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a mailing list for "deep sky" observers of all levels

What are "Deep-Sky Objects" anyway?

For those interested in learning more quickly, here are some sites with excellent explanations of the soul and the substance of amateur deep-sky observing:

Every passion has its object, and the object of amateur astronomy is the visible Universe! But the Universe is a vast and complex place, so that even amateur astronomers have to classify the various things they see "Out There" based on observable characteristics: After all, there are MANY different types of objects visible in our night (and daytime) skies. And each type of object may require its own distinct tools and skills to be well observed by us lucky amateurs.

Perhaps the most natural dividing line in all of astronomy is that between objects which are gravitationally bound to Earth's Sun on the one hand (the so-called "Solar System objects"), and everything which isn't on the other. We know many objects to be our fellow-travellers in orbit around the Sun: these include eight known planets (excluding Earth), all of their moons (including our own Luna), dizzying numbers and types of asteroids, long- and short-period comets, "meteoroids" (the specks of dust that cause shooting stars), "zodiacal dust" - and of course the Sun and Earth themselves!

Beyond the gravitational grasp of Sol however, lies a vast well of emptiness, reaching all the way to the nearest stars, and then far, far beyond. Inhabiting this daunting vastness are a whole unearthly menagerie of different objects - essentially all of which can be seen with your own eyes, if you have a little knowledge and skill!

This menagerie of visible objects in the depths of space are what amateur astronomers call "the Deep Sky". Of course, Deep Sky objects fall into categories as well! For amateurs, these categories tend to tell us something about how to observe individual objects, and (perhaps more importantly for our passion) what the real NATURE of these tiny, faint objects is...

Here are some of the basic types of objects which we amateurs love to observe in the Deep Sky, along with links to more info about each!
Open Clusters Globular Clusters Multiple Stars Variable Stars
Planetary Nebulae Bright Nebulae Dark Nebulae Supernova Remnants
External Galaxies Galaxy Clusters Galaxy Groups Quasars and Lenses

To find out more about the Deep-Sky take advantage of some of the wonderful resources available on the Web, including:
Deep-Sky Astronomy Resource Guide
History of the Discovery of Deepsky Objects
The Webb Society (worldwide deep-sky observing organization)
National Deep Sky Observers Society (NDSOS - U.S.)
Andreas Domenico's wonderful "Visual Deep Sky Observing": many sketches!
Palomar Digitized Sky Survey
NASA Extragalactic Database (Find galaxies by position with NED!)
SIMBAD - Professional Database for ALL types of Deep-Sky Object
Auke Slotegraaf's Deepsky Observer's Companion (DOC)
Messier45.com (see Deep Sky List Generator)
Paul Markov's interesting "Deep Sky Observing Articles"
Vast Array of Open Cluster Maps & Resources
Rainer Manoff's Astroecke (Astro-Corner)
Michael Geldorp's Deep-Sky Sketches
DMOZ Observing Projects - discussions of deep-sky sketches and observing
The NGC/IC Project (NGC & IC are catalogs of deep-sky objects)
The Double Star Library (a LARGE resource)
VizieR Astronomical Catalog Service
Variable Star Classifications (How to decipher those codes...)
American Association of Variable Star Observers
Free Astronomical Software...
Adventures in Deep Space: Challenging[!] Observing Projects
Abell Planetary Nebula Observations by Eric Honeycutt
Extensive Catalog of Amateur CCD Galaxy Images
Damian Peach's excellent article on Astronomical Seeing
(plus a link for estimating seeing at the eyepiece!)
Professional Links in Galactic Astronomy

AND REMEMBER: If you have further questions or comments about deep-sky objects or deep-sky astronomical observing, don't hesitate to share them with the subscribers of IAAC! Separate from the main IAAC OBSERVING LIST, there is also a special mailing list for DISCUSSIONS and ANNOUNCEMENTS relating to IAAC and to deep-sky, called netastrocatalog-announce. You may subscribe to this '-announce' list to read others' comments, or submit your OWN comments to the list by sending email to the address:

Clear skies!
Lew Gramer <dedalus@alum.mit.edu>