Astrophotography a look at Digital Imaging
April 14th 2011 01:17
Category: CCD Cameras
Jupiter
In the past astrophotography was left to the professional astronomers for the most part they labored over photographic imaging plates developing film spending long hours to get one image.
With recent advances in CCD DLSR cameras and webcams astrophotography is available to almost everyone. In the last few years interest in amateur planetary astronomy has increased.
This is partly because imaging equipment has become reasonably inexpensive. Now amateur astronomers or those who have an interest in photography can capture images that would rival those taken by the professionals.
You can capture stunning images of the moon and some planets by simply using a webcam and a moderate telescope. The ordinary web cam can capture many sequential images using a short exposure time.
The exposures taken by a webcam use single frame images that can be stacked together forming one complete image. By comparison CCD cameras use longer exposure times and are usually cooled to almost freezing point the advantage is that using a CCD cooled camera has very few hot pixels and are less susceptible to noise. Hot pixels are noise artifacts that show up in a CCD image as little coloured dots.
Home brew webcam mounted on telescope
However the webcam is able to capture hundreds of images at a time. Although webcams have a much higher noise ratios, but the shorter exposures helps keep the noise down. This makes the images clearer because you can delete the fuzzy images and only use the clear ones to make up the final image.
It generally takes hundreds of webcam images stacked together to achieve an acceptable final image. Many of the frames recorded will not be worth keeping. I usually capture around 600 frames depending on the object to be imaged. Of the 600 frames I will use around 160 frames the rest are discarded.
image of Jupiter
This image ( above) of Jupiter is made up of 250 individual stacked frames using my home- brew webcam. The final image is almost complete it just needs more definition
The image below is
The final image of Jupiter digitally edited in Photoshop
Sorting and stacking hundreds of individual images manually would be about as much fun watching paint dry.
Now with computers and semi- automated programs editing and stacking images is a breeze. I use a program called Registax this make my job easier the program can sort and stack images together to make one complete image.
The rest of the editing is completed by using other programs like Photoshop of Gimp which allows you to tease out much of the detail within the image hopefully you will end up with an image you and perhaps the world can enjoy.
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