The Christmas Star?

I have always loved the night sky, I think most people would say the same thing. I consider myself fortunate enough to live in a rural Manitoba, in the small City of Morden. Only a short drive out of the city and you lose most of the light pollution that people living in larger urban centres have to deal with. Drive a half hour and I’m on the edge of some of the darkest skies around. This however was not the dark sky sort of night. The moon was at about a quarter moon and I decided to try a tracked, stacked & composite image.

Say what!?! Tracked. Stacked & Composite! So let me explain what’s going on here. This is really using multiple techniques to create on final image. Let me start off by saying that I will never create an image that isn’t real, that is I won’t put stars where there aren’t any or add a moon into an image that didn’t exist, or if I did I would very clearly label it as such, because I don’t believe that it is really true photography anymore as much as it is a digital composite. Anyway… lets get back to this image. So going out, I had this image in mind, and this is how I went about creating it.

First off I shot 4 images of the scene with the camera on a tripod of course. I was shooting with a Nikon 16-35 f/4 lens, with settings of 15 seconds @ f/5.6 and 6400 iso. This captured the foreground image, but why 4 images? Well in the computer you stack the 4 images with a median blend mode in photoshop, this removes or reduces the noise from a high iso image. Ok so we now we’ve got the base image captured, and the moon was right there over the barn and the image did capture the stars in the sky, but 15 secs is the very limit you can shoot with and still get relatively pinpoint stars, so this is where the Skywatcher Star-Adventurer star tracker comes into play. I then mounted the camera on a star tracker. This is a mount that tracks the stars and allows you to get much longer exposure times. So for the sky I shot only 5 images again with the Nikon 16-35 f/4 lens, shooting at 120 secs @ f/5.6 and 400 iso. Now if you do the math that would capture less light then my original exposure, however stacking 5 images shot like this allows you to pull A LOT of data out of the image and shooting at a low iso like 400 you retain a beautifully smooth, clean sky with amazing pinpoint stars. So there’s your stacked and tracked portion of the image.

All that was left after this was the composite, that’s where you brought together the sky from the tracked image (the ground gets blurred) and the still image of the barn in the foreground. Blending these two images together gives you a very accurate representation of the scene that existed and was impossible to capture with that clarity in a single image. Oh I didn’t mention that I also incorporated a technique known as Low Level Lighting to light the barn during the initial exposure, I’ll touch more on that in the future.

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