Observing Galaxies
Follow the tips below to maximize your galaxy viewing experience.
1. Galaxy Basics
Galaxies are large collections of stars, gas, dust, and dark matter typically consisting of millions to billions of stars. They sit among the cosmos almost as island universes, separate collections of worlds sitting millions of light years apart. Galaxies are the farthest objects we can see with the Andromeda galaxy being the farthest object able to be seen by the naked eye.
Galaxies come in 3 main types spiral, elliptical, and irregular. Although we may try to keep galaxies in these nice and neat categories, reality is much more messy. Galaxies interact with one another, merge, and are torn apart and the results of these gravitational interactions can be seen in the galaxies we observe today.
Galaxies usually come in groups called galaxy clusters. The closest major galaxy cluster to the Earth is the Virgo cluster, which has tens of galaxies that can be seen with a medium-sized telescope from a dark sky.
Markarian’s Chain in the Virgo Cluster
2. Introduction to Observing Galaxies
Galaxies shine with the light of millions and millions of unresolved stars and as a result, emit light across a broad range of wavelengths. This broadband emission, unlike line emission from ionized gas in nebulae, encompasses the entire visible spectrum and beyond. As a result, there are no filters that can be used to substantially improve views of galaxies. A light pollution filter like a CLS may be of some benefit.
In dark skies, galaxies that are barely visible from cities can completely fill the eyepiece. The only effective filter for galaxies is gas to put in a car to drive to dark sites.
This has led to two strategies for observing galaxies low magnification and large exit pupils to maximize surface brightness, and high magnification and small exit pupils for the highest possible contrast.
The low magnification strategy is recommended for most observers. High magnification views will have higher contrast but will make everything appear extremely dim, requiring an experienced eye to see.
Simulated view of Andromeda in Binoculars
3. Choosing the Best
Simulated comparison view of an easier-to-see edge on galaxy vs. a face on galaxy
Galaxies are quite difficult to see in bright suburban skies and every method to increase the chance of seeing them must be taken.
Galaxies with bright cores or those that are edge-on are easiest to see.
Most galaxies have cores that are brighter than their outer extensions and only their cores will be visible. Galaxies with the brightest central regions are easiest to see.
Galaxies also appear at a variety of angles from face on where the entire disc is visible, all the way to edge on where the galaxy is reduced to a thin fuzzy glowing line marked with a dust lane down the middle. Edge-on galaxies appear brighter than face-on galaxies of the same magnitude as more of their light is concentrated into a smaller apparent area.
4. Notable Galaxies
Eyepiece recreation screen calibration aid
The following galaxies have been verified to be visible from bright suburban skies. Other than the Andromeda, all other galaxies may be difficult for a beginner to observe.
All galaxies below have an eyepiece recreation that best represents what they appear like from bright suburban skies. These recreations represent the view when the object is high in the sky, and an actual view may be dimmer when the object is low. The views are also made assuming the viewer has had at least 3 minutes to dark adapt. If the listed objects are viewed with no dark adaptation or while looking at lights, the object will appear much dimmer than recreated.
To make the eyepiece recreation as realistic as possible set the screen brightness to the highest setting and lower it until the 8 rectangle is barely visible. A dark sky will provide much better views in comparison to the eyepiece recreations and is always recommended.
Best and Brightest
From bright suburban skies I have only been able to see a few galaxies without the use of observatory-grade telescopes. This list will grow as I develop the techniques to see more of them.
The Andromeda Galaxy
Messier 31 / NGC 0224
Type: Spiral Galaxy
Magnitude: +3.4
Aperture: Naked eye or Binoculars
Observing Months: October - April
Size: 180 x 59 Arcminutes
Distance: 2.58 Mly
The Andromeda galaxy is the closest major galaxy to our Milky Way. Its size has been approximated to be a bit larger than our Milky Way galaxy and appears as a faint smudge several times larger than the full moon in a dark sky.
When visually observed the glow from the central bulge dominates the view and appears as an elliptical glow with a bright center. The core almost has a fractal nature and appears the same at both low and high magnifications. In sufficiently dark skies the shadows of the dust lanes can be seen.
Like most galaxies, Andromeda is not alone in space and has many satellite galaxies. The largest and most prominent of the two are M 32 and M 110. M 32 can be seen in the same field of view at low magnifications, and M 110 may also be simultaneously visible with sufficiently low magnifications. M 32 is easily visible from bright suburban skies and M 110 may or may not be visible depending on your local sky conditions.
Use very low magnifications and large exit pupils to fit as much of the galaxy as possible into the field of view. Binoculars and dark skies are needed to see the galaxy’s full extent stretching across the sky at over 5 full moons across.
Bode’s Galaxy
Messier 81 / NGC 3031
Type: Face on Barred Spiral Galaxy
Magnitude: +6.9
Aperture: 100mm+
Observing Months: January - July
Size: 25 x 11 Arcminutes
Distance: 12 Mly
Bode’s galaxy is perhaps the easiest galaxy to see from mid-northern latitudes outside of the local group. In a low power eyepiece both M 81 and M 82 can be seen sitting side by side. From bright suburban skies only the central bulge can be seen, and under very transparent conditions faint hints of the spiral arms may be visible.
Since no filters will help in observing this galaxy, wait for the object to be as high as possible. This usually happens around February or March in the late evening. Since this time of year also means some of the coldest temperatures of the year, the moisture coming off of your eyes may fog up the eyepiece. Any fogging of the lens will prevent M 81 from being visible against the background sky glow. Use a small dew heater strap to heat the eyepiece, or use a microfiber to wipe off the humidity.
Start at low magnifications to find the object and then increase to medium magnifications and exit pupils between 3-4 mm. The sky darkening from moderate magnification helps to improve contrast.
Cigar Galaxy
Messier 82 / NGC 3031
Type: Edge on Spiral Galaxy
Magnitude: +8.4
Aperture: 100mm+
Observing Months: January - July
Size: 11 x 4.3 Arcminutes
Distance: 12.3 Mly
The Cigar Galaxy, as its name suggests, appears as a silver cigar-shaped streak in the night sky. Sitting less than a degree away from its brighter companion, Bode’s Galaxy M 81, M 82 can cut through light pollution more effectively despite being dimmer.
Being edge on M 82 has a high surface brightness and does best at medium magnifications. In a dark sky at high magnifications, the dust lanes that shadow the glow of the galaxy can be seen crossing across its disc.
M 82 is a starburst galaxy and is currently undergoing star formation at a rate 100 times higher than our Milky Way. The deaths of constantly born and short-lived massive stars puff out the gas from the galactic disc as they undergo supernova explosions. The best analogy for this is to imagine a bag of popcorn filling up with air and expanding as the kernels pop. Visually with the use of a UHC filter, the effects of this vigorous star formation can be seen as fine streaks among the dust lanes.
Just like M 81, start at low magnifications to keep surface brightness high and increase as desired based on your telescope’s capabilities and local viewing conditions.