“There are more things in heaven and earth, Horatio/ Than are dreamt of in your philosophy.” – Hamlet (1.5.167-8)
Foreword by Josh: This is a guest post written by Andrea Minoia, and we’re blown away by the depth and quality of his writing. This is by no means a quick and easy read (at nearly 4,000 words). But it is a hugely detailed guide to deep sky astrophotography. It covers absolutely everything you might possibly need to know to get started. Take notes, bookmark the page, and dive in…
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Astrophotography is a challenging and technical game. We want to keep things interesting and as easy as possible for you.
We will discuss editing techniques in another article. Here we’ll focus on how to take pictures of stars, camera settings for stars and night sky photography.
If you are a confirmed astrophotographer, this article will refresh your knowledge.
And if you’re a beginner? You’re about to embark on a fascinating journey among the stars.
This article will give you the basic principles you need. It will put you on the path to getting the best results. And using equipment you most likely already own, with few essential upgrades.
The DSLR Astrophotographer
People often believe that astrophotography requires the use of huge telescopes. Also, dedicated, cooled, astro cameras. That’s true if you want to do planetary work, but we will not go into that in this article.
We are going to start with how to take pictures of stars. For most beginners, DSLR cameras with normal and telephoto lenses, are enough to start you off.
For the casual astrophotographer and beginner, night photography can be daunting. A simple setup with their equipment on a fixed tripod is enough.
Another advantage of this is that it’s hassle and maintenance free. You can concentrate on learning the basics of astrophotography. Without worrying too much about gear.
If you’re not careful, you can soon end up dealing with monsters like this. Astrophotography is quite an addiction.(Credit: Warren Landis )
It’s All About Size and Brightness
When it comes to how to take pictures of stars, distance is not important. Both the Moon and Andromeda galaxy are at “infinite” distance for practical purposes.
The Andromeda galaxy is 2.5 million light years away from us and has a radius of 110,000 light years. For comparison, our Sun is a mere 8 light-minutes away from us.
We cannot grasp the sheer enormity of those numbers. With a telescope, you will have to do a mosaic composition to image the whole galaxy.
To get a photo of Andromeda and its surroundings, a 400mm, 300mm or even 200mm telephoto lens will do the job. Having a lens like this is a step in the right direction on how to photograph stars.
The Andromeda galaxy (also known as M31) with its satellite galaxies M110 and M32. Photographed with a 50 year old, fully manual, 200mm f/4 telephoto lens on m43 camera (400mm EFL). // Shot of Andromeda galaxy photographed with a 50 years old, fully manual, 200mm f/4 telephoto lens
The bright “star” near the centre is Andromeda. This is how it appears in a raw image taken from a moderately light polluted location.
Targets for DSLR Astrophotographers
You don’t have to photograph planets. There is no shortage of targets for astrophotography.
There’s the Moon, Sun, constellations, stars and countless deep sky objects. You can keep yourself busy for many years to come.
We can even capture long exposure stars and Milky Way photography. Or shooting star photography and night sky photography in general.
The Moon and the Sun
You can capture the Moon and the Sun with a long telephoto lens. You don’t even need a tripod if you have image stabilisation.
Warning! DO NOT attempt to observe the Sun or photograph it without using a properly designed filter. They are cheap and will save your eyes and your gear.
This article deals with Moon and Sun photography in detail. This is a great place to start in how to take night sky photos.
Stars and Star Clusters
Bright individual stars such as Sirius and Betelgeuse are nice targets. Especially if you have a long telephoto lens and teleconverter.
Some star pairs are famous. Pollux and Castor or Procyon and Gomeisa are some, where one star is orange (“cold”) and the other blue (“hot”).
Procyon (bottom right) is the eighth-brightest star in the night sky. The Yellow star is Gomeisa. Both stars are in the Canis Minor Constellation.
Clusters of stars are nice too and the most famous in the Northern sky is the open cluster of the Pleiades (or M45).
This is a region of bright, hot (hence the blue color) and young stars soaked in dust clouds. This gives the Pleiades the classic blue nebulosity.
This cluster is very bright (apparent magnitude 1.6) and large (apparent size of about 2º). You can spot it from a large city.
Constellations and Star Fields
With a wide angle lens you can photograph constellations. Or the Milky Way shining over a landscape. I discussed this in this article.
In this image I have sketched in red the full Orion Constellation. If you consider the image captured with a fisheye lens, you can have a good idea of how big this constellation is.
You can also photograph constellations as part of wide star fields. The aim here is to capture the many nebulae and dust clouds that are part of the constellation.
If you are in the Northern hemisphere, one of the best targets is the Orion Constellation. Its shape is so unique that you can see it high in the winter sky.
This is thanks to the three stars in line forming the belt of Orion. This constellation is a great place to start in how to take pictures of stars.
This is a very complex and rich region, with plenty of bright nebulae. There’s the famous Orion Nebula (M42). And then the Flame Nebula, Horsehead Nebula, Running Man Nebula and Barnard’s Loop.
It also contains the bright and colourful stars of Betelgeuse (red) and Rigel (blue). And on the right of Rigel there is the darker Witch Head Nebula. On the left of Betelgeuse there is the Rosette Nebula.
My first serious attempt photographing the Orion Constellation. All the main stars are visible as well as M42 and the Flame and Horsehead nebulae.
With a 300mm lens on a full frame camera, you can close in on the belt and sword of the Orion constellation. Like this you’ll get a family portrait of the Orion, Running Man, Flame and Horsehead Nebulae.
Other great targets are Auriga. This contains the Flaming Star Nebula, and the dense region of Deneb (here below).
You can see the bright North America and Pelican Nebulae in the Cygnus Constellation.
Finally, we have the star field containing the Pleiades and the California Nebula.
There are many galaxies you can photograph. The easiest one is Andromeda and its M110 and M32 satellite galaxies.
The Pinwheel Galaxy and Triangulum Galaxy are bright. You can capture them without a telescope. They will be rather small in the field of view of a telephoto lens on a DSLR camera though.
Andromeda photographed with a 200mm lens on m43 camera (400mm EFL).
Nebulae are the most colourful and photogenic subjects up there. You can find bright emission nebulae everywhere in the sky.
Notable examples are:
1. California Nebula. This nebula is bright and large enough to be an easy target even in light polluted skies.
2. Flame Nebula and Horsehead Nebula. These nebulae are near the leftmost star in the Orion Belt. Here I was able to photograph them in a somewhat polluted sky.
The Great Orion Nebula (M42). This is without any doubt the queen of the Nebulae. It is huge, it is bright and you can see it with the naked eye from a city.
You can find it in the sword of Orion and it appears as a coloured star to the unaided eye. But point your camera at it and you will be amazed.
Without a doubt, M42 should be your first target. You can photograph it with some details even on a fixed tripod or from the city.
M42 photographed few km away from Brussels city centre, the largest city in Belgium.
A famous catalogue of objects (both easy and less easy to photograph) is the Messier Catalog. This includes 110 deep sky objects, such as star clusters, nebulae and galaxies. You can use this for inspiration.
The Messier Catalog (photo by Michael A. Phillips, CC BY 4.0)
Some of the objects we’ve described here are not visible in the southern hemisphere. But there are other great objects such as Megellanic clouds.
Also, many of these targets are seasonal. Orion, for example, is not visible during the summer and so best photographed in the winter.
I recommend using a software like Stellarium to check your target’s visibility in the sky.
How to Do Night Sky Photography: Basic Rules
Now that you have an idea about what you can photograph, it is time to discuss how to do it.
An astrophotography session is not quick. Even experienced astrophotographers still need to set up their gear.
On top of this, they need to find and frame the target and get the star in focus.
And then you have to wait to get tens (or hundreds) of exposures of the same target before you move on.
It is a waiting game, but you can get busy doing star trails with another camera or stargazing.
Here is a 10 steps checklist for you to ensure you will go home with the best data to process:
You can also hang some weight to the tripod, to further stabilise it.
A child bucket filled with stones hanging with a bungee cord to the tripod is an easy solution to stabilise it.
Frame Your Target
How do you frame a target you can’t see? When you have to use a telephoto lens with a narrow field of view?
There are three ways:
Buy a (rather expensive) computerised GoTo mount. This has memorised the coordinates of many deep sky objects. Once you set it up, it will point the camera at the desired target;
Trial and error: try your best to frame your target. Exhausting at best;
Buy a cheap red dot star pointer and hot shoe adapter. This is is the perfect choice for beginners.
A red dot star pointer is usually shipped with any telescope. You can buy it with an adapter to mount it on the camera hot shoe.
The idea is simple. A laser hits the screen of the pointer so that a red dot becomes visible. This is then superposed to the unmagnified view of the sky.
The red dot on the finder’s screen and how the finder is mounted on the camera.
If you aligned the pointer, the dot superposed to a target should be more or less centred in the frame.
In the image below, I used my micro four-thirds camera with a 300mm lens to frame the moon.
The lens gives me a field of view of only 3.3ºx2.5º, which makes it difficult to find and frame the bright moon.
By superposing the red dot to the moon, I can find and centre it in the frame in no time.
Put your pointer on the camera hot shoe, and switch it on. Then, use the knobs to align it to your gear from time to time.
If you cannot see your target and you have no GoTo mounts, you have to become fluent in the star hopping technique.
Nothing keeps you from aiming your camera at a random direction in the sky. This is, in fact, how I took my first astro image, the one that opens this article.
If you want to know what you have photographed, you can upload your final image on Astrometry for free. This process is “plate solving”. It will return your image with annotations for all identified objects.
It turned out I had photographed the Deneb/Sadr region in the Cygnus Constellation. The North America Nebula is visible near the star S7Cyg, below Deneb.
This image consists of 30 images taken on a fixed tripod using my old Olympus Zuiko OM 50 f/1.4 on OM-D EM 10 m43 camera.
How to Focus on Stars
Even worst than framing an invisible target is focusing on stars.
There is nothing more frustrating than finding all your images are out of focus. And after a night spent in subzero temperatures.
This was supposed to be the Auriga Constellation.
To focus on the stars, forget your autofocus. Also don’t trust the infinite mark on your lens. Instead, use your live view at high magnification and frame a bright star.
The more you focus in, the smaller the star will become and more of the faintest stars will begin to come into view. Turn your focusing ring slowly back and forth to find the sweet spot.
The problem is that every time you touch the camera, the image will blur due to camera shake. This makes the whole process a bit random.
You can buy a Bahtinov mask, but I like DIY solutions when possible. Placing a kitchen sieve on the front of my lens will create diffraction spikes around the stars when the focus is good.
I found this method very reliable and fast. If you have difficulties to see the spikes on your live view, try to do your best to focus and take a test shot. When you see you have sharp diffraction spikes, your focus is good.
You can also mark the true infinite on your lens with a marker, to make the whole process even faster in the future. Use a bit of gaffer tape to lock down your focus.
That way you will not move it when, for example, you put a dew strip around your lens.
After having focused the image with my kitchen sieve, I put the dew strip on the lens and accidentally moved the lens out of focus.
Freezing The Stars
In night sky photography, except for star trails, you want to have stars like points of light. But stars move across the sky at, in average, about 15º/ hour because of Earth’s rotation.
That does not seem much when we stargaze. But consider that a 100mm lens on a full frame camera gives you a field of view of only about 20º x 15º.
This is how the sky will look after a 3 minute-long exposure.
There are only two ways to freeze those stars:
Take very short exposures on a fix tripod;
Use an equatorial mount. Rotate the camera around the celestial pole to counteract Earth’s rotation.
Astrophotography With a Fixed Tripod
On a fixed tripod you have to take very short exposures. A rule of thumb, also known as 500 rule, is the following:
ET= 500 /(FL*CF)
ET is the longest exposure time (in seconds) before stars trails can be seen. FL is the focal length and CF is the crop factor of your camera sensor.
My M43 camera has crop factor 2. With a 50mm lens I could expose for max 5 seconds before I start noticing the star trails.
Rules like the 400-500-600 are qualitative. I was able to expose the Orion Nebula for 3 seconds on a 150mm lens with decent results.
Look at the ISO invariant regime. Brightening your scene by 1 EV is comparable to shooting at a double ISO value in the first place.
So in the invariant regime, there is no “noise” advantage to shoot at higher ISO. And you will reduce your sensor’s performance by reducing the dynamic range you can capture.
You should find online which ISO values your camera is ISO invariant for. And you should use the lower ISO in this regime. This will maximise the dynamic range the sensor can capture without noise penalty.
You might find the cramped histogram in the top right-hand corner. The important thing to remember is not to clip the highlights.
Capture as Much Data as You Can
It should also be clear that rising the ISO will not let you collect more data. To do that, you have to expose longer and/or use a wider aperture.
We want to stack many images to improve the signal to noise ratio in the final image. As such, your exposure should be long enough to collect a good amount of data.
But not so long that you will clip the highlights, get oval-shaped star and trails or run into tracking issues.
Poor polar alignment, unstable gear and mount periodic errors can ruin your exposures.
If you do not track the sky with an equatorial mount, use the 500 rule and take as many photos as you can. If you can track, take a test shot of 30″/60″ and see how it looks like.
Unfortunately, there is no single setting that will fit all the situations. And, again, take as many images you can.
Before heading home, if you have time, take a few extra images with the lens cap on. These are dark frames and will be useful in post to improve the quality of your final image.
It is important that you take them at the end of your session, directly on location. Capture these at the same temperature as your images.
Photography Equipment For Astrophotography
As I said, you need a DSLR or mirrorless camera, but very good high ISO capabilities are not really important. What you need is some ISO invariant behaviour. Also, your camera must allow you to shoot in RAW format.
An entry-level model such as the Canon 1300D is usually good enough to start with.
This allows you to close in on targets with shorter and cheaper telephoto lenses than those with full frame cameras.
Finally, keep in mind that your camera will be pointing at the sky. A camera with an articulated LCD screen is preferable. You will be able to operate it more easily and comfortably.
You can check our post on best astrophotography cameras here.
You don’t need to have the latest pro-graded lens to do astrophotography. You will not need autofocus or in-lens/in-camera stabilisation.
I actually use old manual lenses from the film era.
What you need is a lens without too much chromatic aberration at relatively wide apertures.
This is where modern ED lenses and APO refractors using low dispersion glass often have an edge over many old legacy lenses.
A great way to check if you can use your lens in astrophotography is to search it on Astrobin. This is a great free site and image database you can even contribute to.
Finally, you should go for lenses that perform well with apertures in the range of f/2.8 to f/5.6 for deep sky astrophotography. Slower lenses require longer exposures and even more images for stacking.
Typical focal lengths for full frame camera are:
50mm for wide star field images;
135mm for closing in on small constellation or narrower star fields;
longer telephoto for nebulae and galaxies close-ups.
Teleconverters are used to extend your reach, but the will cost you some light. They are a good solution for Moon and Sun photography and for the brightest targets such the Orion Nebula and the Pleiades.
If you want to see how big a target will be in the field of view of your camera-lens system, you can use the free software Stellarium. Just insert the info for camera sensor and lens (telescope).
A word of advice. Don’t get stuck with filling the frame at all costs. Very long focal lengths and high magnifications are challenging. Cropping your image is perfectly acceptable in astrophotography.
Must Have Accessories
If you don’t have the luxury of doing night sky photography from your garden and have to backpack like me, you’ll be out in the field for a while. You’ll need to carry your gear and things to make your astro trips more comfortable. I prefer to use backpacks similar to those for mountaineers, such as those in the F-stop mountain series.
This is a short list of the essential accessories you should have with you:
A good camera backpack with some room for your stuff;
A lightweight equatorial mount with accessories is the first investment to consider to up the game. A classic compass is more reliable than the one on your smartphone and it is essential for a good polar alignment of the mount;
UHC and LPR filters (Baader, Hoya, etc.) to boost contrast in the images and fight light pollution;
But this guide will help you get started. We also have a useful glossary of astrophotography terms you can check here.
You’ll also be able to join the fantastic world of astrophotography with fewer headaches than I got when I started imaging the night sky.
Stay tuned for the next article on how to edit your data. In the meantime, grab your gear and get out there and play with the night sky.
A note from Josh, ExpertPhotography's Photographer-In-Chief:
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