Data Sources I — Deep Sky Objects

Abstract

In Chapter 2 we looked at various software packages which displayed the night sky, its stars, planets and deep sky objects. These are in fact mathematical models which simulate the sky. In order to do this, these programs incorporate a variety of astronomical catalogues. Many of these catalogues are available via the Internet but first a word of warning. Every astronomical catalogue has errors. Even Messier’s catalogue of only 110 objects has one - the entry M102 is a duplicate of M101. John Flamsteed’s star catalogue recorded the planet Uranus (91 years before its discovery!) as the star 34 Tauri. The same is true for more modern catalogues, only more so because of their tens of thousands of entries. Even the Hubble Guide Star Catalogue, which you might assume to be perfect, has errors. These are due, in the main, to the automatic scanning process used which was confused by such things as plate defects, asteroid trails and unresolved stars. So when you discover something unusual, before you announce your discovery to the world, bear in mind the accuracy (or lack of it) in the data against which you are checking. Equally it is unfair to blame the software writer for these errors — they are doing their best with what is available.