![]() So in the series of shorter photos - each perhaps 30 seconds long - in every shot you can collect enough total light that the surroundings have become correctly (maximally) exposed, while the stars have barely moved anywhere, making them quite bright. The second advantage of combining a series of shorter photos is that it lets the stars appear much brighter: This is basically because during a long, slow exposure where the camera's collected just enough light such that the surrounding scene bas become correctly exposed (and any 'light pollution' not yet bright enough to be problematic), the accumulated brightness of any given star is actually spread out / divided along it's whole path, whereas if the star had stayed in the same location that whole time (as it appears to when the overall light collection is accelerated into a shorter photo), it's gathered brightness just compounds in the one spot making it brighter and brighter. Taking lots of shorter photos instead (and we can get the camera to do this for us), alleviates this problem. This means that for lengthy exposures, the longer the shot is, the lower quality it will be. The problem is that the camera's sensor is just like any other electrical device, and it gets hot if you leave it running for too long, and this heat creates an ever increasing amount of random speckles of colour/light to register throughout your image, called 'hot pixels' (the effect looks similar to ISO noise). Basically, taking one long exposure is a hell of a lot easier to do, but has some significant drawbacks. Tricky question, and different people swear by different methods. ![]() Take one long exposure, or lots of shorter ones and stack them together later? While we're messing about with the lens, now's also a good time to turn lens stabilising OFF if you have it (unusual on a wide lens anyway) because it'll chew through your batteries on a long star photo! If you really can't get AF to latch onto anything, then switch it to MF and if your lens has a physical display/ruler showing the focus distance then rotate your focus-ring until it's set it to the infinity mark, or if it doesn't have one then fine, go and squint through your camera at the night sky and rotate your focus ring back an forth until the stars look as sharp as you can. After it's managed to *beep* and latch onto something with AF, then take your finger off, find the Manual Focus (MF) switch (usually on the side of your lens) and switch your lens to MF and then you're good to go - now just remember not to bump that autofocus ring (or the zoom ring either as on some lenses changing zoom affects focus, so it might be best to set how wide you want to zoom first). It helps to set your camera to use only its centre auto-focus point so you can precisely select what to focus on. Yes you usually can actually Auto Focus (AF) at night, providing you accurately point at a star that's bright enough, or at something like the moon, or failing these, on a point light source on the horizon somewhere - its all about the same distance away as far as your camera's concerned. Don't let all these ideals dissuade you though, you can still have fun and get some pretty cool shots in your backyard, in town.īefore you get tangled atop tripods, get your focus sorted first. I think the best star trail shots are ones with something interesting framing up the foreground, so perhaps near some impressive trees and an old shed or something. Another point to consider when picking your location is what to have in your foreground. Also it's best to shoot from somewhere where there's less chance of a car, a torch-wielding person, or even a plane accidentally ruining your shot. ![]() Of course you need a clear, cloudless night, and ideally a dry (not humid) night too, else condensation may form on your lens (some people literally wrap those little hand-warmers around the lens to keep it warm to prevent this). The moon too adds significant light pollution so shooting during a 'new moon' (no moon) is ideal, or when the moon has set below the horizon, or at the very least, is well out of shot (and won't move in!). You really can try this anywhere, but you'll find that if you're too close to town, then the 'light pollution' that emanates from civilisation makes it harder to see the stars, so rather than being nice and black, the background to your stars will become a pale haze instead, and this also means you won't be able to take as long a photo (ie such long trails) before it becomes completely washed out.
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