Astrophotography is a trending topic and close to the heart of nature lovers and those who like to spend time outdoors. Modern cameras are capable of shooting noise-free pictures at very high ISOs. The ability to capture clean images in low light (and hence at high ISO) is essential to shoot the Milky Way and other celestial objects. There are some nice spots in India where you can capture the night sky. Here is an astrophotography guide that explains what you need to get great night photos with any camera that can shoot in manual mode.
- Examples of Astrophotography
- Equipment for Astrophotography
- The three-step drill – Plan, Shoot, Process
Examples of Astrophotography
Astrophotography is a very broad term and can involve shooting a variety of celestial objects after dark. For most of us who do not own specialised equipment, astrophotography is limited to shooting star trails, the Milky Way and the moon. If you own, or have access to a star-tracker or a telescope, you can shoot deep sky objects which are much farther away in the heavens above. Capturing deep sky objects involves shooting multiple, long-exposure photographs through a tracking telescope and using advanced processing techniques to create the final image.
We will keep it simple and try and shoot what we can normally see with the naked eye at night. A few examples:
Equipment for Astrophotography
While it is important to have a camera that can shoot in manual mode to get good astro photos, it is also essential to consider the following when you choose your equipment:
- A camera that has good high ISO noise control decides the quality of your final image. Most modern DSLRs are capable of shooting clean images above ISO 800. Astro photos are generally shot between ISO 800 and ISO 3200. Shooting in RAW format is highly recommended.
- A “fast” ultra wide angle lens is essential to get good astro photos. Fast here refers to a lens that has a maximum aperture like F2.8 (small f number means wide lens opening). The idea is to gather as much light in as short a period as possible. With a wide lens, you can capture more of the sky along with an optimum amount of foreground. While it is possible to shoot the sky with longer lenses, you are limited in your compositions. However, if your intention is to shoot the moon, then having a very long telephoto lens is a must. Any lens that you use for astro work must be able to focus manually as auto focus will not work in low light.
- A sturdy tripod is important.
- An intervalometer (to shoot trails) is good to have.
- A flashlight is optional. You can use it for light painting.
It is not necessary to shoot with a DSLR. My favourite camera for astrophotography is the Sony RX100 Mark IV which is an advanced point and shoot. It has a fast aperture of 1.8 and can shoot clean images in RAW format at high ISOs.
Planning for Astro Photos
The most essential step for astrophotography is planning. How should you pick your location and plan your shot?
- You need a clear night which is as dark as possible. Hence you should plan your shoot far away from areas of light pollution on a night when the moon is either not visible or very dim. You can use apps or websites that provide details about the phases of the moon to pick a day appropriate for astrophotography. Plan your shoots during a new moon or the 4 days before or after it.
- To capture the Milky Way, you need to shoot between the months of March and October when you are in the Northern Hemisphere like here in India. The galactic core of the Milky Way is brightest between April to July. Although the Milky Way is indeed visible throughout the year, it is not very evident in other months. This excellent post describes everything you need know about shooting the Milky Way.
- It helps to have an interesting foreground when you shoot the Milky Way. So scout around during the day to find interesting spots where you can shoot later at night. To capture star trails, it helps to have the foreground aligned with the North Star.
In India, it is best to go to higher altitudes to get clear skies that are free from air and light pollution. Places like Ladakh and the high mountains in Uttaranchal and Himachal are great for astro work. In the plains it is nearly impossible to get clear skies in cities and towns, so the best thing to do would be to drive a little away from areas of human development.
Useful Apps and Websites:
The mother of all photography planning apps is Photo Pills (iOS and Android). It is an all-in-one tool that can help you, calculate exposures, find the Milky Way, North Star among a bunch of other things.
Shooting Astro Photos
There are different types of astro photos that you can take. In all of these types, the idea is to get the basic exposure right in the camera. Once you get the exposure correct, you can fine process the photo in a computer to extract more details and make the celestial objects stand out.
Apart from capturing the night sky, you can even try light painting to make interesting astro photos. Mixing steel wool photography with a star-studded night sky is a popular idea. In all these methods it is important to balance the exposure from ambient and artificial light. Use the settings given here as a starting point and experiment based on the situation in the field.
Milky Way Photography
To capture the Milky Way you need to release the shutter for long durations to get the maximum amount of light into the sensor. Since you shoot when it is dark, the exposure times are generally in the order of 20 to 30 seconds when the aperture is larger than f2.8 and the ISO higher than 800. The Milky Way is faint compared to the stars, so do not try to mix ambient light when shooting for the first time.
You must set the lens to manual focus and focus to infinity. Auto focus would fail in low light. If your lens does not have an infinity focus marking, find out the infinity focus point during daytime and make a note of it by placing a dot in your lens.
Here are typical camera settings that you can start with when it is a really dark night with no artificial light:
- ISO: 1600
- Shutter Speed: 30 seconds
- Aperture: F2.8
- Lens focussing: Manual and focused to infinity.
- Long Exposure NR: Turn Off
Needless to say, you should mount your camera on a tripod before you click. You can never hand-hold the photo when the exposure times are long. After you shoot, review the photo on the back of the LCD to check if the exposure is correct. It helps to use the histogram in your camera to see if the image is under exposed or over exposed. You can also check to see if the Milky Way appears correctly in the photo and if the stars are in focus. The stars and Milky Way may not look as evident as you see in the photos below. That is alright. Processing them later in a computer will bring out the colours, clarity and contrast.
Adjust the exposure and focus settings based on what you see. If the image looks over exposed, reduce the shutter speed and ISO instead of narrowing the aperture. When the shutter speed is longer than 30 seconds the celestial objects don’t appear sharp. The earth’s revolution causes them to be blurry.
Tip: Use a remote shutter release or the built in timer your camera to avoid shake induced by your finger when you hit the shutter.
Star Trail Photography
To capture the movement of stars in the sky as trails there are two methods that you can follow. In method one, you could leave the shutter released for longer than 30 minutes. In method two, you several photos that are of short durations and stitch them later using a software like StarStax. The disadvantage of using the former method is that having the shutter released for long periods of time causes the camera sensor to overheat and the battery to drain faster. The most preferred method of shooting star trails, hence, is to take individual exposures and combine them later.
You can use the same camera settings as for shooting the Milky Way to shoot the individual exposures. Use an intervalometer to take photos at predetermined intervals. Set a 2 second gap between shots and take at least 30 – 50 photos that you can stitch later. If the exposure of each photograph is 30 seconds, and you have a 2 second gap in between photos, you will need approximately 53 minutes to shoot 100 photos (32 seconds x 100 = 3200 secs which is approximately 53 min). During this time, you must take care that your camera lens does not get fogged up due the weather conditions and you don’t move the camera or get cloud cover in your frame. Both of these will ruin the final image.
To get concentric star trails around your subject of interest you must compose taking into consideration the position of the North Star because all other stars revolve around the North Star.
Capturing Just the Night Sky
It is not necessary to always include the Milky Way or do star trails when you shoot the night sky. You can take very nice landscapes photos with celestial objects in the frame. The settings here then varies based on how you wish to balance the ambient light from man-made objects and the light in the night sky. A good starting point would still be the settings given above.
Processing Astro Photos
Astro photos need extra care in the digital darkroom. My software of choice for post-processing is Adobe Lightroom and Adobe Photoshop. But there are several tools out there. Always shoot in RAW to get the maximum quality after image processing. Here is an overview of the steps involved in processing an astro photo:
- Noise reduction: Because astro photos are shot at ISO 800 and above, it is important to apply noise reduction techniques to clean up the image. It is best to turn off in-camera NR and use noise reduction algorithms in a image processing software.
- Haze removal and clarity improvements: To cut down the amount of haze in a photo (which is usually due to pollution and weather conditions), increase the clarity, contrast and run the de-haze tool (Adobe Camera RAW only). This can dramatically increase the visibility of celestial objects.
- White balance correction. Most cameras don’t get the white balance correct when shooting at night. One of the biggest advantages of shooting in RAW is that you can change the white balance later in post processing. Change the white balancing to something cooler to mimic the appearance of the night sky as we see with our naked eye.
- Sharpness: Increase the sharpness to make the stars stand out.
If you are combining images in StarStax, process the individual photos first before running them through StarStax. This is where the batch processing power of Lightroom comes in handy.
You can even go to the extent of compositing your photo to replicate something you had in mind but could not achieve in the field. Here is an example:
Astrophotography is fun and addictive. But remember that there are very limited opportunities in a year. In India, the monsoon season coincides with the months when the galactic core of the Milky Way is the brightest. There are only a handful of new moon days in any calendar year. There is generally a lot of light pollution around. So it is essential to plan your shoot before hand. Also take safety into consideration when venturing away from human development.
While it is not possible to shoot good astro photos inside Bangalore city, a short drive towards the outskirts presents excellent opportunities. For example, this photo was taken near the town of Kanakapura:
Once you master the art of taking good astro photos, you can move on to shooting time lapses of the night sky. Watch the video I made after my visit to The Goat Village to see how the movement of stars makes for a great time-lapse.