Using SAO DS9 to Discover New Asteroids


The procedure described here is a logical continuation of Finding Known Asteroids and it assumes that you have performed all the steps in that procedure before you begin this procedure. So, if you have not performed all the preceding steps, go back and complete them before trying this procedure.

Step 1. Blink the image set looking for new asteroid.

Procedure Sub-steps Expected Result
At this point, you should be working in DS9, have four images loaded and aligned, have positions of known asteroids marked with a green region marker, and have the stretch set so that you can see the faintest of objects.

You should mark new asteroids with a region of a different color. To change the circle color for DS9, from the "Region" drop-down menu, mouse-over "Color" and select "Red".
Any circle you now create will be red. Try creating a new region and see if it is a red circle. If you click the circle again, it will grow handles. Depress the "Delete" key and it will go away.
Select a subsection of the entire image by using the "Zoom" drop-down menu. This menu is fairly intuitive so I will leave it to you to figure out. Zoom until you get an area about 512 (or more) pixels in width and height. (My monitor will not make 512 pixels in height at a magnification I like so I use about 350 pixels height.) You can drag the edge of the DS9 window to make the image wider or taller. Your goal is to use most of your screen to observe this sub-region of the image. Then "grab" the little green "window" in the "panner" panel at the top of the window. You grab it by putting the pointer in the green rectangle, depress and hold the left mouse button, and move the pointer to another position in the panner window. Then release the button. The goal here is to focus on a smaller section of the frame so that you can study it more carefully. You will eventually cover the entire frame so select and move the green rectangle in an order that you can remember. The main window will show a portion of the images that corresponds to the green rectangle in the panner window.
Select "Frame" -> "Match" -> "frame" -> "WCS". All the frames in the set will now be at the same zoom and centered on the same location.
Depress the "Blink" button and carefully search the blinking image for asteroids. If you find a new one, stop the blinking as before and mark the asteroid with a red circular region. I could give you advice for this operation but the best thing to do is to try it and then ask specific questions. Asteroids will move in very straight lines and will look very much like stars. Defects will move with a slight wobble and are often asymmetric. Very faint asteroids will not necessarily look like stars and may, in some instances, completely disappear.

If you are unsure, seek advice.
Repeat the preceding three steps, each time moveing to a different subsection of the images, until you have blinked the entire image. Repeating these operations might take a long time. If you work on 512 by 512 pixel subsections, there will be 16 subsections. Have another cup of coffee and get back to work.