A necessary addition to any list of observing galaxies, the Andromeda Galaxy is our nearest galactic neighbor and one of the brightest Messier objects. Andromeda is a close analog to the Milky Way galaxy in many regards, and provides a fantastic visual opportunity to dive into closer observation of a galaxy, due to its size in the night sky.

An important note is that Andromeda is a bit of a late bloomer within galaxy season, and while it can be observed in the spring, it does not rise in the night sky until much later than other notable galaxies. Personally, I don't find it worthwhile to wait until three AM for a target over just categorizing it as a summer object, however either is technically doable.

Under very dark skies, it is possible to see Andromeda with the naked eye. In my opinion it is one of the most interesting naked-eye objects, simply due to the awe inspired by perceiving another galaxy right in front of you, without any other assistance. While some people purport it is even possible to observe without a telescope in areas with moderate light pollution, I've never done this, and it would certainly not be as easy a task.

Spiral galaxies! Oddly shaped galaxies! Oddly named galaxies! Gravitational interaction! A third, hidden galaxy! What more could you ask for?

Bode's Nebula (center), the Cigar Galaxy (top left), and NGC 3077 (very faint, middle/top right) are all in close enough proximity for gravitational interaction, which in this case strips hydrogen gas from all three that can be seen (by more powerful optics) filling the space between them. This gravitational interaction also allows gas to fall into the centers of M82 and NGC 3077, resulting in star forming and starburst activities at their centers.

While best observed in April, the galaxy's proximity to the North Celestial Pole means they are not too difficult to spot almost any time of the year.

A rather unique galaxy in the night sky, Whirlpool is a spiral galaxy that can be observed interacting with another smaller galaxy, NGC 5195. Due to its orientation, facing Earth face-on, and the detail this allows observers to resolve within the arms, the Whirlpool Galaxy is capable of highlighting star-forming regions, and the way they are affected by interaction with another galaxy.

The image on the right was taken with a DSLR and a very short lens; an observer with even a small telescope, or a Celestron 130GT, will be able to resolve great detail during its optimal viewing month of May.

Unique amongst the other galaxies highlighted here, Sombrero faces us almost perfectly from the side, showing just how flat some galaxies are. At the center of the Sombrero Galaxy is thought to be a massive black hole absorbing material from a smaller, inner disk at the galaxy's core.

The Sombrero Galaxy is best observed in May, where it rises high in the night sky very early, and can be resolved without difficulty with the Celestron 130GT telescopes. (NASA, Hubble, STScI/AURA, 2019)

While we can never actually see our own galaxy in the same way as we can many others, we can observe some of the densest bands of gas, dust, and stars from Earth.

This is something better suited for naked-eye viewing, as a telescope would be much too zoomed it. In dark skies and optimal timing (mid- to late summer) the Milky Way is very easy to see, and is an incredibly impressive sight to behold. In late fall or spring, when viewing is not as optimal, it is still relatively easy to find, however less bright and vibrant. Even under very sub-optimal conditions, such as in the winter and from a bright spot on campus it is possible to see the Milky Way, however it requires a bit more experience, and will only appear as a faint band. All of the people I've tried to show under these conditions have just called me crazy.

The original Messier catalogue, and several iterations of the New General Catalogue all the way through the 20th century include objects called spiral nebula, a source of heated debate in astronomy that peaked in the early 1900's. While the debate was solved one hundred years ago, and is now very well understood, we can observe the same relavent phenomenon with a modern small telescope and prove the same conclusion that is now a fundamental piece of astronomy knowledge. Note: to manually collect the data necessary to prove this using intergalactic stars, one would need a telescope slightly larger than the Celestron 130T's, however plenty of data is available publicly online for this. The same exercise can be done with variable star within the Milky Way, just not in the context of proving the Great Debate.

The argument derives from ambiguity about the size of the Milky Way galaxy, and a limitation of optical equipment from the time. One side argued that our galaxy, the Milky Way, was a large portion of the universe, and these spiral forms were nebula within our galaxy; the other side argued that these were unique galaxies outside of our own, and simply too far away for stars to resolve into point-light sources which instead blurred together.

This debate was resolve when Edwin Hubble used the 100 inch Hooker Telescope on Mt Wilson to identify variable stars within M31, using these to prove a distance even greater than the largest proposed extent of the Milky Way.

Due to the very direct relationship between period and luminosity of the Cepheid variety of variable stars that Hubble observed, the resolution to this argument is something we can also prove with some modern telescopes.

You can also refer to this image from some lecture notes by OSU Prof. B. Ryden which shows a Cepheid variable star in M110 (significantly farther than Andromeda) and can be used for the same calculations.

The following equation describes the exact relationship between period and absolute brightness:

Mv = - [2.76 (log10(P) - 1.0)] - 4.16