Wednesday, 26 February 2014

Basic night sky photography.

Ok folks so here I am going to attempt to pass on some of my knowledge about taking photographs of the night sky.
For those of us who are lucky enough to not live in a major city (exclude me) the night sky is an amazing sight when you look up. Those of us who do live in a city will see only a fraction of what is actually up there due to the light pollution.
With this in mind the first thing you are going to want to do when imaging the night sky is to get out of the city. It isn’t practical in England to have truly dark skies but you can give yourself a fighting chance.
In this section I am going to deal with simple straight forward night sky shooting and leave the stacking for another time.

Now you are hopefully away from the worst of the light pollution you can sit your camera on its tripod and pour yourself a nice hot chocolate. Give your eyes 5-10 minutes to adjust to the darkness and then if you look south and up if you’re lucky you will see the milky way in all its majesty.
 Really you can see it with the naked eye and it is amazing. Now to capture this in a photograph we are going to have to take a few things into consideration. In general terms you will want to set your camera to ISO 1600 with an exposure of 25 to 30 seconds. Depending on what lens you are using and how much star trailing you are willing to accept will be a factor in the exposure time. As a general rule of thumb you divide 600 by the focal length of the lens not forgetting any adjustment for sensor size.
An example would be my 17-85mm lens set at 17mm on a Canon EOS 7D So 17x1.6 for sensor crop thingy gives us 27.2ish, 600 divided by 27.2ish gives us 22ish. So to avoid trailing stars I would have to use an exposure of 22ish seconds. Im using ish a lot because all of the setting are very ishy to be honest but it gives you a starting point. You will then want to open up the lens to it’s widest aperture and the close it one stop.

Switch your lens to manual focus and focus it to the infinity mark, that’s the lazy #8, it looks like a number 8 laying down for those of you that don’t know.
Now you will want to minimise any movement of the camera on the tripod whilst the exposure is taking place so if it is windy remove the neck strap and if you don’t have a cable release use the timer setting to trip the shutter. If you really want to go belt and braces you could also use the mirror lock up.
After you have your shot make any adjustments you feel are needed to the settings and take another shot. Again make any adjustments to ISO exposure etc and take some more. To add a little more interest maybe include some of the surrounding landscape however be aware that the more your camera is towards the horizon the more light pollution will creep into shot. This can sometimes be quite effective but most of the time it’s a pain in the ass.
If your really lucky you may even get a meteorite etc fly across your shot whilst the shutter is open.
When you have your shots the next thing to do is to load them into your processing software. I use Lightroom and Photoshop and switch between them making adjustments. The luminance control in lightroom is very very good for controlling the noise in the image and bringing out some of the colour whilst I find Photoshop great for doing several curves and levels adjustments.
Right so there you go, a basic starter for ten introduction to taking photographs of the night sky. 
Cheers Gary

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