Guide to Observing Deep-Sky Objects

Introduction3to the left side of the page. Included with each constellation rendering is a tableof the stars and their positions and magnitudes, as well as a table of Deep skyobjects, (all 110 Messier objects, 453 NGC, 1 Collinder cluster, 1 Melotte Cluster andthe Large Magellanic Cloud, for a total of 566) brighter than tenth magnitude, aswell as their sky positions and magnitudes.About the SoftwareThe CD-ROM accompanying this book has software written by the author.This software allows the user to determine what Deep Sky Objects (DSOs) areabove the horizon for a time determined by the user. This CD-ROM containsthe following files:1. deepsky.exe This is the executable program. deepsky.exe requires the followingthree files to work.2. DeepSkyObjectList.txt This is a text file that contains the database of the DSOsused by deepsky.exe.3. location.dat This is a text file that contains the user’s geographic location. Thisfile is described in detail below.4. deltaT.dat This is a text file that contains the difference between the Earth’sDynamical Time and Universal Time. This file is also described in detail below.When the program deepsky.exe is run, it produces a file named DSO.dat,which is a text file that tells the user what DSOs are above the horizon for thelocation described in location.dat at the time input to the program. This file tellsthe user the name of the DSO, what constellation it is in, what kind of DSO it is(galaxy, star cluster, nebula), its sky location (Right ascension and Declination, aswell as the Azimuth and Elevation), the visual magnitude, the angular diameterin arc-minutes, and a brief textual description of the DSO. Such a file allows auser to quickly and easily plan a night’s observing session, whether it be aftersunset, during the middle of the night, or before sunrise. The Azimuth in DSO.dat is to be regarded as a compass direction, measured in degrees. Azimuth =0 is North, 90 is East, 180 is South, 270 is West. Elevation is the angular distanceabove the horizon, also measured in degrees. Thus, Elevation will range between0 (right on the horizon) to 90 (being at the zenith point, directly overhead). Ifa DSO has an Azimuth of 105 degrees and an Elevation of 20 degrees, then thesky location of the DSO (at that given moment) is 20 degrees above the horizonspot that is 15 degrees South of East.Description of the FilesThe file location.dat contains the geographic information of the user’s viewing location.This file can contain the geolocation information for many different spots, butonly the first spot is used by the deepsky.exe program. If the user has several differentspots from which they may do some observing, then the data may be kept inthe file (recommendation: leave several blank lines between the blocks of data so as