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How to shoot the stars and the Milky Way – 500 rule

By March 26, 2015 5 Comments

How to shoot the stars and the Milky Way – 500 rule.

After my recent release of my milky way shot at Marken, I got several questions on how I did it and what settings I used to get the photo.
For this photo I had planned a lot. I scouted the location (using google earth and other photo’s on 500px) and checked when the milky way was in the right place for the look that I wanted.
Next thing I needed was a clear night.
Last week we had 1 clear night, so I headed of to the location (which includes a 35 min walk towards the lighthouse) and took the photos.

Here I will give you some tips on how to photograph the night sky.
Getting the right exposure is all dependent on the combination of your lens (max aperture) and the camera sensor (how well does it perform in low light).
Most important, you will have to shoot in manual mode!

Here are the things to consider:

Dark surroundings

The darker, the better.
Where I live we don’t have a lot of dark sky around us. And as you can see you will still be able to take a decent photo of the stars, but if it was pitch black……
Try to go somewhere where the light pollution is minimal or at least low on the horizon.

How to get sharp star photos?

Due to the rotation of the Earth, it appears as though the stars are moving through the sky in long exposures. Star trails can be a desired effect when done for much longer exposures or stacked exposures, but in other cases we want points of light to represent how we see the stars with our eyes. To achieve crisp stars you can use a simple rule that’s often called the “500 Rule”.

500 Divided By the Focal Length of Your Lens = The Longest Exposure (in Seconds) 

And this is for full frame camera’s. For the crop sensor camera’s, take into account the crop factor.
An example:

I used 16mm as my focal length and I’m on a full frame camera.
So the longest exposure time I could use is: 500/16=31 seconds
If you are on a crop sensor camera from NIKON you divide this by 1.5 and for CANON you divide this by 1.6.
So if you are shooting with a Nikon D3300 for example your max exposure time is: 500/16=32 /1.5=21 seconds
If you where shooting with a Canon 7D: 500/16=32 /1.6=20 seconds.

When you go over the maximum exposure time, you will start to get star trails.

 

Stable shooting platform

Next thing to consider is a really sturdy tripod and a remote release.
You don’t want any vibrations when you take your pictures, because that will blur the frame.
To reduce vibrations, use a really sturdy tripod.
Furthermore use mirror lock up or use live view. When you take the photo your mirror will flick up and the exposure starts.
By flipping up, the mirror causes the body to vibrate. When you select mirror lock up, the mirror flips up first and then you press the shutter again for the start of the exposure.
But when pressing the button, you introduce vibration once again.
The solution to that is to use a remote control (cable release). I personally prefer the combination of the amazing app and the cable release of Triggertrap.
I can  highly recommend Triggertrap. I’ve been using it for 2 years now, and wouldn’t be without one anymore.
You can have a look here: Triggertrap (if you use this link, you will help me and the site as well – would be awesome! )


Perseids meteors

Focusing

Focusing at night can be a pain.
First thing to do is to turn off auto focus, because it will be unable to focus correctly.
When you have live view on your camera, use that to focus on a bright star. Zoom in on the star and focus.
You could also use the infinity symbol on your lens to focus to infinity.
In my example, I focussed on the light in the lighthouse.

 

Lens

When taking astro photos a fast wide angle lens is the best, so you can get as much of the sky in one shot. An other possibility is to take a panorama and stitch them together in photoshop.
Anything below 24 mm will do.
With a fast lens I mean a lens with an aperture of f/4.0 or below. Normally f/2.8 is recommended because it will let more light hit your sensor than f/4.0.
But I only have an max aperture of f/4.0 and it will definitely do!

ISO

Here comes the big question on what is correct. This all depends on your camera.
There are some low light monsters out there that won’t produce a lot of noise on high ISO’s, but for the most a good starting point is ISO 3200. 

Take a test shot with the wides aperture (lowest f number) and set the shutter speed according the 500 rule. Then set the ISO to 3200 and take the shot.
Have a look at your photo. Too dark? You can add 2 seconds to your exposure or select a higher ISO. Also take a look at your histogram. If the photo looks dark but there are no shadows clipping in the histogram, it’s ok. You can get more out of the photo during post processing.
Especially if your camera is producing a lot of digital noise on your photo with an ISO of 3200 or higher.

 

To sum up:

  • dark surroundings (it can be done elsewhere but you will have to do a lot in post processing)
  • fast wide angle lens (preferably f/2.8 but f/4.0 will do)
  • focus using live view or the infinity mark on your lens
  • maximum exposure according the 500 rule
  • ISO 3200

 

 

 

 

Happy shooting and please share your photos in the comments!
If you need feedback on your photos or want to know how to improve them, please leave a reply.

 

 

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