how to photograph the night sky
celestrial photography, rule of 500 & more
Looking up at the night sky has always been a huge fascination of mine, especially seeing the same stars from a different part of the world and of course finding new stars to see.
Shooting with a DSLR or Mirrorless can be a little tricky but there are a few ways in which you can improve to start to get great images. Some cameras work better than others, so this isn’t necessarily a one size fits all scenario. Celestial photography does take a bit of practice to get it right, but it’s totally worth it so be prepared to have lots of trial and error while finding what works best. This isn’t to be rushed so grab a walkstool and some late super along to your favorite nighsky spot.
Some great settings to start with are below, but let’s also find a great location and use some maths to help us shoot some stars.
Aperture of around f/2.8 (wider the better), Shutter speed of about 15 seconds, ISO of 100-400. Start at ISO400 and work your way back as needed to minimize noise, ultimately we will head towards 1600 to 2000 ISO depending on your sensor performance.
Make sure you turn off any Low Noise Reduction and any Dynamic Range assistance your camera my have, some mirrorless cameras may need to have image stabilization turned off. Use a solid tripod as well.
FINDING A LOCATION
Light pollution and clouds are the enemy of night photographers, so you might need to jump into your car (or someone else’s) if you live near a large metropolis on a clear night. A great way to plan this trip out is using “Light Pollution Map – Dark Sky Finder Astro Tools” mobile phone app or using one of the well researched university maps on the internet. Google “Darksite Finder” http://darksitefinder.com and browse a location near you just note that since these sources are crowd sourced or provided free, their accuracy cannot be validated but I have found them to be pretty useful and mostly reliable in searching for clear skies.
Anywhere with a great coast position or the higher you can get, the better.
It’s highly recommended to do a few site visits before you go live, so you’re familiar with routes in and out of the dark, and if there is a park closing which could get you locked in or out at certain times. Also check that some national parks don’t allow commercial cameras or photography onsite, so ask before you head out as you may need to get a permit in advance. So research if you are going someplace unfamiliar to you
Don’t forget to pack a tripod, cable release, a torch with sufficient batteries, some bug spray, food (this will be a long evening)make sure your food is kept away in a lock bag in case you attract ant wildlife, and let someone know where you are going too.
The 500 Rule (of Thumb)
One common mistake that’s often made by pros, beginners and everything inbetween is when starting to shoot the nights sky; leaving the shutter open way too long causing star trails (more on that later).
Sometimes we like or want this effect but generally we don’t.
So how do you work around that issue of trails and overly bright sky, well we can start with a little bit of maths…….
500 divided by the focal length of your lens “Equal to” The longest exposure before stars trail in the final image.
While this rule isn’t set in stone it should give you the basis of how to start shooting the night sky with minimal, or at least next to zero trails. Depending on the camera you may want to try starting with 400 or 600 to divide by but start at 500 and see where that takes you, if you have a crop sensor then try the Rule of 400 first as that has a multiplier of 1.3 to 1.5 and will have a different result anyway.
So for instance, if you have a prime lens such as a 15mm (a popular lens for night sky shooters, one I like to use all the time) on a full frame camera. Try 500 divided by 15 = 33.3 seconds, you can be a little flexible here and attempt 30 to 34 seconds as a fine tune and depending on your kit. If you see trails then reduce your exposure time, if the scene gets a little dark then bump the ISO slightly to compensate.
Other lenses to try are a 24mm, 40-50mm as well.
Remember long exposure works best when you use a trigger or remote trigger, one tool I use all the time is the MIOPS remote trigger which can be fired off from a mobile phone. One advantage here is you can dial in the release seconds as you please rather than using a stopwatch and a release cable plus your camera will remain steady. There are many such devices on the market that do the same thing, but a wired release can equally do a great job.
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