14. Register and Stack Images by Identifying a Planet’s Outline
Register the planet’s image by drawing outlines around the image disk. Run the command cregister r r_cregistered 30 1194. This commands registers or aligns all the 1194 images in the r image sequence and creates a new set r_cregistered, with the appropriate threshold value of 30 to determine the outline of the planet, as determined in Step 12 by running the circle command. It will take a while for the registration to finish. Try different threshold values if the planet fails to register properly.
Stack the planet’s image by running the command add_norm r_cregistered 1194. This command stacks and normalizes the 1194 images in the sequence r_cregistered.
Adjust the sliders to display the image better. Save this image as red.fit. You will need to perform the same steps for the green and blue channels.
To align and stack the green channel, run the following commands: type load g1 to display the first image in the g sequence, then use the mouse to drag a rectangle and select the planet. Identify the correct threshold value as described in Step 13 Identifying the Contours of a Planetary Image. Run the command cregister g g_cregistered 30 1160, then register by typing add_norm g_cregistered 1194. Save this file into the Working Folder by clicking FILE > SAVE and then saving it as green.fit.
To align and stack the blue channel, run the following commands: type load b1 to display the first image in the b sequence, then use the mouse to drag a rectangle and select the planet. Identify the correct threshold value as described in Step 13 Identifying the Contours of a Planetary Image. Run the command cregister b b_cregistered 75 1160, then register by typing add_norm b_cregistered 1194. Save this file into the Working Folder by clicking FILE > SAVE and then saving it as blue.fit.
Here’s how the command toolbar looks like. Take note of the repeating pattern in the command’s syntax, because each channel has to be processed separately. The only difference is the threshold value, which, as described in Step 13, has to be determined through trial-and-error.
At this point, you should have three separate files, one for each channel: red.fit, green.fit, and blue.fit. Combine the RGB images to form a color image as described in Step 10 Combining RGB Channels.
Adjust wavelets as described in Step 12 Wavelets Adjustment.
Remove sky gradient artifact as described in Step 11 Removing Sky Gradient Artifact
Save a copy of the image in BMP format, jupiter.bmp. Use other applications to further enhance the image.
This is a work-in-progress, please revisit this page as I add new topics soon. For questions and clarifications, please leave a comment.
Night Sky in Focus | Astronomy and Amateur Radio © Anthony Urbano | Manila, Philippines