Startrail in Morocco
Ever wonder how those Star trail images were made?
Wonder no more, because I am going to show you step-by-step in this tutorial. Although for ease of use it is helpful to have a basic understanding of how a camera works or how to use post-processing software, it is not entirely necessary if you use my guidelines.
But there are some requirements regarding your equipment, as we'll need a camera that can capture a series of long exposure images over the course of at least an hour, without a big gap in between the pictures. I'll strongly recommend a DSLR in combination with a programmable cable remote (Vello Shutterboss Version II for around 50$). This will enable you to set the camera up and then let it work without you sitting just next to it all the time.
To get the landscape and a whole array of stars into the final image, a fairly wide-angle lens would be a good bet. My example was shot at 24mm on a full-frame camera, which would be around 16mm on a Crop-Camera. Just anything that enables you to get an interesting foreground and a good part of the sky in the frame.
Of course, the camera will need to stay in exactly the same spot for a long time, so a good tripod is really important. My tip with this: Get a good one in the beginning, as buying ONE good one is better in the end than getting multiple cheap ones that you'll never be satisfied with...
Shooting at night can be extremely rewarding, because by using long exposure it is possible to capture images that the human eye can't see. It is amazing of how you can start to see the world around you differently when getting into long-exposure photography. Just take a look at the picture from Morocco!
OK, so now you are in a beautiful place and you wan't to try out the technique for getting startrails. To get that circular look of the starts, you will need to find out where north is, as the earth is rotating around it's axis with the northstar remaining in the same spot. If you're not very familiar with the stars, just use an iPhone app such as "Star Walk" or a compass to find Polaris (the north star). Try also to get a night with no moon in the sky, and of course it should have no clouds;)
In my example I had the camera set up in its spot well before sunset. That way it was possible to get a nice composition with enough light to notice any distractions.
Once the composition is found, go through the following steps to ensure the best possible result:
- make sure nobody will walk around with a bright flashlight once you've started shooting, and if available on your camera, close the ocular (viewfinder) hood
- set the lowest aperture (f/2.8 or maybe f/4) and focus on infinity, do that with Liveview where you're zoomed in all the way to focus on a very distant object (maybe you have the moon in your back where you can focus on) and then put the camera back on the tripod
- after focusing, set the autofocus to OFF!
- Make sure you can exchange the battery without taking the camera off the tripod and without moving it AT ALL
- Turn OFF the image preview
- Turn OFF long exposure noise reduction!!! (This is very important!)
- Turn OFF HIgh ISO noise reduction
- Set up the camera in Bulb mode, so you can use it with the remote control and be familiar with it's controls, also in the DARK
I usually get the first shots around 20 minutes after sunset, so there will be some remaing color in the sky from the blue hour together with enough light to get nice detail in the foreground. This is also the moment where there is still a couple of minutes in decent light to confirm the focus is set on the stars.
Advanced Tipp: at this time you can also get a shot focused on the foreground, just use Liveview to focus on the foreground with an aperture at around 5.6 to 8 to get a nice landscape image and afterwards put it back into the largest aperture and focus back onto the stars. Do this only if you know how to stack the images together with masks later on the computer.
Now comes the part where you will need to be careful:
My experience shows me that I usually get the best results by choosing an ISO value of 400 at f/4 with a exposure time of two minutes. That way with a dark sky the histogram will be around from a third to the middle across on the left side. I usually get a decent exposure of the stars with these parameters.
The reason I choose ISO 400 instead of 100 is that I can shorten the exposure time from 8 minutes to 2 minutes. In modern cameras, the increase in noise by using ISO 400 is neglectable, whereas it increases the longer you expose, just because the sensor heats up during the minutes it is powered. I couldn't yet find noticeable noise up to two minutes, but afterwards it starts showing up.
Try to remember: If you need to change a parameter after you have started, ONLY change the exposure time, as a different aperture or ISO will give a different luminance in the stars. A longer exposure will just lengthen the distance a star moves and brighten the surrounding, but it will not affect the stars itself. And that is important for a homogenous image in the end.
Set the remote-shutter-release up for continuous shooting of 2 minute exposures with about 1 or 2 seconds (not more) pauses in between. This pause should be as short as possible to reduce any gaps in the moving stars, but long enough to enable the camera to react for the next shutter release.
Now just let the camera work for some time. As the earth moves around 360 degrees in one day, it will rotate around it's axis 15 degrees per hour, so a single star will move 15 degrees around polaris per hour (1/24 of a full circle). It is up to you for how long you want those trails. I like something between 1.5 to 2 hours, as in the example image.
Of course it is not necessary to sit beside the camera all the time, but make sure you check it regularly, as the continuous exposing will drain the battery quicker than you're used to.
Just make sure you don't use a flashlight anywhere near the camera, as any light will somehow find its way onto the sensor and create some weird artifacts on the final picture.
Ok, now you are back home in the warmth an you have a ton of two minute exposures, each one not looking really artsy.
My Workflow looks like this:
I import all the images into Adobe Lightroom into a separate album. I make sure I have only images in this album where no break or pause bigger than a couple of seconds was in between, this makes sure I can add them all together and not get a noticeable gap between the startrails.
I use a random picture of the series and develop it in the basics panel in the development module. Set the white-balance, raise a little contrast, set a white and a black point, just regular image optimization to get the stars pop out a little more.
Once I am satisfied with the edits, I select all the images from the shoot in the overview below, make sure I am still viewing the edited picture, and hit the Sync... Button. This syncs all the development changes from the active picture to all selected ones.
To add all the images together, you can use Photoshop, but it is easier to use StarStax. It is a free software, but consider making a contribution if you like the software and if you're using it regularly.
There is a great manual on the website, but it's actually really easy to use.
Just export all the images from Lightroom into a folder as TIFFs, and drag&drop those then into StarStax.
Select "Gap Filling" under the Blending option and let the software do it's magic.
Once done, save it again and go back into Lightroom for some final image editing. This is depending on your own habits and taste, so I will not go into it further.
Please check back for new tipps and tricks or leave a comment below.
Also let me know if you have an idea for a new tutorial