Galaxy name

[CedrikG]

Hey folks !
Quick question :
A lot of galaxy start by the name NGC. while others begin with ARP and other ESO. In Exemple NGC 5866, ARP 87 (merging galaxy) and ESO 510 G 13 (My personal favorite galaxy )

Just wondering what mean these letter at the beginning.
Cheers !

[acey]

NGC is New General Catalogue, compiled by Dreyer and published in 1888. It was an expanded version of the earlier General Catalogue of John Herschel. All objects in the NGC were discovered visually, a large proportion of them by William and John Herschel. It covers the whole sky and includes virtually all DSOs known by 1888 (e.g. all the Messiers). So this is the bedrock of deep-sky viewing. If you want to refer to an object you use M number if it has one, otherwise NGC number. If it lacks an NGC number you need another designation - and you know that it will probably be hard to see.... There are some catalogues of star clusters that have easy targets (Melotte, Collinder...) and some recreational DSO lists that have acquired "catalogue" status (Caldwell), but in general, NGCs are the DSO junkie's bread and butter. There are about 7800 of them, all visible with a 12" scope at a sufficiently dark site. The early 20th century astonomer Bigourdan viewed all NGCs above his horizon in Paris (and measured their positions, and discovered hundreds of new ones). He used a 12 inch refractor.

Dreyer added two index catalogues, these have IC numbers. Many were visually discovered, but most were photographic. So you generally expect an IC object to be tougher than an NGC. The Horsehead Nebula, for instance, is an IC.

The Arp catalogue was compiled by Halton Arp, based on observatory photographs. It consists of "peculiar" galaxies. It has a very wide difficulty range but some Messiers and a lot of NGCs are also Arps.

ESO is European Southern Observatory. If a galaxy has ESO designation but not NGC then you can probably forget about using your eyeball on it.

There are lots of other catalogues. Once you run out of NGCs (7800-odd of them...) and ICs (over 5000) there's MCG, UGC, PGC, Hickson....

A few IC and UGC objects are unusually bright and can be seen in a 12" - I've seen a few. But the general rule is Messier first, then NGC, and beware of anything with a dramatic looking photograph but an obscure sounding designation. As for nicknames, the more we make up, the more confusing it gets. It's why catalogues were invented in the first place.

[CedrikG]

This is really an amazing and complete answer, thank so much for your time. Appreciate it, now I understand

[Earl]

I notice quiet a few fuzzy's in some of my images that don't plate solve as NGC's on astrometery.net are these potentially ESO's? or just not strong enough on the fit / jpg to register?

[acey]

In imaging it's easy to go well beyond NGC/IC. Which designation you use is a matter of choice.

There are UGC designations for about 13,000 northern hemisphere galaxies

MCG (Morphological Catalogue of Galaxies) has about 30,000 to a photographic magnitude of about 15

PGC (Principal Galaxy Catalogue) has over 70,000 galaxies.

One way to identify an object is by entering its position co-ordinates here:

http://vizier.u-strasbg.fr/viz-bin/VizieR

astrometry.net uses the USNO-B catalogue, based on scans from sky surveys over the last 50 years.

http://cdsarc.u-strasbg.fr/viz-bin/Cat?I/284