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Astrophotography DSLR Guide

Mr RobotJun 7, 2017, 9:25:09 PM

Astrophotography is the art of photographing the stars, astronomical objects and large areas of the night sky.

This can be achieved using a DSLR Camera and a lens, the lens can also be a telescope.  This guide will explore the requirements needed when using a lens and will explain how to set your settings in Manual Mode (M) on a DSLR.

What You Need (The Equipment):
A Camera:
A DSLR camera or camera with Manual Mode (M).
A lens: This seems obvious but you will need to be able to turn off auto focus.
A Remote Trigger/Timer: Simply pressing the shutter release will result in camera shake and this will distort the image causing blur.  If you don't have an external trigger the built in 10 second time will suffice.
A Tripod: Use a sturdy tripod to limit the amount of movement during shots.  Some tripods come with a hook underneath allowing you to hook your camera bag and create more stability.
A Head Torch: (Optional) You will be in the dark and it will help you in the environment.
A Torch: Preferably high powered, look for something with lots of Lumens (Lumens a measurement of the total amount of visible light (to the human eye) from a light source.)
A Smartphone:  (Optional) You are likely to be in a dark secluded place so theres the safety aspect to consider.  However, all smartphones come with GPS and you can use an app which allows you to point your phone at the sky and the constellations and stars will be shown.  I use Star Chart which is a free app on: Google Play Apple App Store

When & Where:The most important thing when planning your astrophotography adventure.  There is lots to consider as there are a few things that can throw a spanner in the works.  Light Pollution; this can be caused by a number of things.  Passing vehicles can cause unwanted light during a long exposure, so if possible look for somewhere away from busy roads.  Street lighting will be your worst enemy, depending where you are you might not be able to avoid that sodium orange glow on the horizon.  So try to get as far away from cities and towns as possible, it won't be the end of the world if you can't as you can tone it down during post process.  I use Dark Skies a website which lists the locations of the darkest places in the UK, there are other sites out there for other countries:http://www.darkskydiscovery.org.uk/dark-sky-discovery-sites/map.html

The Moon;  this will ruin your day.....well your night, a long exposure with moonlight present will make your shot look like it was taken during the day, so plan ahead.  I look online to find out when the next New Moon is and plan for that.  Failing that you could include the moon then tone down the glare in post or even use a gradient filter to darken the side the moon is on.  Here is a handy site that will help:

The Weather; I won't be going into detail here as this should be obvious, clear skies are best but a little cloud can add to your final image.Providing you can get at least the weather and the moon right you should be able to get at least something.  Be prepared to let down by these two factors but also be prepared to leave at a moments notice!

Image File Format:Shoot in RAW, a RAW file is the image data exactly as captured on the sensor.  This will make your life a whole lot easy when it comes to processing your photos as it will allow you to alter the image file in great detail.

The Glass (Lens):Ideally a wide lens with a low aperture (Something like f2.8 or lower.) to be effective.   Typically I use the Canon 10-24mm F2.8, a wider lens is better for capturing more of the night sky.  A low aperture will help a great deal as it will allow more light to hit your sensor, meaning more stars in your shot.

Exposure Timing (How long to shoot):This is important as the longer the exposure the more light and more of the universe you will see in your shot.  Longer doesn't necessarily mean better, the planet is constantly moving and this means that if your exposure time is too long you will pick up star trails.  This isn't a problem if you plan to have star trails in the final result, as shown below:

Source: https://en.wikipedia.org/wiki/Star_trail#/media/File:Star_trails_over_the_ESO_3.6-metre_telescope.jpg

You could just wing it, trying several exposures until you get it right but there is an easier way.The rule of 600, this is a process that determines the longest exposure for sharp stars (No star trails.), depending on lens and camera body i.e. full frame or crop sensor.   See this guide for info:http://www.capturingthenight.com/blog/wp-content/uploads/2012/09/web600rule.jpg

ISO (Digital Light Enhancement):ISO on your camera refers to film speed, this term was carried over from SLR film cameras and its function is to determine how sensitive the sensor is to light.  A high ISO is required to enhance light, in this case from the stars, typically 1600+, but experiment with this as high ISO = lots of noise.  Noise is the term used to describe grain on your final image, the higher the ISO the higher the amount of grain visible on your image.  This can be dialled down during post processing but can result in the final image looking washy or hazey.

Keeping Focused:This is one of the hardest things to get right!  Picture this; its pitch black and you can barely see you nose.  The camera can see even less, the likelyhood of getting your camera to auto focus is slim to none.  Here are a couple of tips to help:

1. Use the torch Luke.  This is where your high powered torch will come in handy.  Generally I choose a location with something in the foreground (A tree, rocks, a fence etc.), not only does this enchance your compostion but it will allow you (If close enough.) to shine your torch onto and use auto focus to catch a focal point.  Once you hit focus switch your lens to manual focus and you're good to go.
2. Live viewer.  This is the digital display (12 on image below.) that shows what the camera is seeing without using the view finder (Eye piece.).  Set up your prefered shot, set the lens to manual focus (MF) and then using the zoom option (Buttons 6 & 7).  Zoom in on one of the clearest stars (I use the North Star.) and turn your focus ring until you see the star getting focus.  Once your happy switch off Live Viewer, it is important to check that your settings haven't changed once switching it off as my Canon 7D has a habit of doing just that.  Also switching it off will preserve battery life:

Source: http://www.smashingcamera.com/dslr-body-buttons-explained/

Now this guide is a lot to take in and trust me it isn't the easiest technique to master, god knows I've tried!  I will include a couple of extra tips I have picked up which can produce better results.

Optional Tips:

Light Painting: If you have chosen to have a subject in your foreground you can use your torch to paint light on the subject, this involves shining your torch evenly over the subject during the exposure (The time the camera takes to complete its photo.).  This can bring out little details of the subject will can enhance your image greatly.  It may take a little practice to get right, my torch allows me to twist the head to focus the beam like a spot light.

Mirror Lock Up (MLU):It goes without saying that movement during long exposures is a no go area, "but I've got my sturdy tripod what more can I do?" I hear you say.  Most DSLR's will have the Mirror Lockup setting.  When enabled this involves flipping the mirror up out of the light-path just before the shutter opens, and then returning it when the shutter closes.  This reduces vibration and in turn reduces motion blur that can occur when the mirror hits the top of the mirror box.

Colour Temperature:You can customise your colour balance to match the colours in the sky, this isn't something I have used to often as results vary.  It can't help but to experiment on the night and see if it will benefit you.

I don't profess to be an expert on this subject so hopefully this guide will help you in your astrophotography adventure, these are tips that I have picked up along the way. 

Unforunatley living where I do the oppurtunities to hone these skills is limited due to the weather and personally I like to shoot the Milky Way, which isn't always visible enough to make it count.  Typically I will wait until its is mid way through the year as this is the best time to see most of the Milky Way.

Feel free to tag me in your posts to see how you are getting on.  I will be trying a different technique this year and I will be posting the results and maybe even a guide on how to do it, if it works great that is :)