Hey Everyone
I have been getting asked a lot lately how I did the star trails, well I decided to share the knowledge. Now all I did was Google "star trails" and filtered through the links until I got a good idea on how to do it, however there was still some trial and error.
We will start off with a equipment list:
1. Tripod
2. Cable trigger
3. High powered flashlight
4. Fully charged battery, or a way to hook up AC power
5. Camera (obviously)
6. Wide Lens
Now that you have the gear you need a location, now the location is important for many reasons. Most importantly light pollution, you need to be far enough away from any ambient light sources so that the constant light does not over expose your shot. For major cities like Calgary you need to be at least 100km away remember the camera is more sensitive to light then our eyes, the bigger the city the farther away you need to be. Now there are two methods to doing star trails and one will allow you to shot with a bit of ambient light but you need to be careful on how much. Oh and be careful of traffic my first attempt was squashed because of big rig trucks passing through my image and getting the lights streaking across.
Ok so now you have your gear and a location, this is where it starts, first off composition of the shot. There are two types of trails the way I see it "Just Stars" and "Anchored Trails" meaning you can either shoot just the stars themselves or you can use a tree, building, bridge, landscape, etc to anchor the image (This is where the flashlight is used but I will get to that shortly). So you go for an anchored imaged you pick a tree lets say, set up your tripod low to the ground this way you can angle the camera higher in the air but still get some of the tree tops.
Now we get technical
Method 1: (easiest way, but a lot of post work)
Focus on the tree tops (use the flashlight to help) ISO I use 400, F/4-5.6, shutter speed is the key here and why you need a tripod. The entire secret to star trails is this...you ready...we are moving...thats it. What I mean is the earth is rotate as we all know and just like the sun and the moon cross the sky the stars do to, now to catch the stars movement you need a long shutter speed you begin to see the movement after a 15 sec exposure best results come from a 30 sec exposure, be sure to turn off any NR (noise reduction) on your camera both High ISO and Long Exposure NR, this slows down the camera and puts too much time between images.
Now based on your ambient light you can adjust the Fstop to correct for the image brightness. Just a couple more settings and you are ready to shoot, take the camera and set the shooting to high speed, most pro-consumer and pro dslr have a little wheel on the top left of the body that allows you to change the frame rate of the camera, so ramp it up. Also attach the remote trigger, this is a key step because it is the only way you can set the camera to shoot back to back images without moving the camera and or taking too long between images to shoot.
This is a BIG point I need to make you are going to take around 100-200 images back to back any more than half a second between images you will begin to get a dotted line when you composite the images. Trust me I found this out the hard way 3 hours gone...lol oh yeah this takes a while plan to be out most of you night between the hours of 1am-4am when the sun is totally gone this is where bankers hours don't apply.
So you are set hit the remote trigger so that it is "locked" at let the camera do the rest. You should be able to hear the shutter open for 30sec, then close and re-open immediately, it sounds like..... click.....................clickclick..................
This image was multi image, looking straight into the sky.
Sit back relax, I usually set up so my car is close to the camera because it gets cold out here at night. Now a couple of issues to be careful about battery life it drops drastically when the batteries get cold not to mention the long shutter exposures of time drain the battery, so if you are worried about battery life try getting a AC power cable for the camera. This is how I do it and why I have my car near by, I picked up a cheap inverter and a long extension cord so that I fun the camera off my car battery, works like a charm.
The other issue is condensation or fog on the lens, if you took your from a warm environment to a cold you may get crystals on the lens or from a cold to a warm environment you may get fog on the lens, or if the outside temp goes from cool to warm in a decently fast rate you will get fog. Best way to solve this (don't touch the camera now) a hair dryer, just periodically check on the camera lens to see if you are all good.
Ok you are almost done, the last two frames are important, remember the tree so far you should not be able to see it in any of the images because you are only exposing for the stars, but your second last frame you need to take that flashlight I mentioned and "paint" the tree with the light for the entire 30 seconds be sure to be even and cover the whole tree, the image you should get will be the stars and the tree. If worked out, put the lens cap on and take another 30 sec exposure this image when added will take away some of the noise in the image because of us turning of the NR.
By the time it's done you should have around 100-200 images like I said. So what now? Go home and sleep!
Ok so the next day your load your images name them, don't modify any of them if you shot raw leave them as is. You have 200 images what now? Run photoshop and use the script tool under file use "load images into a stack" this I didn't know about for a long time and it took me hours to do the work the computer did for me in 20 minutes. Pick the folder of the images and say go, make sure photoshop is the only program running because this takes a lot of processing and the file gets big. Go have lunch or watch TV, when the composite is done SAVE IT right away.
We have a psd file with 200 layers but you only see the top layer thats perfect...your done...kidding... you need to blend the layers don't worry it's so simple. On the layers palette there is a drop down menu that says "normal" click it... the drop down should have "lighten" midway down select it, and you should see the layer underneath the one you are on appear and the star trail should grown just a bit Now this is where you find out if all the hard work and time paid off. If there is a gap you will see it or if the camera moved you will see it so cross your fingers your all good. Do the layer adjustment to every layer but the last and the image is formed.
Once you have the image now you can make adjustments to colour, exposure, contrast, etc.
Side Note: With this method you can actually make short time lapse clip that will show the stars moving it will only be like 4 seconds but it's a bonus.
Ok so there is method 1, method two is a little more simple but just as time consuming and risky.
Method 2: ( 4 hour long exposure)
Ok same rules apply but are a little more enforced here. Ambient light, you need 0 of it your exposure is going to be 4 hours long any light pollution with completely screw you.
Camera movement big no no the image will become blurred and you will loose sharpness.
Remote trigger and settings, set the camera at ISO 100 and a wide Fstop 2.8 or as low as you can go, set the exposure time to "bulb" most pro cameras and some pro-consumer cameras have this ability. Use the remote and "lock" it. Now because there is a certain amount of light out in the wild as you will find as you notice at first you cant see jack when you are out there but eventually your eyes adjust and you can see almost everything. The camera does the same the camera after hours can see most objects not perfectly but edges you can help by using the flashlight near the end of the exposure last 30sec or so and "paint" your scene.
The camera should now be set it should be going and with any luck, no light, and no batteries dying 4 hours later you should have your star trail... This is a one shot one kill deal, if you don't get it, your night is usually done because the sun starts to rise. The plus side is you don't have 200 images to sort through...
A few last tips, be sure to know sunset and sunrise times, this will help you not mess up, also know what moon is out, you do not want a full moon it causes too much light pollution. A new moon or crescent moon are the best. If you see a streak in your image you got the moon on the shot, if you do the multi image method its not a big deal, also if you have a random streak in your long exposure method you caught a shooting star...BONUS...
This Image I used the multi image method, shining my headlights in the last frame
Points of axis, if you want a axis in your image like I have above you need to know which way is north find the big dipper and join the last two stars in a line to the tail of the little dipper. That first star never moves and its the North axis, kinda cool to know that if there were a straight line from that star to earth it would go right to the North Pole...
I really hope this was not to long and I hope it was helpful.
David Wilder
info@davidwilder.ca
www.davidwilder.ca
www.twitter.com/david_wilder
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