How to Image a Comet

How to Image a Comet

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The problem with comets and imaging is that comets are at their brightest when closest to the Sun. This means that comets are usually most visible at sunset. This is a difficult time of day to obtain good images as the daylight is constantly changing colour and brightness. A faint comet can easily be lost in an under or over exposed image.

The Required Tools

The best tool for the job is probably a DSLR camera, a tripod and a remote shutter release. Make sure the camera is fully charged and you have all the memory cards you need. This is especially important when imaging comets as you may need to travel to a site that offers a clear view of the low western horizon.

The Required Technique

The DSLR is a great option as you can use the screen on the back to make immediate adjustments to the ISO, aperture and shutter speed. The constantly changing conditions at sunset make the settings a bit of guesswork to start with. I would recommend starting with the aperture one or two stops down from fully open (low f number), have the ISO set to 100 or 200 and then calculate your longest exposure time using the rule of 600 (click the link to learn about the rule). The longest exposure time is dependent on the focal length of the lens you are using. For most standard kit 18-55mm lenses using the 55mm setting, the maximum exposure time to avoid trailing would be about 7 seconds (assuming a 1.5x crop factor sensor). If you find the image is too dark then start by increasing the ISO setting. If the image is too light then reduce the shutter speed. Take lots of pictures but make sure you continually check the images on the screen on the camera as the settings may need to change after every few minutes.

Have fun and please share any images you take.

Image credit: Philipp Salzgeber

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