Milwaukee Astronomical Society

 

Beginner's Guide

Deep Space Objects

What is a deep sky object? It's any astronomical object that is outside our Solar System. This includes galaxies, nebulae, and star clusters.

 

Deep Space Objects Collage

Various Deep Space Objects. Warning: You will not see this visually!

 

Setting Expectations

You can see many amaxing deep space objects on the internet, and we have nearly a thousand of them right here on this website. For example, all of the images you see in the collage at the right were taken by members of the Milwaukee Astronomical Society. But unfortunately this is not what you will see visually with a telescope and especially a scope geared toward a beginner. It's not that the images were taken with instruments which are a lot larger than you'll have, but these are time exposure images. Most of these took hours of time to collect the photons necessary for such great images. With your eyes you only see the immediate photons of light arriving in your eyes.

But seeing objects with your own eyes is always more special than seeing a photograph. And we guarantee that when you do see photographs of what you've seen, you'll appreciate those images even more.

 

When, Where, and What Telescope?

Deep Space Objects (DSO's) are best viewed under dark skies. So the "when" is ideally a moonless sky. The "where" is a place where the skies are less light polluted. This is because in general these objects are relatively dim. So we have to talk about telescopes. After magnification the one big thing a telescope does is collect light. So the bigger the objective lens or mirror, the better. Then again, as telescopes get larger they also get heavier so not as easy to move and set up. This is why the Dobsonian telescope type is so popular with deep space observation.

 

Dark Adaptation / Averted Vision

When you're trying to view dim objects, it is imperative that your eyes become dark adapted. When moving to a bright location to a dark one, it is going to take some time for eyes to adjust. In bright light the pupils of your eyes contract so less light arrives to hit your retina. But getting dark adaptive is only half the battle. You also have to maintain it. That means using dim and especially red light for looking at your charts and accessories.

A technique that is very useful for observing dim objects is averted vision. It means not looking directly at your target, but looking away and seeing it in your peripheral vision. Your object will look amazingly brighter with this method. This exploits the anatomy of your eyes because you have two kinds of photo receptors: cones and rods. The cones are concentrated at the center. They are not particularly light sensitive, but they are color sensitive. The rods are outside of the cones and they are a lot more light sensitive. When the light is bright and your pupils are contracted, light does not hit them which is good because it would be painful if it did. The rods, however, do not discern color. If you've ever wondered why almost all the color goes away when it gets darker, it's because you're primarily using your rods. But bright objects like lights will show color because the cones are perceiving them.

Note that you should try looking around with averted vision. The rod density varies from person to person and you might find particularly good areas where there is a great density and thus you can see fainter.

A special note about the brightness of DSO's. When you read the magnitudes given for them that usually doesn't translate to really what you'll see in your telescope. The problem is they are generally giving you the total magnitude of the object. However, as you magnify the image that light gets spread out and effectively dims what you're seeing. So especially for finding DSO's, low power doesn't give you a larger field to find them, it also allows you to more easily see them. But after you've found them, the DSO might benefit from higher power.

 

Some "Easy" Deep Space Objects

"Easy" is a relative term. We've picked out these objects because they are easy to find or they are bright enough to be seen in most telescopes. Finding DSO's can be especially challenging when they're not very bright. It's not necessarily like a planet when you'll know immediately when it's in the field of view. A great method to find these objects is to use a method called "starhopping." We have a whole section devoted to describing the technique.

 

Orion Nebula
Orion Nebula in a small telescope - MAS image

Orion Nebula in a Telescope

Orion Nebula Finder Chart - Stellarium

Orion Nebula Location

The Orion Nebula is an Emission Nebula located in the constellation Orion. It is fairly easy to see naked-eye if you know where to look. It's located in the "sword" of Orion. The main nebulosity is M42. You might be able to see a wisp of nebulosity in the star to the upper left. That is M43. There is also a great grouping of 4 stars near the center of the nebula called the Trapezium. This grouping is easily resolved in even a small telescope.

See images of the Orion Nebula taken by members of the MAS.

 

The Pleiades
Pleiades in a small telescope - MAS Image

Pleiades in a Telescope

Pleiades Finder Chart - Stellarium

Pleiades Location

The Pleiades is almost a one-of-a-kind DSO in that it has the trifecta of visibility as it's a great naked-eye, binocular, and telescope object. It's easily spotted in the late fall and winter sky in the constellation Taurus. It is an Open Cluster and though there is a lot nebulosity associated with this grouping, it takes a fairly large telescope to detect it, but it's easily photographed so you'll see it in most of the images you'll find on the internet.

The Pleiades is also known as the Seven Sisters. But there are actually 9 stars recognized as the basic cluster because two of them are the parents. The Pleiades is also known to most amateur astronomers as M45.

See images of the Pleiades taken by members of the MAS.

 

The Andromeda Galaxy
Andromeda Galaxy - M31 in a small telescope - MAS image

Andromeda Galaxy in a Telescope

Andromeda Galaxy Finder Chart

Andromeda Galaxy Location

The Andromeda Galaxy is a fairly easy naked-eye object and yet it is 2.5 million light years away. But that makes it the closest galaxy and combined with the fact it is a large galaxy, it is largest apparent size galaxy. But it's actually 3 galaxies. The main big galaxy is M31 and it has two satellite galaxies, M32 and M110.

The Andromeda Galaxy is an easy object in binoculars, even in fairly light polluted skies.

Click here to see a starhopping guide to the Andromeda Galaxy.

See images of the Andromeda Galaxy (M31) taken by members of the MAS.

 

The Hercules Cluster
Hercules Cluster - M13 in a small telescope - MAS image

Hercules Cluster in a Telescope

Hercules Cluster - M13 Finder Chart

Hercules Cluster Location

The Hercules Cluster is better known as M13. It's a globular star cluster and the brightest one that can be seen in the northern hemisphere. It can be spotted in binoculars and telescopes less than 6 inches of aperture will show only a smudge of light.

M13 being a type of star cluster can benefit greatly by magnification. Stars benefit because it dims the background so therefore increases the contrast.

Click here to see a starhopping guide to the Hercules Cluster (M13).

See images of the Hercules Cluster (M13) taken by members of the MAS.

 

The Double Cluster
Double Cluster in a small telescope - MAS image

The Double Cluster in a Telescope

Double Cluster Finder Chart

Double Cluster Location

The Double Cluster is technically in the constellation Perseus, but to the eye it seems to be between Perseus and Cassiopeia. Oddly, this object does not have a Messier designation so it's generally called the Double Cluster. But the two clusters are fairly easy naked-eye objects so actually have star name designations: h Persei and χ Persei.

This is an okay binocular object, but it's really great in any sized telescope. And unless you use fairly high power, both clusters will be in the same FOV.

Click here to see a starhopping guide to the Double Cluster.

 

The Wild Duck Cluster
Wild Duck Cluster - M11 in a small telescope - MAS image

Wild Duck Cluster in a Telescope

Wild Duck Cluster - M11 Finder Chart

Wild Duck Cluster Location

The Wild Duck Cluster is better known as M11. It's a dense open star cluster in the constellation Scutum. It can be spotted in binoculars and telescopes and even small telescopes will show the individual stars.

M11 being a star cluster can benefit greatly by magnification. Stars benefit because it dims the background so therefore increases the contrast.

Click here to see a starhopping guide to the Wild Duck Cluster (M11).

See images of the Wild Duck Cluster (M11) taken by members of the MAS.

 

MAS Messier Observation List by Object Type

Here we list the entire Messier object list. It is called that because the author of the list was Charles Messier, a French astronomer. The original purpose of the list was to show the locations of fixed nebula and clusters so when a suspected comet was seen, it could be quickly verified.

Some important notes. The magnitudes for most of the objects is pretty good, but beware of those given for the nebulas which includes the galaxies. A great example is M33, the Triangulum Galaxy. It's shown magnitude of 5.7 would lead you to believe this is an easy object. But because it is a very large object by area, that brightness is spread out considerably. In most telescopes it's almost impossible to see, yet it's possible in dark skies to see it naked-eye.

Another important note about the star clusters including the globular clusters. These objects usually benefit from higher power. The reason is theese are stars and magnification doesn't diffuse a star image very much and improves the contrast as it darkens the background.

Open Clusters and Nebulas
No. NGC    R.A.   Dec. Mag. Type Con Size
M8 6523 18 3.1 -24 23 5 C/N Sgr 60' X 35'
M16 6611 18 18.8 -13 47 6.0 C/N Ser 7.0'
M17 6618 18 20.8 -16 11 6.0 C/N Sgr 11.0'
M20 6514 18 2.3 -23 2 6.3 C/N Sgr 28.0'
Double Stars
No. NGC    R.A.   Dec. Mag. Type Con Size
M40 WIN4 12 20.0 58 22 9 Dbl UMa 49"
Diffuse Nebulas
No. NGC    R.A.   Dec. Mag. Type Con Size
M42 1976 5 35.3 -5 23 5 DfN Ori 85' X 60'
M43 1982 5 35.5 -5 16 7 DfN Ori 20' X 15'
M78 2068 5 46.8 0 4 8 DfN Ori 8' X 6'
Galaxies
No. NGC    R.A.   Dec. Mag. Type Con Size
M31 224 0 42.8 41 16 3.40 Gal And 178'
M32 221 0 42.8 40 52 8.1 Gal And 8
M33 598 1 33.9 30 40 5.7 Gal Tri 73' X 45'
M49 4472 12 29.8 8 1 10 Gal Vir 9' X 7.5'
M51 5194 13 30.0 47 11 8 Gal CVn 11' X 7'
M58 4579 12 37.8 11 50 11 Gal Vir 5.5' X 4.5'
M59 4621 12 42.1 11 39 11.5 Gal Vir 5' X 3.5'
M60 4649 12 43.7 11 34 10.5 Gal Vir 7' X 6'
M61 4303 12 22.0 4 29 10.5 Gal Vir 6' X 5.5'
M63 5055 13 15.8 42 2 8.5 Gal CVn 10' X 6'
M64 4826 12 56.7 21 41 9 Gal Com 9.3' X 5.4'
M65 3623 11 18.9 13 6 10.5 Gal Leo 8' X 1.5'
M66 3627 11 20.2 13 0 10 Gal Leo 8' X 2.5'
M74 628 1 36.6 15 48 10.5 Gal Psc 10.2' X 9.5'
M77 1068 2 42.7 0 2 10.5 Gal Cet 7' X 6'
M81 3031 9 55.6 69 4 8.5 Gal UMa 21' X 10'
M82 3034 9 55.9 69 41 9.5 Gal UMa 9' X 4'
M83 5236 13 37.1 -29 52 8.5 Gal Hya 11' X 10'
M84 4374 12 25.1 12 54 11 Gal Vir 5.0'
M85 4382 12 25.5 18 12 10.5 Gal Com 7.1' X 5.2'
M86 4406 12 26.3 12 57 11 Gal Vir 7.5' X 5.5'
M87 4486 12 30.9 12 24 11 Gal Vir 7.0'
M88 4501 12 32.1 14 26 11 Gal Com 7' X 4'
M89 4552 12 35.7 12 34 11.5 Gal Vir 4.0'
M90 4569 12 36.9 13 10 11 Gal Vir 9.5' X 4.5'
M91 4548 12 35.5 14 30 11.5 Gal Com 5.4' X 4.4'
M94 4736 12 50.9 41 8 9.5 Gal CVn 7' X 3'
M95 3351 10 43.9 11 42 11 Gal Leo 4.4' X 3.3'
M96 3368 10 46.7 11 49 10.5 Gal Leo 6' X 4'
M98 4192 12 13.9 14 55 11 Gal Com 9.5' X 3.2'
M99 4254 12 18.9 14 26 10.5 Gal Com 5.4' X 4.8'
M100 4321 12 23.0 15 50 9.4 Gal Com 7'
M101 5457 14 3.3 54 22 8.5 Gal UMa 22.0'
M102 5866 15 6.5 55 45 10.5 Gal Dra 5.2' X 2.3'
M104 4594 12 39.9 -11 37 9.5 Gal Vir 9' X 4'
M105 3379 10 47.8 12 35 11 Gal Leo 2.0'
M106 4258 12 18.9 47 19 9.5 Gal CVn 19' X 8'
M108 3556 11 11.6 55 41 11 Gal UMa 8' X 1'
M109 3992 11 57.6 53 23 11 Gal UMa 7' X 4'
M110 205 0 40.4 41 41 9.0 Gal And 17'
Globular Clusters
No. NGC    R.A.   Dec. Mag. Type Con Size
M2 7089 21 33.5 0 49 7.5 GCl Aqr 12.9'
M3 5272 13 42.2 28 23 6.2 GCl CVn 16.2'
M4 6121 16 23.6 -26 32 7.5 GCl Sco 26.3'
M5 5904 15 18.6 2 5 6.65 GCl Ser 17.4'
M9 6333 17 19.2 -18 31 9 GCl Oph 9.3'
M10 6254 16 57.1 -4 6 7.5 GCl Oph 15.1'
M12 6218 16 47.2 -1 57 8 GCl Oph 14.5'
M13 6205 16 41.7 36 28 2.8 GCl Her 16.6'
M14 6402 17 37.6 -3 15 9.5 GCl Oph 11.7'
M15 7078 21 30.0 12 10 7.5 GCl Peg 12.3'
M19 6273 17 2.6 -26 16 8.5 GCl Oph 13.5'
M22 6656 18 36.4 -29 54 6.5 GCl Sgr 24.0'
M28 6626 18 24.5 -24 52 8.5 GCl Sgr 11.2'
M30 7099 21 40.4 -23 11 8.5 GCl Cap 11.0'
M53 5024 13 12.9 18 10 8.5 GCl Com 12.6'
M54 6715 18 55.1 -30 29 8.5 GCl Sgr 9.1'
M55 6809 19 40.0 -30 58 7 GCl Sgr 19.0'
M56 6779 19 16.6 30 11 9.5 GCl Lyr 7.1'
M62 6266 17 1.2 -30 7 8 GCl Oph 14.1'
M68 4590 12 39.5 -26 45 9 GCl Hya 12.0'
M69 6637 18 34.4 -32 21 9 GCl Sgr 7.1'
M70 6681 18 43.2 -32 18 9 GCl Sgr 7.8'
M71 6838 19 53.8 18 47 8.5 GCl Sge 7.2'
M72 6981 20 53.5 -12 32 10 GCl Aqr 5.9'
M75 6864 20 6.1 -21 55 9.5 GCl Sgr 6.0'
M79 1904 5 24.5 -24 33 8.5 GCl Lep 8.7'
M80 6093 16 17.0 -22 59 8.5 GCl Sco 8.9'
M92 6341 17 17.1 43 8 7.5 GCl Her 11.2'
M107 6171 16 32.5 -13 3 10 GCl Oph 10.0'
Open Clusters
No. NGC    R.A.   Dec. Mag. Type Con Size
M6 6405 17 40.1 -32 13 4.5 OCl Sco 15.0'
M7 6475 17 53.9 -34 49 3.5 OCl Sco 80.0'
M11 6705 18 51.1 -6 16 7 OCl Sct 14.0'
M18 6613 18 19.9 -17 8 8 OCl Sgr 9.0'
M21 6531 18 4.6 -22 30 6.5 OCl Sgr 13.0'
M23 6494 17 56.8 -19 1 6 OCl Sgr 27.0'
M24 6603* 18 18.4 -18 25 11.5 OCl Sgr 5.0'
M25 IC4725 18 28.8 -19 17 4.9 OCl Sgr 40.0'
M26 6694 18 45.2 -9 24 9.5 OCl Sct 15.0'
M29 6913 20 23.9 38 32 9 OCl Cyg 7.0'
M34 1039 2 42.0 42 47 6 OCl Per 35.0'
M35 2168 6 8.9 24 20 5.5 OCl Gem 28.0'
M36 1960 5 36.1 34 8 6.5 OCl Aur 12.0'
M37 2099 5 52.4 32 33 6 OCl Aur 24.0'
M38 1912 5 28.7 35 50 7 OCl Aur 21.0'
M39 7092 21 32.2 48 26 5.5 OCl Cyg 32.0'
M41 2287 6 47.0 -20 44 5 OCl CMa 38.0'
M44 2632 8 40.1 19 59 4 OCl Cnc 95.0'
M45 1432 3 47.0 24 7 1.6 OCl Tau 110.0'
M46 2437 7 41.8 -14 49 6.1 OCl Pup 27.0'
M47 2422 7 36.6 -14 30 4.5 OCl Pup 30.0'
M48 2548 8 13.8 -5 48 5.5 OCl Hya 54.0'
M50 2323 7 3.2 -8 20 7 OCl Mon 16.0'
M52 7654 23 24.2 61 35 8 OCl Cas 13.0'
M67 2682 8 50.4 11 49 7.5 OCl Cnc 30.0'
M73 6994 20 59.0 -12 38 9 OCl Aqr 2.8'
M93 2447 7 44.6 -23 52 6.5 OCl Pup 22.0'
M103 581 1 33.2 60 42 7 OCl Cas 6.0'
Planetary Nebulas
No. NGC    R.A.   Dec. Mag. Type Con Size
M1 1952 5 34.5 22 1 9 PlN Tau 6' X 4'
M27 6853 19 59.6 22 43 7.5 PlN Vul 8
M57 6720 18 53.6 33 2 9.5 PlN Lyr 85.6" X 61.6"
M76 650 1 42.4 51 34 12 PlN Per 163" X 107"
M97 3587 11 14.8 55 1 12 PlN UMa 202" X 196"