Milky-Way Shoot and Postprocess Manual

Astronomy Society of Hyderabad in association with International Dark Sky Week.

How to Shoot Milky Way Galactic Center:

Astrophotography has become easier with development in Dslr technology. Astrophotography in its simplest form is increasing in accessibility, especially with today’s affordable, large sensor, high signal-to-noise ratio digital cameras. In my opinion, there are few photographs that have as much existential impact as a nighttime landscape against the Milky Way. This self sufficient manual will show you how to make an amazing photo of the Milky Way Galaxy with a minimum of effort and a minimum of equipment.

  • EQUIPMENT AND PREPARATION.

    >Digital camera with manual control or DSLR.

     >Wide angle lens or Kit lens.

     >A Sturdy Tripod.

     > Remote Shutter release cable/ Ir remote.

     >A flashlight

     >Stellarium App for phones and Pc for Real time Sky Data.

     >Dark Spot with less or least light pollution. Avoid Moon Luminescence also.

     > A Smart phone Sky Maps app.

DSLR:  

     A common misconception is that only a high end Dslr can be used for Astonishing Astrophotography. A basic Dslr also pretty much does the same job. So what is the difference?

Well using a basic Dslr you can achieve great pics as well but you’ll have to put some work in postprocessing. Not that the pics from a high end Dslr don’t need postprocessing. All Raw images need postprocessing to get out great results.

LENS:

Shooting the Milky way Galactic center need Wide angle lens. Similar to landscape photography

Astrophotography also needs wide angle lens so as to have a Wide angle view of your foreground as well as the Night Sky.

I suggest Wide angle lens anywhere below 24mm. Since your Kit lens are capable of using a Focal length of 18mm they can be used as well. For best results your lens must be fast, by fast I mean lower fstop number. If your kit lens are capable of f3.5 it is good enough. However a lens with f2.8 would deliver way better results.There are many wide angle lens available in the market today, 14mm, 16mm, 10 mm, 12 mm. The lower the focal length the wider view you’ll cover.

TRIPOD:

A sturdy Tripod is as important as your Dslr is for Astrophotography. Since Astrophotography involves long exposure shots you need your Dslr to be stable.

REMOTES:

A remote is something which is important to have to avoid any shake in the image that might be triggered by you while clicking the shutter manually.

  METHODS OF SHOOTING MILKY WAY:

Introduction:

The Milky Way Galactic Center needs a lot of planning to spot and click. Planning plays an important role here. The following conditions have to be considered before you head out to shoot the Milky Way Galactic Center:

  • Time of the Year: Since we are located in the Northern Hemisphere the Milky Way Galactic Center is visible to us from Feb Last week to August. The rise and set time of the milky way changes daily. To track the movement of the Galactic center and its location at a particular place and time I suggest using the Stellarium Application for Pc or phone.
  • Dark Sky conditions with No Moon: A dark location is a must. The Milky Way isn’t visible to our naked eyes coz of the ambient light. Going to places far off from the city to avoid light is the best way to shoot and spot the milky way. Any sort of light may ruin the visibility. Even the moon phase should be considered as Moon itself can act as a source of scattered light. Clouds can play a spoilsport as well in here.You can use sites like darksitefinder.com to check and plan your location of shoot.

      

      Now Moving on to the shooting part.There are two ways in which the Milky way can be shot:

 1.Normal Long Exposure Method.

 2.Multiple Shots using Darks, Lights and Bias Frames stacked together in Photoshop/Dss.

The easier of the above is the first method which we’ll be discussing in here.

Normal Long Exposure Method:

Now that you have all your equipment, are in a beautiful outdoor location with dark skies and have located the Milky Way with your smartphone app, you are ready to make a photograph. There are a number of things that you’ll need to do to make a successful exposure of the Milky Way. Here’s a checklist of what we will cover.

  • Setup your Camera
  • Focusing in the Dark
  • Choosing your Exposure
  • Exposure Adjustment

Camera Setup:

  • Shoot in RAW

RAW image files contain more data than JPEG files and thus allow for greater flexibility in post-processing adjustments.

  • Zoom out to the widest field of view your lens supports (24mm or wider)

The wider field of view will reduce streaking of the stars due to Earth’s rotation and will allow us to capture as much of the Milky Way as possible.

  • Manual focus

Use manual focus (M or MF) mode on your lens and set it to the infinity mark if possible. We will focus more precisely later.

  • Manual exposure

Set your exposure mode to Manual (M)

  • Enable long exposure noise reduction if available.

This will reduce grain on your photos by taking a second photograph without opening the shutter to record and subtract noise data from your image. Note that this will usually add additional wait time to each exposure before you will be able to use your camera again for the next exposure. If your camera takes particularly low noise images, such as a Canon 6D, you probably don’t need to enable this feature.

  • Enable the histogram in the image review.

This will allow us to see a graphic display of our exposure and adjust accordingly.

  • Use automatic white balance.

Many things like light pollution or moonlight can change the white balance of the image so just set it to auto. Since we’re shooting in RAW, we can make adjustments to the white balance later.

Focussing in the Dark:

Manual focus with Live View

This is by far the most accurate method if your camera supports it. Enable live view on your camera and use the focus checking or the digital zoom function on a bright star to make the star appear like a pinpoint. I recommend centering the star in the frame before focusing on it to have the most even focus field. Note that you may need to change the Live View settings on your camera to “exposure simulation” or “manual,”  in order to be able to see stars on the LCD. If you cannot see stars in the LCD, try focusing on a flashlight at a distance like in the method below.

Auto focus or manual focus on a flashlight that is placed far away (greater than 100 feet or so)

This can be an easy way to get your camera to focus at close to infinity in the dark but can be difficult if you don’t have a helping hand to hold the flashlight for you. It’s often best to place a flashlight next to an object in your frame that is at a distance of 100 feet or greater, the farther the better but after about 150 feet or so, it makes less and less difference. Plus, walking back and forth 300 feet just to focus your camera can be a drag. As soon as you get focus confirmation on the lit object, switch the lens back to manual focus (MF) mode to lock the focus at infinity, being careful not to twist the focus ring and mess up your focusing work. A flashlight can also be helpful if you wish to instead focus on a foreground object rather than infinity.

Regardless of the method of focus, make a test shot of the stars with the exposure settings above to check your focus. Zoom the LCD all the way into the image review to make sure that the stars look like pinpoints, if they are out of focus circular blobs, re-focus and check again. Always zoom the LCD into the preview review to check the focus, don’t take the initial thumbnail at face value. Once your shots are in focus, a piece of electrical tape or gaffer’s tape between the focus ring and the lens body can help prevent you from bumping the focus.

Choosing your Exposure:

The exposure time varies on various factors such as lens aperture, Focal length, Dslr sensor size and type.

For Full Frame Dslrs the exposure can be set for more than 30 seconds. Upto a minute or so. For Aps-C cropped sensors it mustn’t exceed 20 seconds exposure. Any exposure more than 20 seconds would result in star trails.

EXPOSURE TIME:

FOR APSC (Cropped Sensors): 20 seconds max at 18 Mm focal length. For higher the focal length the exposure time must be lesser.

FOR FULL FRAME:  Supports Bulb can shoot easily about 1-2 mins without trails.

The Lens used also determines the Exposure time. If you have anything like 14mm or 16 mm you can expose for about 45 seconds in Cropped sensor dslr without trailing.

ISO Range:

Night sky shots often require shooting above the comfort zone of the Dslr Iso range.This means you won’t be using your regular Iso settings.

Now to make this easier, Since all cameras have different Iso performances I recommend shooting different Iso levels and comparing the results.We’ll discuss this below:

Settings:

ISO 800-6400 :

            18mm focal length, 20 seconds exposure, lowest Fstop supported by the lens.F2.8 or f3.5

             24 mm focal length, 15 seconds exposure, lowest fstop

             16mm focal length, 35-40 seconds exposure, lowest fstop

             14mm focal length, 40-45 seconds exposure, lowest fstop.

Try similarly with all Iso range you have for example 3200,6400 and look for a sweet spot and use the same for shooting the milky way.Please note higher Iso range will automatically cause an increase in noise.

POSTPROCESSING:

If your image was exposed correctly, you should need only a little bit of post processing. RAW images are typically pretty flat and require some post processing to make the photograph as high quality as possible. I personally use Adobe Lightroom to process my photographs. The RAW editor that came with your camera is probably just fine. The thing to keep in mind here is that less is more. If you push the exposure of your photograph too much in post processing, you will often increase noise levels and reduce the quality of your photograph. For this reason, make your best effort to properly expose your photographs in the camera. There isn’t one right way to  process your photograph and my methods might not be best for your particular shot but in general, I focus on just three things:

  • White Balance
  • Exposure (Brightness)
  • Contrast (Curves)

White Balance

Apparently, the color temperature of the Milky Way is about 4840K . I find that 4840K is a little too yellow/orange in color, usually because there’s alway some influence from light pollution, no matter where you are in the world. A lot of astrophotographers swear by shooting in tungsten white balance (3200K) which will keep the stars looking blue. That said, I use about 3900K  most of the time for my white balance setting but this may just be a personal preference. I don’t typically pre-set white balance on my camera when taking the shot. 90% of the time, I usually just leave it in auto white balance (AWB) unless I’m shooting a timelapse sequence where I’ll set it to roughly to 3900K.

  • When shooting in RAW, we can adjust white balance in post processing so the camera settings doesn’t matter that much. Try 3900K and adjust from there. Other factors like the moon and the sun can affect your white balance. Even if both the moon and sun are set below the horizon, they will continue to turn the sky a blue tint even an hour or two after they set, forcing the white balance to a higher temperature Kelvin. Adjust until you have a nice neutral picture.

Exposure

(Brightness) Hopefully the exposure will require the least adjustment. (If you made a good exposure in the camera.) Here I will add about +0.5 Exposure Value (EV), which makes the photograph 50% brighter. Try to avoid adjusting more than +/-1.0 EV unless noise levels allow for it. You will discover that adjustments larger than +/-1.0 EV will  increase noise levels too. The amount of post exposure adjustment necessary will depend on your exposure in the camera.

Contrast

(Curves) Contrast is the final essential post processing adjustment to use. I tend to increase contrast as much as possible without blowing out highlight or shadow details. Curves adjustment allows for a more precise contrast adjustment of specific lightness values and is my choice for making detailed adjustments. With curves to can make just the darks darker and just the brights brighter. Lightroom also allows you to adjust only designated portions of an image using the graduated filter or adjustment brush tools.

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