Messier objects, named after the French astronomer Charles Messier, are a set of 110 astronomical objects that include galaxies, nebulae and star clusters but explicitly excludes comets. Messier was only interested in comets but his findings were obscured with all sorts of other celestial bodies. He thus classed all non-comet bodies as Messier Objects that are represented by the letter ‘M’ and a number. This helped other comet Observers to narrow their search by avoiding these objects listed in the Messier catalogue.
Target Objects
I will be observing a few of these objects in this aided observation. My chosen objects are shown in the table below. I have chosen these objects as they are all galaxies and can easily be used to compare with each other.
Messier Object Name/Type Apparent Magnitude
M81 Spiral Galaxy +6.00
M31 Andromeda Galaxy +3.44
M51
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In space we use Right-Ascension and Declination. Right-Ascension is the distance measured along the celestial equator from the equinox to the hour circle of the point in question. When combined with Declination, these astronomical coordinates specify the direction of a point on the celestial sphere.
We are also able to use Azimuth and Altitude. Azimuth represents the direction in which the object can be found. It varies between 0° and 360 degrees. Like bearings, 0 degrees would be north, 90° east, 180° south, and 270° west. When the Azimuth has been found, you need to look at how high above the horizon in other words the altitude of the object is. Altitude ranges from 0° to 90 degrees, and measures the angle between the horizon, observer, and the object. If the number is negative it means it is below the horizon and cannot be seen. These are called Terrestrial coordinates. The coordinates of each of my Messier objects are shown in the following