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Picking A Lens for Night Sky Photography – Complete Guide

Photographing the night sky and the Milky Way is not as easy as photographing a sunny landscape, but with the right gear, it is definitely achievable! If you are on this page, I suppose you already have a DSLR and a good tripod, and you are looking for the best lens for night sky photography you can get today.

I love taking pictures of the sky when I travel, and I know I took a while to get the right equipment. So I made this little guide to help you choose a lens that will be great for astrophotography or Milky Way photography. The guide highlights the factors to take into consideration to make your choice and pick the lens that is just right for you, and I will tell you what lens I am personally using.

Without further ado, let’s dive in!

What Are The Factors to Consider Before Choosing A Night Sky Lens?

Night sky photography, or astrophotography, is a type of photography that really pushes the limits of the equipment and you need a lens that is perfectly adapted to low light. Let’s see what are the most important factors to consider when you are choosing an astrophotography lens:

Compatible Formats

I will evacuate this obvious one quickly. Some lenses are compatible with full-frame cameras or only APS-C cameras (crop sensors). Make sure you double-check that the lens you are about to buy works with your camera!

Focal Length

The focal length determines how wide the angle is. For night sky photography, we often like to include an element of landscape with a large portion of the starry sky. As a result, just like for simple landscape photography, it is best to choose a wide-angle lens.

Remember that when you are using an APS-C camera you need to take the crop factor into consideration (around 1.5x) and the field of view will actually be smaller.

Maximum Aperture

This is a crucial point for astrophotography. Since it obviously takes place in very low light conditions, the lighter your lens can let in to hit the sensor, the better. An aperture of f/2.8 is good and anything larger than that (smaller f-numbers) is excellent.

Other “large” apertures such as f/3.5 or f/4 may be OK for general low light conditions, but they are not enough for astrophotography. All lenses listed here have an aperture of at least f/2.8 and are well suited for night sky photography. You can see the next question for more information about aperture.

Optics Quality

This is extremely important as well because in night sky photography you will be using your lens at its largest aperture and it needs to be good enough to maintain good image quality and a good sharpness even at that large aperture. You need to also make sure your future lens is not subject to chromatic aberration or flare.

Autofocus

For night sky photography, this is not a crucial factor in my opinion. The autofocus systems struggle to detect and focus on the very low light of the stars, and you are better off using manual focus and just setting your lens to focus on infinity to be sure the stars (and the landscape) are sharp.

Image Stabilization

Same thing, this is not a factor I would consider for astrophotography because it involves long exposures on a tripod that needs to be 100% stable and this should result in sharp images whether you have stabilization or not.

f/2.8 vs. f/2 vs. f/1.8 vs. f/1.4 – Does It Make a Big Difference?

Well, yes, kind of.

These numbers represent the maximum aperture of the lens: how much light it can let in. Aperture is measured in “f-stops” and goes from f/1.4 to f/2, to f/2.8, to f/4, and so on. The smaller the number the larger the aperture. You noticed that I skipped f/1.8, it is only 2/3 of a stop larger than f/1.4.

So how does it work? The principle is that from an f-number to the following (one full stop of light) the amount of light that is captured by the lens is doubled. So a lens open at f/2 is twice as bright as a lens open at f/2.8. And an aperture of f/1.4 is again twice as large as f/2. So the difference is truly significant!

In practice, it is advantageous to have larger apertures because you can afford to use a faster shutter speed and a lower ISO to get the same exposure. In astrophotography, the most relevant advantage is ISO.

In order to take a picture of the very dim light of the stars, we often need to use a very high ISO such as 3200 or 6400. Depending on the camera you are using, this results in more noisy images – which is of course something we want to avoid. A larger aperture allows us to use a lower ISO setting and preserve image quality.

That said, some lenses with extremely large apertures get a little soft (in the focus) when fully opened. And well, even if the brighter the better, I think that any aperture from f/2.8 and larger is just fine for night sky photography. Any lens selected on this page is just fine. I would definitely not go for a smaller aperture than f/2.8 though.

What Lens Did I Get?

It is always a little delicate to choose a top pick. You may or may not agree with me on what is the best lens on the list, so I want to explain here how I go about selecting the top picks.

My goal is not necessarily to find the absolute best lens no matter how much it costs, or, on the opposite, to find the absolute cheapest price possible. My goal is to find the best value for money. My top picks can be rather cheap or rather expensive, but what matters is that they offer great features and great quality for a fair and justified price.

Here, I have personally bought the Rokinon 14 mm f/2.8 because I think it has the major features we are looking for here: a quite rare 14 mm focal length (meaning an ultra-wide angle), and a very large aperture of f/2.8. Moreover, the optics of this lens are really high quality and delivers beautiful, very sharp images. And this performance comes at a very affordable price. This is an amazing value for money if you can accept manual focus.

The Tokina 11-16 mm f/2.8 – is also a very popular choice for an APS-C camera, that’s a great focal length with a large aperture in a good quality lens, coming again at an affordable price.

Of course, just as with most things in life, the higher your budget, the higher-performance lens you canget.

Final Thoughts

There are many great lenses out there, but I believe that the information on this page will help you make the right choice, whether you have a limited budget or a more comfortable one.

I really hope that the information on this page was valuable to you and that this guide was helpful for you to decide what astrophotography lens you should buy.

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