Galaxy Groups and Clusters: Observing aids to complete this guide

Galaxy Groups and Clusters Observing Guide

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Observing Aids To Complete This Program

The deep sky imager may use an array of specialized tools such as cameras and image processing software for astrophotography or CCD observations.

A 12.5-14" aperture telescope should be adequate for visual completion of this program, but a larger telescope will make it easier and more enjoyable. A larger scope will usually bring out more detail and reveal fainter galaxies. For CCD imaging, at least an 8" scope is recommended.

Sky charts and software programs such as Sky Atlas 2000, Uranometria, The Millennium Star Atlas, or your own custom MegaStar charts will assist your search.

Sky transparency and good seeing conditions are essential. One helpful hint is to observe the dimmer objects when they are nearest the zenith. Less atmosphere to look through and less light pollution, translates to a fainter limiting magnitude

Useful Star Atlases

Norton’s Star Atlas 2000.0 shows individual galaxies, but does not identify clusters. Galaxies are identified with their Revised New General Catalogue (RNGC) numbers or Index Catalogue(IC) numbers. Over 600 deep sky objects are shown on the maps of Norton’s Star Atlas 2000.0, and stars are plotted to magnitude 6.5.

Norton’s 2000.0 Star Atlas and Reference Handbook. Ian Ridpath, ed. New York: Longman Scientific and Technical and John Wiley and Sons.Sky Atlas 2000.0 shows individual galaxies but does not specifically identify galaxy clusters. However, clustering of galaxies is often apparent on the charts. Stars to magnitude 8.5 are included in the latest edition.. Galaxies listed in the Becvar Atlas of the Heavens are included, with a number of selected additions from works such as Vehrenberg's Atlas of Deep-Sky Splendors and the three-volume Burnham's Celestial Handbook. Deep-sky objects are labeled by their NGC (New General Catalogue) or IC (Index Catalog) number.

Sky Atlas 2000.0. By Wil Tirion. Cambridge, MA: Sky Publishing Corporation.

Uranometria 2000.0 also shows individual galaxies with catalog designations. Clusters are not labeled as such (except for the CrB cluster, Abell 2065), although clustering is often apparent on the atlas charts where there are many galaxies in a small area. Stars are plotted to magnitude 9.0. Transparent overlays are included for determination of celestial coordinates on the maps.

Uranometria 2000.0 (two volumes). By Wil Tirion, Barry Rappaport and George Lovi. Willmann-Bell, Inc., Richmond, VA.

During the preparation of this observing guide a second edition of the Uranometria Volume 1 and 2 and the Deep Sky Field Guide, much expanded and including galaxy clusters is scheduled to be published. All Uranometria page numbers refer to the 1st edition.

The Deep Sky Field Guide to Uranometria 2000.0 is an invaluable companion volume. Pages are numbered to correspond to Uranometria pages. all non-stellar objects are listed with coordinates and other data including dimensions, brightness, surface brightness, classification, and other notes.

The Deep Sky Field Guide to Uranometria 2000.0. By Cragin, Lucyk, and Rappaport. Willmann-Bell, Inc., Richmond, VA.

The Millennium Star Atlas has 10,000 non-stellar objects and is the only listed atlas that includes Abell galaxy clusters. The index also has a selected list of objects with special astronomical names (many of them galaxies and galaxy clusters). Stars are plotted to magnitude 11.0.

From "How to Use This Atlas," under Non-stellar Objects, Galaxy Clusters:

A pentagon symbol marks a rich cluster of galaxies that has at least 10 members of 16^th magnitude or brighter. In many cases, along with the pentagon, several of the brightest member galaxies are plotted individually. The prefix A refers to a number from the original northern and southern Abell catalogues: AS denotes a cluster in the southern supplement. The pentagon simply marks the cluster's location without indicating its angular extent. Most galaxy clusters in the atlas are smaller than 1/4 degree across.

The Millennium Star Atlas. By Roger W. Sinnott and Michael A. C. Perryman. Sky Publishing Corporation, Cambridge, MA.

MegaStar® is a computer software star atlas that has 110,000 deep sky objects and includes more than 15 million stars to approximately magnitude 15. MegaStar generates "eyepiece views" of objects and star fields, with deep sky objects plotted to scale and galaxies rotated to show position angle. In addition to the Hubble Guide Star Catalog, MegaStar includes the Tycho and Hipparcos catalog data. Virtual Telrad overlays and various filters and databases for selecting objects are included. MegaStar is compatible with the RealSky CD-ROM, overlaying sky survey images with atlas charts.

MegaStar Software. Willmann-Bell, Inc. Richmond, VA. http://www.willbell.com