Tech Talk – Star Trails

Who am I to talk technical about star trails…… be honest I have never even done one, but I have done a lot of research and I have attended some classes. I have done a fair share of night time astro photography, and I have done an astronomy class, so perhaps if I put all that together, I think I have a fair idea of what is going on.

“Well if you know how to do it, why haven’t you?” you ask……and that is a fair question. I will put it down to timing, a lack of certain equipment and lack of opportunity. Yes I probably should have attempted at Uluru (which is where I learnt about the Southern Pole, but no decent remote timer and lack of time to attempt such a feat).

Let’s start with the basics….

OK, so there are a few basic things you need to know if you want to make star trails; it needs to be dark, really dark, so no city lights and no moon are preferable. A really good star trail requires a lot of time and patience; minimum 2 hours shooting time, plus set up, if not even longer. A really great star trail usually has something interesting in the foreground; a building, a tree, an old car, a bridge – you get the idea. So you need to scout around and find a great location (one you can move around relatively safely at night), which is dark and has interesting objects. This can take time to source. Keep in mind the darker, clearer night skies are also usually in winter, so standing (or sitting) around in near freezing conditions is not necessarily fun.

What gear do you need….

  • First stop is a camera, a DSLR with manual shoot and bulb mode is a good place to start, the lens is better with a high f/stop (say f/2.8 or f/3.5) and approx 10 – 24mm, a zoom is OK, a wide angle is great, I have even used my kit lens for astro.
  • A remote timer trigger, I have recently just bought myself a new Pixel wireless remote for this sort of shooting, as well as normal astro, light painting and studio work.
  • Tripod – trust me when you have to take so many shots, in all the same place for 2 hours or more you need a good steady tripod
  • A comfy chair (you’re going to be there a while, so get comfy), warm clothes, blanket, Thermos of coffee, snacks etc.
  • Headlamp or torch, it will be dark, so either of these is good to see where you are putting your feet and to help setting up. A torch can also be good for ‘lighting up’ your fore ground object.
  • Lens cleaning kit, occasionally your lens can fog up if it is really cold, or dew collects on the lens, you may need to wipe between shots.

Let’s get technical….

The world is spinning in space and so are you, so when you are standing there taking a long exposure, the stars seem to move (it is actually you, but hey!). So any shot over 25-30 seconds and the stars will be blurry because they are moving, this is what we don’t wont for star trails. We want each shot to be of perfect clarity, its the end result in post that gives it the sense of movement, not blurry photos!

So set your shots to each about 20 seconds, you F/stop large (f/1.8 – f/3.5), focus approx Infinity or focus on the brightest star in the sky (easier said than done). Now crank up the ISO to approx 3200 or 6400, depending on your f/stop. Yes this may make your images grainy but it can be fixed in post. Try a few sample images to make sure you get something, anything.  Once you are happy with everything, switch the camera over to manual. Then you can start to set up your composition.

OK, so it is a clear, moonless night, you have the perfect location, how do you select where in the night sky to shoot? Now this is a recent piece of information I have just received and never knew it was really required before, perhaps I had never thought about it. For us in the Southern Hemisphere our stars revolve around the Southern Polar Light…….so if you want perfectly round, gorgeous star trails you need that as the central focus point of all images, or if you prefer just the corner, (See above images), and we have guiding lights to show us exactly WHERE it is. If you are in the Northern Hemisphere; you need to shoot towards the Northern Pole; Polaris (a.k.a. the North Star) is what you’re aiming for – it’s the last star on the handle of the Big Dipper, so if you can locate that you’re good to go. There are are great phone Apps that can help locate both Southern and Northern Poles as well; StarTracker for Android is one I use.

How do you find Southern Light?

Find the Southern Cross, just above and slightly to the left, are the two leading lights, one should be the brightest star in the sky. These are your cross points

Southern Cross-

So take the junction point between the two leading lights and the longer cross section of the Southern Cross…….this is the connection point, don’t worry if you can’t see any marker or star, they assure me it’s there. If you use that as the middle of your star trail, you can then move around to get the composition you desire.

You can take a Gray card shot and a white card shot to remove in camera noise later, this is personal choice, some say it’s a must, others say it’s not necessary. I guess if you do it the first time and make you own mind up later, it’s not that difficult. Personally I use my in-camera Noise Reduction for night shots, it can make a big difference. Then setting up your gear, on manual as per above and setting your remote to take a 20 second exposure every 30 seconds (2 per minute) for approximately 2 hours, so you will get roughly 240 shots; give or take. If you have to change batteries, wipe the lens, you may get less. Then sit back and relax, stay warm and let the camera do it’s work. Once it’s done you could re position for another angle, or call it quits and go home to a nice warm bed!You can shoot for longer, I have heard of people shooting for 6-8 hours! Now THAT is commitment! Or perhaps they should be committed?

Post Processing

This can be done in a variety of ways; using Photoshop or Image Stacker or Deep Sky Stacker (There are lots of others as well). I have heard that Image Stacker is very good. I won’t get into how to do your post processing, but there are two very good links below you may find useful and then there is always Google Search too!

Richard Gottardo – Photoshop

Lightstalking – Image Stacker and Deep Sky Stacker

Don’t forget the other option of creating a time lapse video in Photoshop……I mean you have all the images already right?

Images; Scott Ingram Photography & Robert Hensley

Til next time, happy snapping, peace and stay warm; I promise I will get some Star Trails before too long!