Make a tricolor image of NGC 1087 using infrared, red, and green images.
First, align the three images. Do this by finding the location of a star
near NGC 1087, and using it as a landmark to shift the three pictures.
To find your landmark star, first open the green image. Look for a star near
NGC 1087 that you can clearly identify in all three images. Use your mouse to
draw a small box around the star. Right-click
inside the box and select "PSF." Record the x and y coordinate of the star
(these are coordinates in the image, not in the sky). Do the same for the
red and infrared images.
Next, figure out how to shift the red and infrared images to match the green.
Find the difference between the x coordinates in the red and green image
(xr - xg). You need to know the direction of the shift,
so don't forget the sign! Do the same for the y coordinate (yr - yg),
and then for the x and y coordinates of the infrared image.
Re-open the r image. Click on the Geometry menu and select Shift. Enter the difference
between the r and g images, but reverse the sign (so you can shift the r image to
align with the g image). Save the image under a new file name. Do the same for the
Next, click on View and select (L)RGB. Type the name of the
infrared file in the red box, the name of the red file in the green
box, and the name of the green file in the blue box. Do not
include the .fts extension. Click OK. Adjust the max and
min brightness values until you see the image clearly.
What do you see?