How to Photograph Constellations
Astrophotograpers are often concerned with making small objects in the sky look big, but the constellations are often overlooked.
When I was starting to get into astrophotography, the first thing I photographed was the constellations. Mainly because I didn't have a telescope, but I wanted to start with the big stuff first.
Photographing the constellations can be done with any camera the allows you to manually set the exposure. The next thing you need is a wide angle lens. Most compact "point and shoot" cameras have a wide angle of around 28 - 35mm, while dSLR owners will have a choice of wide angle lenses to choose from. For larger constellations, such as Orion, you will need something close to a 28mm lens, this will frame it with a border, while smaller constellations something closer to a 50mm lens is better. You should also set the lens aperture to its widest (smallest f/ number), but depending on the lens you may need to reduce it a stop or two if there are some distortions.
The next thing to consider is shutter speed. Unlike deep space imaging, constellations do not require long shutter speeds and tracking is not always necessary. To find out if you require tacking, I have a star trail calculator which will allow you to input the constellation coordinates, focal length and it will tell you how long an exposure you can use before starts will start to trail. In general, the further from the celestial pole, the shorter the exposure time.
ISO speed can vary depending on your lens and shutter speed, but aim for around 200 - 400 as a starting point.
Framing your image can be tricky, since you will unlikely be able to see anything through the viewfinder or live view screen. The solution is simple though... jump up the ISO as high as it will go and take a sample shot. You can adjust the framing as required and take another shot until you get the framing right. Raising the ISO level allows you to capture a brighter image with a shorter exposure, allowing you to frame the image quicker. Don't forget to lower the ISO again afterwards.
Light pollution could be a problem for you if you are in a light polluted area. Even if you are out in the countryside away from the lights, they may still be present on the horizon. This will create an orange gradient over your image. A light pollution filter will help with this, but you can also reduce this gradient using Photoshop and my light pollution removal tutorial.
The final thing you will need to consider is how to actually release the shutter. It may sound stupid, but the process of taking the picture is probably the most challenging. This is because when you release the shutter, you introduce a vibration to the camera. This vibration will make the stars wobble and adversely effect the image. The solution is to simply use a remote shutter release, or use the cameras built in timer. This will allow you to release the shutter without touching the camera.
While you are out, why not try stopping down the aperture a few more steps, to f/8 or f/11, decrease the ISO settings to around ISO 100 and take a long exposure and try and get some star trails! You will need bulb setting on the camera and a shutter release cable to take exposure longer than 30 seconds.
Last updated on: Wednesday 27th December 2017
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