Monoceros constellation is winter constellation and it is in best position for evening observing in February and March when it is on the southern sky.
In January it is climbing on the southeastern sky, in February and March is in best position for evening observing and is on the southern sky and in April is low on the southwestern sky.
We will observe it early in the evening in April when it is low on the southwestern sky before it sets behind the horizon.
Double and multiple stars
Epsilon Monocerotis - It is true binary star system. Other designation for this star is 8 Monocerotis. The visual magnitudes of the components are 4.5 and 6.5. Epsilon Monocerotis A is 122 light years away from the Earth and epsilon Monocerotis B is 121 light years away from the Earth. A is subgiant star and B is main sequence star. They are separated about 13 arc seconds on the sky.
Beta Monocerotis - It is triple star system and one of the most beautiful stars on the sky to observe. Its visual magnitude is 3.7 when we see it on the sky as a single star with naked eyes. Its distance is about 700 light years from Earth. The visual magnitudes of the components are 4.7, 5.2 and 6.1 and they are the same color. Component A has 7 solar masses, component B has 6 solar masses and component C has 6 solar masses. They are hot main sequence stars and given their large mass in the period of some million years the will stop fusing hydrogen in their cores, start expanding and leave the main sequence and become red giants. The separations between the components on the sky are 3 and 7 arc seconds, or in reality the distances between them are 90 billion km and 240 billion km. Their orbital periods are in thousands of years.
Deep sky objects
(can be observed only from dark location outside of the city)
NGC 2246 - It is a diffuse nebula. Its name is Rosette Nebula. Its visual magnitude on the sky is 9.0. It is about 5,000 light years away from the Earth. It is HII region where currently the stars form inside the nebula. Inside the nebula a lot of stars has already been formed, some of them are visible through the nebula. The open star cluster formed inside the nebula has catalog number NGC 2244 and its visual magnitude is 4.8. The diameter of the nebula is more than 100 light years. The massive bright stars in the heart of the nebula (and the cluster itself) with its strong ultraviolet radiation ionize the hydrogen which is main element in the nebula, and cause the nebula to emit light - usually that is characteristic red light when hydrogen ions recombine. That is why we can also say that this nebula is emission nebula. Usually this HII regions are more ionized inside than its outer zones which can be only partially ionized. The temperature of the inner parts of the nebula are higher than the outer parts of the nebula. Also some outer parts of the nebula are not at all ionized but the gas and dust reflect the light from the nearby stars, so we can also call this nebula reflection. As a conclusion we can call such nebulae where the star formation is going on emission-reflection nebulae, but they are more emission than reflection so usually we call them emission. Inside the nebula there are about 2,500 newly formed stars, some of them very massive hot O spectral class stars (O spectral class stars are those with surface temperature higher than 30,000 K).
NGC 2506 - It is an open cluster of stars. Its visual magnitude on the sky is 7.6 and lies about 11,000 light years away from the Earth. It is about 1 billion years old. In a telescope a it is a beautiful object to observe because a lot of stars can be seen. Its real diameter in the space is about 25 light years.
M 50 - Messier 50. It is an open cluster of stars. It is about 3,000 light years away from the Earth. Its visual magnitude on the sky is 5.9. Its diameter is about 20 light years and is about 100 million years old.
NGC 2264 - It is an open cluster of stars. Its name is Christmas Tree Cluster - because at low magnifications the main several stars of this cluster form an asterism which looks like tree. Its visual magnitude on the sky is 3.9 and it is about 2,500 light years away from the Earth. The star 15 Monocerotis (S Monocerotis is another name for the same star) is at the base of the tree. It is spectroscopic binary star system and both members are hot massive young O spectral class main sequence stars with masses 30 and 20 times bigger than the mass of our Sun. Their visual magnitudes are 4.7 and 5.9 with orbital period 75 years. They have companion about 3 arc seconds away with visual magnitude 7.8. It is also hot massive young main sequence star with mass equal to 5 Sun masses.
M 48 - It is an open cluster from Hydra constellation. Its visual magnitude on the sky is 5.5 and is about 1,500 light years away from the Earth. It is about 300 million years old.