Landscape Photography at Night with Stars as Points
Reflections in Yosemite, August 2016
Made with Starry Landscape Stacker 1.5.0 from 23 light frames.
Canon 5DS, Canon 11-24mm f/4L USM, 11mm, f/4, ISO 12800, 15 sec, f/4
Original image is 50 mega pixels.
Starry Landscape Stacker is a Mac app for making images of the night sky with stars as points and low-noise. It uses "stacking" or "image averaging" to combine a group of images that were captured in rapid succession with identical exposure settings and the camera in a fixed position. The result is an image with stars as points and much less noise than you could achieve with a single exposure.
The basic idea is to take several images (at least 10, more is better) with a high ISO setting (3200+) and short exposure time (< 20 sec) each one of which is noisy, and then average these images. The averaging process reduces the noise. The difficulty with this is that the stars are moving relative to the ground so you must separate the sky from the ground and align the stars before averaging. You can do this with image processing tools like Photoshop, but it is a slow and tedious process. Starry Landscape Stacker will do most of the work for you. Also, Starry Landscape Stacker does not simply average the images, it takes the median of the images after outlier elimination. This produces a much better result than simple averaging and automatically removes airplanes and some other artifacts. Starry Landscape Stacker can also do dark frame subtraction and flat-field compensation to further improve the image accuracy.
There is a useful review of stacking apps on the Night Photography Workshop website.
How to use Starry Landscape Stacker
Situations where special care or techniques might be needed include
Aligning Reflections Of Stars (as seen in the image above)
Feedback and other applications
If you have any questions or suggestions, contact the developer.
If you have an equatorial mount and are taking pictures with just sky and stars, please have a look at Starry Sky Stacker.
If you have been wondering about stacking images taken during the day have a look at Long Exposure Stacker. It is intended for generating images with the appearance of very long exposures (e.g., removing waves from the surface of water, softening waterfalls) without using a neutral density filter. It also significantly reduces noise, so a split neutral density filter may not be needed in high-contrast situations. Instead gradient filters and burning and dogging can be used in an image editor, often producing a better looking result than split neutral density filters.
100% crop from Reflections in Yosemite above--0.6% of the original.
Approximately 300 K pixels from the 50 M pixel image.