Some helpful advice from SkyNews Magazine for those who are thinking about trying astrophotography...
The Digital Revolution
In less than a decade, the swift evolution of digital cameras has created a new and powerful tool for amateur astronomers—the digital SLR (single lens reflex) camera. Now, for the first time, backyard astronomers have access to an easy-to-use technological marvel capable of a remarkable range of astronomical imaging.
The digital SLR cameras that have achieved the most impressive results in our tests over the past two years are the Canon 50D, 40D and XTi. While CCD cameras are still the method of choice for the top astrophotographers, results over the past year few years—in our opinion, almost as good—are being achieved with these latest digital cameras, and all at a fraction of the cost of the top-of-the-line dedicated CCD astrocameras. Modifed DSLR cameras — those with a filter added by specialized companies — can achieve even more spectacular results as compared to regular DSLR cameras.
Have you ever tried to take an astrophoto? Is it too difficult and expensive? The easiest way to begin is by simply placing a camera on a tripod and taking exposures of 10 to 25 seconds. Conjunctions, constellations and aurora images all can be taken with this method. For auroras or constellations, use ISO 800 or faster. With a wide-angle lens, set the camera to its lowest f-stop, focus at infinity, and take an exposure of 20 to 30 seconds. For sunset or sunrise conjunctions, try ISO 100 or 200 and exposures of 2 to 10 seconds. A cable release is a handy accessory, but most digital cameras have timer settings that allow exposures of different durations. While the SLR cameras above are preferred, some point-and-shoot models, mainly those with 5 megapixels or more, can achieve satisfactory results for brighter auroras and conjunction images at sunrise or sunset.
The key element to taking a good on-tripod image isn't necessarily the target, whether it be an aurora or a conjunction, but the composition of the image. Add an object to the foreground, such as a tree, person or a house. Each person's on-tripod image will always be different from someone else's no matter what the subject matter—a factor that allows each image to be unique to the author.
My first photo through a telescope...
Shooting through a telescope opens the door to a whole new and exciting world. Beginners are advised to start by taking photos of the Moon. Two methods can be used: Attach a camera directly to the telescope (turning the scope into a giant camera lens), or by place the camera up to the eyepiece.
Adapters are available that allow a camera to be attached directly to the telescope or to the eyepiece (contact your nearest vendor). Adapters can be purchased for a wide range of camera makes and models.
For shooting through the telescope, the image size of the Moon will depend on the focal length of the telescope. A focal length of 800-1200mm frames the Moon nicely. Exposure times will vary depending on Moon's phase and the focal ratio of the telescope used.
Recent improvements in technology have made planetary imaging much easier than in the past. Small cameras that attach directly to the telescope via a computer, such as the Celestron NexImage Solar System Imager, Meade's Deep Sky Imager or Phillips TouCam Pro webcam, can produce spectacular images. With the click of a computer mouse, a number of frames can quickly be taken. Afterwards, sort through the frames, discarding those that were adversely affected by poor seeing, and stack the remaining using either the software provided or free programs such as Registax. Stacking an image reduces pixel noise, resulting in a more detailed and sharper final image.
Those who excel at planetary observing often spend hours processing the images afterwards. Be prepared to spend some quality time with your computer!
Processing images with a computer
Adobe Photoshop is the most commonly used software for processing images. Some versions of Photoshop are included free with camera, printer or scanner software, and most will suffice for doing basic processing. Makers of digital cameras often include their own processing software as well.
While Photoshop does have a high learning curve, adjusting options such as levels, curves, colour balance, lightness/darkness and contrast are relatively simple to learn. Often some minor adjustments can bring out hidden details and improve an image dramatically.
Other popular imaging software includes programs such as Images Plus, K3CCD tools and Neat Image.
Click here to download the product review article "Cameras in head-to-head showdown" (SkyNews, March/April, May/June, 2007).
Sending images by e-mail or putting them on the Internet...
Once you have a spectacular image, you will want to share it with others. Many ISPs (Internet Service Providers) allow subscribers to create web pages. By creating your own web page, anyone can view your latest image with the click of a mouse. Some websites allow users to upload images and create their own on-line photo album free of charge. Often the size of the image will need to be changed for ease of viewing. This can be done using Photoshop or a similar program.
E-mailing is a popular way to share images. For best results, avoid reducing the physical size of an image (i.e., do not change an image to, for example, 400 x 600 pixels). Reducing the actual physical dimensions results in the loss of resolution. When saving an image, compressing the file to 7 or 8 still allows sufficient resolution but reduces the file to a size more appropriate for e-mailing.
Aurora image: Todd Carlson | Lunar image: Douglas Palmer | Saturn image: Darryl Archer