By Alain Dussault
Deep sky or Celestial Objects. Definition of different objects
What can be seen with binoculars
To cover Deep sky objects, I refer you to the following astrophographies sites:
Diverse catalogues of deep sky object and other catalogues similar to
Celestial objects are classified in many categories, they are: open cluster, globular cluster, galaxies, nebulas, etc. the following site has articles on the subject:
On this site you would get a small description of each type of Deep sky objects with a photograph:
Open clusters are irregular group of stars plus or minus condensed, assembling a few dozens to hundred, or millions of stars. Those stars might be associated or be located in the same field of view. They are then composed of stars more disperse which received the name association, like Melotte 20, which is the Alpha of Perseus association.
Open clusters are generally the most easily objects to find with binoculars, because their principal components are brilliant stars. The most famous are The Pleiades (M 45), the Hyades (Melotte 25), the Beehive (M 44) and the double clusters of Perseus (NGC 869 and NGC 884).
There are many catalogues on open clusters for binoculars, the main ones are:
Collinder (Ex: Cr 399 - Coat Hanger) King Melotte (Ex: Mel 111) Stock Trumpler
These catalogues bear the name of those that have compiled them, and in general are objects for binoculars .
Globular clusters are immense swarm of stars in a spheroid form. They are compact formations of from 10,000 to million of stars concentrated in a sphere of 100 to 150 light-years diameter. They were formed when our galaxy was very young and are locate in galactic halo around our Milky Way galaxy, a vast region centered on the core of our galaxy. There objects are very far from us. Some can be seen with the naked eyes, and look like blobs in binoculars, like M13.
In a small telescope, we can resolve plus or minus some stars in globular cluster in using a high magnification.
The disk of our galaxy contains diffuse matter made of gas and dirt. At certain place we find concentrations of this matter, they are nebulas. Certain are obscure and absorb the light from the stars being, others shin like a neon sign. There are many types of nebulas.
Emission diffuse nebulas are clouds of gas excited by ultraviolet emission of very hot stars. These nebulas contains stars in formation and/or very young stars. The most beautiful object f this type is the Great Orion nebula (M42-43), visible to the naked eyes, in the winter sky.
Reflection diffuse nebulas contains interstellar dirt which diffuse or reflect the light form near stars. These stars are too cold to excite the gaseous component. The brilliant stars of the famous open cluster Pleiades (M45), appears enclosed in a luminous halo in photographs.
The planetary nebulas, are so named, because in small telescope, they appear spherical and of greenish color. They re composed of a gas extension around a star which has exploded in its evolution. Sometime the central star, which excite the nebula, is visible. As we see it through an envelop of gas, transparent and luminous, the perimeter seem more brilliant. that is why many planetary nebulas, have a ring form. the Ring nebula (M57) is a good example.
Finally certain diffuse nebulas are remnants form supernova explosion.
The Crab nebula (M1) is typical.
Galaxies, those vast agglomeration of stars in the universe, comprise dwarf elliptical galaxies, in dimension comparable to globular cluster, to giant spiral galaxies and even supergiant elliptical galaxies containing billions of stars.
The normal spiral galaxies are in the form of a flat disk, with a central globular core, surrounded by spiral arms. We designate this type of galaxy by the letter S, followed by the letters "a", "b" or "c", depending how their spiral arms are open. Galaxies of type SO are flat and bear no arms. Our galaxy and the Great Andromeda galaxy (M31), are of type Sb. This last galaxy is visible to the naked eyes.
The barred spiral galaxies looks like normal galaxies but have a luminous bar across their core, form which start the spiral arms. They designated by the letter SB followed by a "a", "b" or "c", according to their arms opening.
The elliptical galaxies might of spherical form, or elongated like a football. Their eccentricity is indicated by an rating from 0 to 7, after the letter E.
Irregular galaxies, identified by a I or Irr, contains many dust and gas and young stars. They do have have definite form. Magellan clouds, are of this type. These clouds are in the South hemisphere.
Particular galaxies are difficult to classify. They have a letter "p" with a particular qualitative.
Here is a list of deep sky objects, which are not Messier objects, but are visible in binoculars"
|NGC 129||00 29.9||+60 14||6.5||A.O.||21.0'||Cas|
|NGC 253||00 47.6||-25 17||8.0||Glx.||25.0'||Scl|
|NGC 457||01 19.1||+58 20||6.4||A.O.||13.0'||Cas||E.T. or Owl cluster|
|NGC 663||01 46.0||+61 15||7.1||A.O.||16.0'||Cas|
|Cr 463||01 48.4||+71 57||5.7||A.O.||36.0'||Cas|
|NGC 752||01 57.8||+37 41||5.7||A.O.||50.0'||And|
|Stock 2||02 15.0||+59 16||4.4||A.O.||60.0'||Cas|
|NGC 869||02 19.0||+57 09||5.3||A.O.||29.0'||Per||Double cluster|
|NGC 884||02 22.4||+57 07||6.1||A.O.||29.0'||Per||of Perseus|
|Mark 6||02 29.6||+60 39||7.1||A.O.||4.5'||Cas|
|Mel 15||02 32.7||+61 27||6.5||A.O.||21.0'||Cas|
|Tr 2||02 37.3||+55 59||5.9||A.O.||20.0'||Per|
|Tr 3||03 11.8||+63 15||7.0||A.O.||23.0'||Cas|
|Stock 23||03 16.0||+60 02||6.2||A.O.||15.0'||Cam|
|Mel 20||03 22.0||+49 00||1.2||A.O.||185'||Per||Alpha Perseus Association|
|NGC 1342||03 31.6||+37 20||6.7||A.O.||14.0'||Per|
|Kemble 1||03 58.0||+63 06||4.0||A.O.||180'||Cam||3 degrees chain of stars|
|NGC 1528||04 15.4||+51 14||6.4||A.O.||23.0'||Per|
|Mel 25||04 27.0||+16 00||0.5||A.O.||330'||Tau||The Hyades|
|NGC 1582||04 32.0||+43 51||7.0||A.O.||37.0'||Per|
|NGC 1647||04 46.0||+19 04||6.4||A.O.||45.0'||Tau|
|NGC 1662||04 48.5||+10 56||6.4||A.O.||20.0'||Ori|
|NGC 1746||05 03.6||+23 49||6.1||A.O.||42.0'||Tau|
|NGC 1807||05 10.7||+16 32||7.0||A.O.||17.0'||Tau|
|NGC 1817||05 12.1||+16 42||7.7||A.O.||15.0'||Tau|
|NGC 1893||05 22.7||+33 24||7.5||A.O.||11.0'||Aur|
|NGC 1907||05 28.0||+35 19||8.2||A.O.||6.0'||Aur|
|NGC 1981||05 35.2||-04 26||4.2||A.O.||25.0'||Ori|
|NGC 2169||06 08.4||+13 57||5.9||A.O.||6.0'||Ori|
|NGC 2232||06 26.6||-04 45||3.9||A.O.||29.0'||Mon|
|NGC 2244||06 32.4||+04 52||4.8||A.O.||23.0'||Mon|
|NGC 2251||06 34.7||+08 22||7.3||A.O.||10.0'||Mon|
|NGC 2264||06 41.1||+09 53||3.9||A.O.||20.0'||Mon|
|NGC 2281||06 49.3||+41 04||5.4||A.O.||14.0'||Aur|
|NGC 2301||06 51.8||+00 28||6.0||A.O.||12.0'||Mon|
|NGC 2343||07 08.3||-10 39||6.7||A.O.||6.0'||Mon|
|NGC 2360||07 17.8||-15 37||7.2||A.O.||12.0'||CMa|
|NGC 2403||07 36.9||+65 36||8.4||Glx.||18.0'||Cam|
|NGC 2527||08 02.5||-28 11||6.5||A.O.||22.0'||Pup|
|NGC 2539||08 10.7||-12 50||6.5||A.O.||21.0'||Pup|
|NGC 2571||08 18.9||-29 44||7.0||A.O.||13.0'||Pup|
|Mel 111||12 25.0||+26 00||1.8||A.O.||275'||Com||Com cluster of stars|
|IC 4665||17 46.3||+05 43||4.2||A.O.||70.0'||Oph|
|IC 4756||18 39.0||+05 27||4.6||A.O.||40.0'||Ser|
|NGC 6709||18 51.5||+10 21||6.7||A.O.||13.0'||Aql|
|NGC 6716||18 54.6||-19 53||7.5||A.O.||6.0'||Sgr|
|Cr 399||19 25.4||+20 11||3.6||A.O.||60.0'||Vul||Coat hanger|
|NGC 6819||19 41.3||+40 11||7.3||A.O.||5.0'||Cyg|
|NGC 6823||19 43.1||+23 18||7.1||A.O.||12.0'||Vul|
|NGC 6910||20 23.1||+40 47||7.4||A.O.||7.0'||Cyg|
|NGC 6934||20 34.2||+07 24||8.7||A.G.||5.9'||Del|
|NGC 6940||20 34.6||+28 18||6.3||A.O.||31.0'||Vul|
|NGC 7063||21 24.4||+36 30||7.0||A.O.||7.0'||Cyg|
|NGC 7160||21 53.7||+62 36||6.1||A.O.||7.0'||Cep|
|NGC 7209||22 05.2||+46 30||7.7||A.O.||25.0'||Lac|
|NGC 7235||22 12.6||+57 17||7.7||A.O.||4.0'||Cep|
|NGC 7243||22 15.3||+49 53||6.4||A.O.||21.0'||Lac|
|NGC 7789||23 57.0||+56 44||6.7||A.O.||15.0'||Cas|
Next chapter, The Color of Stars and Variable Stars
Preceding chapter, The Planets (Jupiter, Mars, Venus, Saturn and Mercury)
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Last update August 1st, 1999.