Astro Photography


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What Is Astrophotography?

Simply put, it’s a specialized kind of photography. One comprised of concepts and techniques that involve the photography of astronomical objects. These might be the moon, planets, and stars, but also nebulae and The Milky Way.

Types of Astrophotography


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There are several types of astrophotography you can pursue. Our article will go through all of them.

Deep Space/Sky

Photographs that were taken with a telescope of objects far away into the night sky. These are the beautiful images of interesting nebulae and distant galaxies. This style would include the most complicated and technical aspects of astrophotography.
Here, you need to think about star trails as a challenge to overcome. Also, having to think about telescopes, light pollution, editing software and other pieces of equipment.

Solar System

Everything within our own solar system, such as our moon, our sun and the planets that circle around it. Here you can use a telescope, but you can also use a multitude of telephoto lenses to get stunning results.

Wide Angle Astrophotography

This is a type of astrophotography that uses a wide field of view, such as wide and super wide lenses. These images include night landscapes with the Milky Way in the background, adding definition into the sky. Capturing star trails is also another great subject. This area is very accessible and the least technical.

Time-Lapse Astrophotography

Time-lapse is an extension of the wide angled astrophotography. This requires you to take many exposures over a period of time and then combine the images to create a video. This is also a great technique for star trail images.

Choosing the Best In-Camera Settings

Manual mode is a must, and that goes with your focusing too. You need to do it all yourself.
The last thing you want, during a 105-second exposure, is for your camera to decide the scene isn’t sharp enough and tries to re-focus.
Shooting in raw is a must, as that captures the most amount of information for post-processing.
Another benefit that is often overlooked is ‘mirror-lockup’. This is a setting on most DSLRs that stops mirror shake.
The mirror flicks up and down at the start and end of each photograph. This can really create problems in your astrophotography.
Set your white balance to daylight for easier tweaking in post-processing, saving you time.

Aperture

One luxury of focusing at a single point of interest, millions of miles away, is that you don’t need to think about the depth of field. Even if you shoot at f/1.2.
So the question isn’t ‘Will everything be in focus’, it’s ‘Will I have enough light for my exposure’. After all, we capture photos of the stars during the darkest nights of the month.
For Milky Way photography, I recommend shooting at your widest aperture settings—f/2.8, for example. This will allow the most amount of light into the lens, and allow for a shorter exposure duration.
If you’re taking a photo where you include some foreground interest in the frame, such as the tree in the image below, then f/2.8 is the magic spot. It’s just wide enough to allow plenty of light into the lens while providing a deep enough depth of field to get the foreground in relative focus too.


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Shutter Speed

If the aperture you choose for Milky Way photography is the widest possible, then the shutter speed should be the longest possible.
But how long is the longest possible?
We can set almost limitless exposures on our cameras. But there’s a very specific limit to how long you can expose for photos of the stars.
Set too long of a time, and the stars will start to move in the sky and those sharp dots of detail will look like soft smudges.
Fortunately, there’s a very easy way to work this out with a quick calculation involving your focal length, called…

The 500 Rule

The 500 Rule calculates the longest exposure time possible for Milky Way photography without capturing movement in the stars.
It does this by taking the number 500 and dividing it by the focal length of the lens you’re using.
For example, 500 divided by 14mm would be 35.7; this means 35.7 seconds is your maximum exposure length.
For that same calculation again, this time for a 24mm lens, the result is 20 seconds.
The reason for this is because when you zoom in, the you notice movement much faster. If you took a photo at 300mm on your lens at 1/50 of a second, it would be almost impossible to hold the camera steady and not detect any motion blur. But if you were to take the same photo at 24mm, it’s very easy to capture a sharp photo.
So the wider your lens is, the more time you have to expose for the stars.
There is one small caveat though, and that’s for people not using full frame cameras.
If you’re using a crop sensor camera, then your smaller sensor effectively magnifies the scene. It does so by cropping it.
So if you’re shooting with a Canon crop sensor, you would want to divide that final number by 1.6. If you’re using another model, you would divide it by 1.5.
For example, if you had a 14mm f/2.8 lens, but you put it on a Canon crop sensor body (like a Digital Rebel or a 70D), you would divide 35.7 seconds by 1.6 for a 22.3 second exposure time. If you were shooting on a Nikon crop sensor (like a D5000), you would divide 35.7 seconds by 1.5 for a 23.8 second exposure time.
All you have to remember is that you take 500, divide it by your focal length. And if you’re on a crop sensor camera, divide that number again by the magnification factor.


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ISO

Unlike aperture and shutter speed, there are no rules on what you can set the ISO to. It’s always important to remember that the higher the ISO, the noisier the image will be.
Using a full frame camera, you will quite easily get away with setting your ISO to only 3200. But if you have to compromises due to your sensor size, or your lens, then I would recommend an ISO for 6400.
Any higher than that will show too much degradation in the image quality. At that point, you’re probably better off pushing it in post-production.


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Focusing

Focusing on the Milky Way is super simple.
All you need to do is to set your focus at infinity, which looks like the figure eight symbol in the image below:
Milky Way Photography Settings: Focus Settings
On Canon cameras you want to line up the little sideways L with the line to focus on infinity. On other cameras you’ll want to align the infinity symbol with the line, so always check to see how it works on your lens.
Once you’ve set your focus to infinity, turn your focus mode to manual focus. This way, your camera won’t try to refocus in the dark when you go to take a photo. It will not do a good job!
Remember also to check your focus every time you recompose your shots. It’s very easy to knock the focus ring and send your photo into a blur.


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In-Camera Long Exposure Noise Reduction

A useful, but time consuming function of digital cameras is In-Camera Long Exposure Noise Reduction.
The camera does this by first taking a regular 30-second exposure. Once that’s captured, the camera will close the shutter and capture another 30-second ‘blank’ exposure. The camera will then compare the blank exposure to the original photo, to identify the digital noise, and then remove it from the original photo.
And it does a pretty good job!
But as with everything to do with exposure, there is one major downside: time.
This process is very time consuming and will drain your battery life, so it’s not perfect. And if you’re taking a bunch of photos for a panorama, it simply won’t be quick enough to capture photos without the stars moving too much to stitch together later.
Our Go-To Settings


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These are the settings we use for 98% of our Milky Way photography.
They’re specific to our gear. But once you’ve worked out what the settings are for your gear, you’ll find that you can also use the same settings for the majority of your shots.
Here they are:

    Focal Length: 14mm
    Aperture: f/2.8
    Shutter Speed: 30 seconds
    ISO: 3200
    Focus: Manually set to infinity
    In Camera Long Exposure Noise Reduction: Off

How to Shoot Powerful Astro Photographs

Photographing the sky sounds easy. You take your DSLR with a wide-angle lens out somewhere in the wilderness and plonk it on top of a tripod.
With everything set to manual, you point your camera/tripod combo at the sky and fire off a few photographs. You use the settings you worked out with the 500 rule.
And yet, this is deceiving. Astrophotography is not, in fact, that simple. You need a great many more things to turn that photograph into a breathtaking image.
Nothing good ever comes easy.
You need a good location, the right gear and an idea of what your subject is going to be. You need to research what is possible and look at many photographs for inspiration.
Even after photographing the scene, you need to edit the images too. Post-processing is another art, which will take time, effort and patience.
But don’t get discouraged! Keep reading our article, stick with astrophotography and the benefits will come tenfold.


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Written by ,

Craig Hull

Referance From :

https://expertphotography.com/the-complete-guide-to-astrophotography-89-tips/