O tc Z o moving the focus ever so slightly, past focus one way, then the other, until I have bracketed the focus and I know it is as good as I can make it. It is a good idea to use vibration-damping pads under the telescope's tripod feet when a tripod is used. An electric focusing control can also be a handy tool, since that allows you to avoid touching the telescope. A breeze or wind can also play havoc with an imaging run.
At this point, the telescope is still working at //10. At //10 the image in the camera is big enough to capture the larger features on Jupiter's disk. But, we want even more detail. Now that Jupiter is in focus and centered in the field of view, I remove the camera and insert a 2x Barlow lens into the telescope in front of the camera so that the telescope is working at //20. Now I have a much larger image and even smaller features can be captured. I have often captured the small SSTB ovals with this configuration. Some amateurs take images at f/40 and capture some incredible detail. But remember, the focusing and other issues become more difficult as the image size increases. But it can be worth the effort, especially when the seeing is especially good. Once a sharp focus is achieved, the camera controls can be set. Clicking on "options" allows access to "properties". Click "properties" and the "video properties" screen needed to setup the camera for imaging appears. On the "image control" screen I normally set frame rate to "25", "brightness" to about 25%, "gamma" to about 45%, "saturation" to about 50%, and "auto exposure" to off. On the "camera controls" screen I set "white balance" to auto. Then I set the "shutter speed" between 1/25 and 1/50 s, depending upon the seeing condition, and I set "gain", from low to high at 50-75%. The computer displays a live view of Jupiter on the screen. When these controls are properly set, you can easily make out Jupiter's belts and zones on the computer screen. If you make the image too bright, the image you capture will be washed out and you will not be able to process it properly. Likewise, the image cannot be too faint. These pointers will get you started, but you should experiment to see what settings work best with your telescope.
Now it is time to take the stream of images. After closing out the "video properties" screen, click on "file" and "set capture file" will appear. Clicking "set capture file" allows you to designate the file your image will be saved to. I like to incorporate the date into the file name. This can help you organize your data base of images later. Once the file has been designated you can go back and click on "capture". Then click "start capture". Then click "OK" and the camera will start recording and the frame counter will show the number of images being taken. The video avi files will quickly take up a lot of memory. You will want to capture an adequate number of frames so that you have enough to align and stack; however, after a point, additional frames do not gain you very much. I like to take at least 500 frames. You can stop the picture taking process at any time manually by clicking the stop button, or you can set a time limit. I like to set a limit of 30 s. This time limit usually results in about 500 frames. Now I have an avi file that is between 300 and 400 MB.
After performing several imaging runs, the images will need to be processed. Sometimes I do this at the telescope while I am waiting for Jupiter to rotate and present a new view. This way, I can also make sure my camera settings are working for the seeing conditions, etc. Or, the images can be processed at any later date, at my convenience. The processing software Registax is a wonderful program that is extremely easy to use. The raw images often capture more detail than the observer could draw accurately by hand but they do not reveal the detail that is hidden within them. The Registax processing software will work magic on these images!
Registax is an easy program to use. Many of the applications used in this software are the same as those used to align, stack, and process CCD images. The raw avi
file frames are run through these applications to produce the final detailed image. It is possible to over process images. However, Registax allows you to monitor the progress of the processing and steps can be repeated and changed prior to saving the final image. With practice, you can become skilled with the application of this software in a short amount of time.
Once Registax is up and running, you will go to the file folder, as with any file, and locate your raw image file. Clicking on "select input" allows you to go to your file folder to select the raw image to be processed. Click on the image file you want to process. Then click "open". Now the raw image appears on the screen. Once Registax has the image loaded the processing can begin. You can process all the frames in the avi file or you can select a range of images by checking the "Show frame list". Once the list appears, designate the frames you want to include in the processing. Remember, we need enough frames to get a good, dense image with enough contrast and resolution. Normally I set the processing area to 512 pixels. Set the "alignment box pixels" to a number large enough to allow the alignment box to completely surround Jupiter's disk on the screen. Normally I set the alignment box pixels to 256. A white cross will appear on the screen. Move this cross to a feature on Jupiter you can make out, such as a bright spot or a festoon; then click the left button on the mouse. This will cause the "Aligning" screen to appear. Now you have successfully designated an alignment reference point on Jupiter's disk and you are ready to set up the alignment parameters. An FFT spectrum box will appear along with a "registration properties" box will appear along with the image screen. Also, various values will appear on the "aligning" screen that you will need to set. Under "Optimizing options" I normally set "Optimize until" to 1%, "Search area" to 2 pixels, and "Lower quality" to 80%. Under "Tracking options" I check "Track object". Under the other "Options" I check the "Alignment filter" and set it to 5 pixels. I set "Quality filter band" to start 2 and width 5. I check "use contrast", and I set "resample" to 2.0 and "Bell". I check "Auto-Optimization" and "Fast optimize". The other settings I leave blank. Now you are ready to align your images. Click the "align" button. Once the frames are aligned the program will "optimize" them. The "registration properties" box display will show the process of this step and indicate the frame order with best quality first and indicate graphically how close the alignment actually is. It takes my laptop about 12 min to align and optimize 550 frames with the settings I use. This aligning process does what is says; it takes all of the frames you have selected and, regardless of where they appeared in the camera's field of view, the software "picks them up and moves them so they are in the same position on each frame", using features seen on the planet itself to make the alignment. At least, that is how I visualize the process. After the aligning process is completed, the stacking process can be started.
To start the stacking process, just click on the tab labeled "Stacking" at the top of the computer screen. The stacking page will appear, displaying Jupiter's image along with a "Stackgraph". The stacking process does just what it says, it stacks or digitally adds all the images together. I think you begin to see the benefit of the procedures the Registax software is performing. Aligning and stacking multiple images will average out imperfections in the individual images. Plus, the weak color and contrast in single images is improved by adding several images together.
The "Stackgraph" is used to select the frames that will be stacked together. This graph represents the frames in order of quality, indicating high to low with a horizontal red line running across the top of the graph. This graph line tells you where the quality of the individual frames falls off. Eliminating the lower quality
Was this article helpful?