In this activity you will learn how to use Astrometrica to find the position of an asteroid, and then report those positions to the Spaceguard Centre.
To begin with, you will need to download a set of images from our website, and identify which object in them is the asteroid. This is the same procedure as in Level 1.
Once you have done this, you can identify the co-ordinates of the asteroid quite simply as follows:
- Whilst Blinking the images go to Tools >Stop Blinking
- Go to Image > Zoom In > 2x so that you can enlarge your view of the asteroid. If the asteroid is not near the middle of the image, you might need to use the window scroll bars to locate it. If you are not sure you are looking at the right object, you can always start blinking the images again to check that the object moves and is the asteroid.
- Position your mouse cursor (the cross) over the centre of the asteroid
- At the bottom of the screen you will notice that as you move your mouse cursor to the asteroid, there are a set of readings that change. Amongst these readings are the position of where you are pointing your mouse cursor. When you position the mouse over the asteroid, you are now seeing the position of the asteroid on the Equatorial Co-ordinate System. On the image below, the red area shows where the co-ordinates are displayed.
- Make a note of the co-ordinates and the file name which they are in (the filename is at the top of the window and starts with "Image X - Filename". X is the number of the image in your series.
- Go to Tools > Step Forward. This will show the next of your images.
- Repeart instructions 4, 5 and 6 above until you have the position of the asteroid in each of your images.
How Does This Work?
In the introduction we mentioned that astronomers use the position of the stars in an image to work out the position of the asteroid. In the files we have supplied to you, the position of the stars has already been worked out and the equatorial co-ordiate of the centre of each image has been embedded invisibly in the data in what is called a "header". The "header" contains lots of data about the image, and if you are interested in seeing this data you can load one or more of the images you have been using in Astrometrica and go to Images > Display Header. A new window will open, and you will be able to see all of the information contained in the FITS Header.
Submitting Your Measurements
The only thing left for you to do in this activity is submit your results to the Spaceguard Centre so that we can check them for you.
You will find a link to the Data Submission Form on the main Level 2 course page.
