Stacking Stars in the City
The spinning stars above the city of St. John's. | Nikon D3 24-70
This is an image that I’ve had in mind for a while but hadn’t actually remembered to go shoot.
The trick with this is that you can’t just open the shutter for a long period of time, like 30 minutes for instance. Normally for a photo of the stars spinning this is how you’d achieve this effect. But in this case if you were to do that, the light pollution from the city would eventually over power the stars and you’d have nothing but a glow of city light and very few stars.
So how do we do this? Well to start you’re going to need either a body capable of interval shooting or a cable release with a shutter lock. Once you’ve got one of those, you’re going to need to shoot a LOT of images, all at the same settings, over the course of 20-30minutes or longer. The longer the more apparent the rotation. My settings tend to be about ISO200, f/2.8 and as I’m shooting MULTIPLE frames to combine them later via stacking, my shutter speed will vary based on the set up. With this one the shutter speed was quite high for star motion it was set so the city wouldn’t be overpowering frame to frame. In one individual frame, the star trails were barely visible. But once stacked and rendered, they popped!
Remember to turn off any post-image noise reduction processing on your camera or any other options which might cause delay between frames. A delay between frames will cause gaps in your photos and thus gaps in your star trails, you don’t want that… or do you? Like most things creative, done effectively gaps in your stair trails can be very cool.
Typically I try and keep Polaris — the north star — in the frame somewhere. The composition tends to work much better when the north star is acting as an anchor for the frame and works well to draw the eye in. With this photo to still have the city actually look like a city and not just an awkward glow at the bottom of a super wide angle frame I had to use a tighter focal length, which I think was around 24-30mm and I left room for some cropping in the end. If you want to quickly check your comp without waiting 30 seconds for the frame to stop shooting, just crank up the ISO to the highest your camera offers.
Once you’ve got your 100 or so images, each a long exposure, you’ll be combining them in Photoshop to form one image, like the one below. I’ll make my adjustments to a single image in Lightroom (wb, contrast, color shift, sat, vib, blacks, clarity, etc.) and sync them all to the same setting.
You can manually stack your images in Photoshop but I wouldn’t :-D. There’s lots of stacking software and actions out there:
Star Circle Academy – http://blog.starcircleacademy.com/2011/02/automated-stacking-of-star-trails-in-ps-cs5/ (photoshop action)
Keith’s Image Stacker – http://keithwiley.com/software/keithsImageStacker.shtml (mac only)
This image is made from 95 images, each 30 seconds in length at f/2.8 ISO200. Body: Nikon D3 and 24-70 lens, cropped to 8×10, shot from Cape Spear, Newfoundland
In this photo you can see the stars which make up the big dipper, planes landing at St. John’s International Airport (CYYT), a boat going out to sea, the car lights from Signal Hill, Fort Amherst and the East End of St. John’s.
