Aladin is a free, interactive sky atlas that draws data from a broad range of sources, giving you access to a very detailed all-sky view that’s comparable to the most advanced planetarium software. Aladin has advanced features like allowing you to query by object designation, coordinates, or even by image (I show you how to do that here in this tutorial).

I mention Aladin just once in my book and this is a tutorial on using it to explore the sky and use it to explore and investigate your own images.

I show you how to use Aladin to research objects and how to use it to research the objects in your own images by superimposing your images onto the Aladin Sky Atlas – a very useful feature that was once reserved only for those with expensive planetarium software.

Acquiring Aladin

It’s easy to get a copy of Aladin – just download it to your desktop and run it. You can download Aladin here: https://aladin.u-strasbg.fr/java/nph-aladin.pl?frame=downloading

You need to have Java installed on your system to use be able to run it. If you don’t have Java installed, you can get a free copy from https://www.java.com – just follow the directions there.

Running and Using Aladin

You run Aladin by double-clicking its icon on your desktop if you downloaded it onto your desktop.

When Aladin starts, it shows you a splash screen along with some options available on the left and right side of the window. A command bar at the top is where you do your searches for the objects you want to view.

Type M15 into the command bar and hit enter.

Aladin will acquire an image of Messier 15 and display it on your screen:

Find a star and click it to show some information about it (you may have to wait a couple of seconds after you click for Aladin to show the screenshot below):

In my case, I selected the star HD 204712. Use your mouse to click the name of the star and a new browser window should open at the Simbad entry for the star (I explained how to use Simbad here).

Use your mouse to click and drag the image to explore the area. You can also zoom in and out using your mouse wheel. You can investigate pretty much anything you see on the screen.

Try entering LEDA 9359 into the command bar and see what comes up. When you click on it, you’ll find that its designation is actually NGC 936. You can try pretty much any other designation.

As you move your mouse over the display, the command bar displays the celestial coordinates of your pointer.

Measuring Distances

With NGC 936 on the screen, click the third icon from the right side of the screen, as shown:

Click and drag across the galaxy to measure its size in arc minutes:

When you do something like measure or draw on the image, Aladin creates a new layer for you, as shown in the bottom right of the screen:

You can delete the layer by selecting it and then press the delete key on your keyboard.

Investigating Your Own Images

You can investigate what’s on your own images by superimposing them in Aladin, and then have Simbad highlight all of the known objects in your image. This can be useful for identifying things in your image or figuring out if you think you might have found something new. This feature used to be reserved for expensive planetarium software which was limited by the catalogs available to it. Using Aladin, you’re able to investigate millions of possible objects in your own images.

To use this feature, you have to plate solve your image (I discuss plate solving in the tutorial here).

Once you have your plate solved image, make sure there are no spaces in the filename, and then just drag the image from your File Explorer onto the Aladin window. In this example, Aladin is showing an image that I took and plate solved of NGC 5128:

Position your image in the window such that you can see all of it, right-click anywhere in the image, and click Locked View. This locks the view in place to prevent it from moving as you investigate your image.

You may have to adjust your image so that you can see it because it might be too dark or bright to see the details. Click the button labeled Pixel at the bottom-right of the screen as shown, to bring up the pixel mapping window:

Move the arrow in the center of the graph left or right until you can see the details in your image.

You may have to click the fourth button from the left at the bottom-left of the screen to orient your image such that it is right-side up.

To superimpose what Simbad knows about your image, expand the Collections folder at the left side of the screen, and click the arrow next to Database, your display should look something like this:

When you click the entry labeled ‘Simbad Astronomical Database’, a new window should pop up. Just click the Load button to load the result into your image:

Your screen likely has markers for all of the objects identified in your image. You can click any of the markers and get more information about the object as you did earlier in this tutorial. You can also measure distances as I showed you earlier – this can be useful for measuring the tail of a comet or the distance between galaxies.

Exploring The Area Around Your Image

You can explore the sky beyond your image by viewing your image along with Aladin’s view of the sky.

You do this by deleting the Simbad layer (highlight it and then press the delete key on your keyboard).

Then, on the left side of your screen, select Image – Optical – DSS – DSS colored (click the arrow beside each option and then click DSS colored), and click Load in the window that pops-up.

Select the layer with your image on it, and move the opacity slider to about the middle of the range, as shown:

Now right-click your image and select Locked View to unlock the view.

You should now be able to pan around, zoom in and out, and explore the region outside of your image.

If you get lost, highlight the layer with your image on it to highlight it in your display, and double-click the layer to return the view to the region of your image.

Conclusion

You learned how to download and use Aladin in this tutorial. I also explained how to investigate your own images using Aladin – this feature can be very helpful when you’re trying to find something in your own images.

Check out some of my other posts about image processing! Or visit the blog for more interesting articles.

Learn more about astronomy with my free book – Introduction To The Cosmos!