LEO
(April schedule, May schedule)

     Leo constellation is spring constellation and it is in best position for evening observing in April when it is high on the south sky. We will observe it in April when it is high on the south sky, and also we will observe it in May when it is high on the southwestern sky.

Double and multiple stars

     Alpha Leonis - Its name is Regulus. It is the brightest star in this constellation. Its visual magnitude is 1.3 and its distance from the Earth is about 78 light years. Regulus is main sequence star with mass about 4 times our Sun and with diameter about 3 times larger than our Sun diameter. Because it rotates very fast, its shape is not perfect ball but pretty oblate. So the poles are closer to the core, and they are hotter and thus brighter than the equatorial area of the star. Because of this its surface temperature is between 12,000 K and 13,000 K. If Regulus spins around its own axis a bit faster, it will disintegrate. Regulus is spectroscopic binary star, with the companion probably white dwarf. 
     Another companion have visual magnitude 7.7 and is separated about 180 arc seconds (or 3 arc minutes) on the sky from Regulus. Probably is physically connected with Regulus and they form true binary star system, but with period of hundreds of thousands of years. Its catalog number is HD 87884. Consists of small mass main sequence star and main sequence red dwarf with orbital period of about 600 years. The pair is about 800 billion km away from Regulus.
     Another companion have visual magnitude 13 and is separated about 210 arc seconds on the sky from Regulus. Probably is only visual companion in our line of sight.

     Gamma Leonis - Its name is Algieba. Its combined visual magnitude is 2.1. Its distance is about 150 light years from the Earth. Consists of two components with individual visual magnitudes 2.3 and 3.5. They are separated on the sky about 4.5 arc seconds.
     The component with visual magnitude 2.3 is a giant star with mass a bit larger than the mass of the Sun but already expanded and cooled and its diameter is about 25 times larger than our Sun diameter, and with surface temperature of about 4,500 K. 
     The companion with visual magnitude 3.5 is also giant star with larger mass than our Sun, already expanded and cooled with diameter 10 times that of our Sun and surface temperature of about 5,000 K. In reality it is about 30 billion km away from the first component and their orbital period is probably 1,000 years.

     54 Leonis - This double star is about 200 light years away from the Earth and has combined visual magnitude 4.3. It consists of two components with visual magnitudes 4.5 and 6.3. They are separated on the sky about 6 arc seconds. Both of them are main sequence stars, about twice more massive and with larger diameter than our Sun. They are hotter than our Sun with surface temperature about 9,000 K. The physical parameters of the stars are not 100% confirmed as correct, thus it is not known if this double is true binary star system or only visual double in our line of sight.

Deep sky objects
(will be observed only from dark location outside of the city)

     NGC 2903 - It is spiral galaxy. We see it tilted about 45 degrees on the sky. Its visual magnitude on the sky is 9.7 and it is about 30 million light years away from the Earth. 

     M 65 / M 66 / NGC 3628 - These are three galaxies very close apparently on the sky. They are called Leo Triplet, a small group of galaxies and they are popular target for observing by amateur astronomers. M 65 is spiral galaxy with visual magnitude 10.3 and it is about 35 million light years away from the Earth. M 66 is also spiral galaxy with visual magnitude 8.9 and it is about 36 million light years away from the Earth. NGC 3628 is spiral galaxy which we see edge-on on the sky. Its name is the Hamburger Galaxy. Its visual magnitude on the sky is 10.2 and it is about 35 million light years away from the Earth. It has prominent dust line along its plane, and on images the galaxy is divided on half with the mentioned dark line, and looks like hamburger.
     Leo Triplet Group of galaxies is also called M 66 Group of galaxies. M65 and M 66 are separated on the sky about 20 arc minutes, and 30 arc minutes equal distance from both galaxies on the sky is NGC 3628. In a telescope at low magnifications all three are visible in the same field of view.

     M 105 / NGC 3384 / NGC 3389 - Are three galaxies very close to each other apparently on the sky. M 105 is an elliptical galaxy. This type of galaxies do not have spiral arms. They have ellipsoidal shape and also are thicker than the spiral galaxies. We can understand the elliptical galaxy like a ball and we grab the ball from both ends and pull the ends away more or less. On the other side, the spiral galaxies are like thin flat disks. If we imagine a ball and slice it on thin pieces and take only the central slice, that will be the shape of the spiral galaxies. We can notice that spiral galaxies have structure - their core is called bulge and from the core extend several spiral structures called spiral arms. The bulge can be bigger or smaller and is thicker than the rest of the galaxy - it looks more or less like a ball.
     The visual magnitude of M 105 on the sky is 10.2 and it is about 30 million light years away from the Earth.
     NGC 3384 is elliptical galaxy apparently very close on the sky to M 105 and also in reality in space they are very close. Its visual magnitude on the sky is 10.9 and it is about 35 million light years away from the Earth. 
     NGC 3389 is spiral galaxy with visual magnitude 12.4 and also apparently very close on the sky to M 105, but in reality in space is about twice further from the Earth than M 105 is.
     All three galaxies can be viewed through a telescope at once, because all three can fit in the field of view of the eyepiece. NGC 3384 is about 7 arc minutes away from M 105 on the sky, and NGC 3389 is about 10 arc minutes away from M 105 on the sky.
     M 105 and its companion NGC 3384 are part of the M 96 Group of galaxies.

     M 96 / M 95 - Are both spiral galaxies with visual magnitudes on the sky 10.1 and 11.4 about 30 million light years away from the Earth. M 96 is about the size and mass of our galaxy, and we see it tilted on the sky. It is slightly deformed because of the gravitational interaction with the other galaxies around. M 95 is separated on the sky about 40 arc minutes from M96. Both galaxies can be seen through a telescope in the same field of view.
     M 96 is main member of the M 96 Group of galaxies which includes also M 95,  M 105 and its companion NGC 3384 and several more confirmed members and several more unconfirmed members. M 96 Group is also known as Leo I Group. It is part of our Local Supercluster of galaxies.