Astronomy with an online telescope
Astronomy with an online telescope

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Astronomy with an online telescope

1.3 Messier objects in Stellarium

Stellarium can be set up to display the Messier objects so that you can see where they are in the sky. Also, for many of the objects you will be able to zoom in and see an image of the object.

To make sure that you have the correct settings enabled, select the third icon down in the left-hand menu (this looks like a star with a speech bubble containing different objects). This opens the Sky and Viewing Options window.

Described image
Figure 4 The sky and viewing options window in the desktop version of Stellarium. Mobile and tablet versions may vary.

Within this window select the DSO tab marked by a swirling galaxy icon (DSO stands for Deep Sky Objects). On this tab, make sure that ‘M’ for Messier objects is selected. You can also experiment with the two sliders marked Labels and in the Labels and Markers section to control the amount of information displayed on screen (you may need to be careful as displaying too much information can result in a screen that is very cluttered with symbols and names).

Close this window and return to the night sky view in Stellarium. You should now see all of the usual stars but also a variety of different symbols labelled with Messier numbers. As usual you can move around the sky and click on these objects to see more information about them.

You can also click on your chosen Messier object and press the forward slash key [‘/’] to zoom in and take a closer look at that highlighted object. What you see is a photograph (from a variety of sources) of that object taken through a telescope. When you're ready to go back to your original view of the sky, press the back slash key [‘\’].

[Note: on the mobile versions of Stellarium the display of Messier objects is enabled automatically, so you can simply use the search box to find an object and use the ‘+’ button to zoom in to see the image.]

Activity 2 Messier objects in Stellarium

Timing: Allow approximately 10 minutes

Having set the options as described, use the Search function in Stellarium to look for a variety of Messier objects.

  1. Search for the following objects:

    M31 – The Andromeda galaxy

    M42 – The great Orion nebula

    M66 – Spiral galaxy in Leo

    M11 – The Wild Duck cluster

  2. In each case, note what happens – in particular the height of each object above the horizon.

What do you notice about the display of each object?

Answer

You will probably have noticed that some of the objects are high in the sky, while others are low down or close to the horizon. In some cases the screen may appear to go blank. Don’t worry if this happens: take a moment to think about why this might be.

Why might an object not be visible in Stellarium?

Answer

On any given date and time, only some of the Messier objects are visible from Tenerife. The 110 objects in the catalogue are distributed across the whole sky, and some will be visible at different times of year to others, depending on where the Earth is in its orbit around the Sun. If Stellarium shows a blank screen, this is probably because the object you have searched for is below the horizon at the selected date and time and so is not visible. The four objects in this exercise were chosen because each is visible at a different time of year: M31 is best placed for viewing in the autumn, M42 in winter, M66 in the spring and M11 in summer.

In the next section you will learn how to use the RA and Dec coordinates of an object to work out whether it will be visible on any given date and determine what would be the best time of year to observe any particular object.

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