M supergiant star, with a radius of approximately 800 times that of the sun; if it were placed in the center of our solar system, its outer surface would lie between the orbits of Mars and Jupiter. Antares is approximately 600 light-years from our solar system in the constellation Scorpius. The mass of the star is calculated to be 15 to 18 solar masses so it has a very low average density. The yellow nebulosity surrounding Antares to the right is reflecting the yellow light emitted by the star.
M4, at the bottom left corner, is a rather loosely concentrated cluster of class IX and measures 75 light-years across. M4 is approximately 7200 light years away, the same distance as NGC 6397, making these the two closest globular clusters to our Solar System. It has an estimated age of 12.2 billion years.
At the right part of the image we can see a small part of the Rho Ophiuchi cloud complex, at about 400 light-years from the Earth, which contains dark nebulae where lanes of obscuring dust hide background stars, blue reflection nebulae where the dust is illuminated by nearby stars and red emission nebulae where the hot hydrogen gas itself is glowing (the emission nebulae are not framed in this image).
Rho Ophiuchi is the double-star surrounded by IC 4604, the large blue reflection nebula at the right of the photo.