Gazing at the Milky Way, Homing in on Infinity

Welcome

You have reached my blog about astrophotography. It is a blog post I frequently update allowing it to reflect the knowledge I have achieved on the area. My fascination of the night sky has been there ever since I was a child looking up at the endlessness, feeling incredibly tiny and overwhelmed. This feeling and fascination has stayed with me and frequently drives me out at night, trying to capture this magnificent display and attempting to perfect my skills in one of the most frustrating forms of photography there is. Astrophotography is photography on the edge of the possible, it is not an area that I will ever master, I don’t think I ever will perfect my skills, and I find myself continually learning every time I go out or talk with other photographers.

The reason why Astrophotography is especially frustrating is that there is no one size fits all solution. The cloud cover, the vapor in the air, your position on our planet, the time of year, and the earth rotation, moon phase, surrounding light pollution, an endless row of factors that forces you to adopt along with your type of motive and types of astrophotography you pursue.

This blog will with time deal with Wide Field Astrophotography, Deep Space, Solar system and Time-Lapse Astrophotography. But it takes it starting point in Wide Field Astrophotography which is the most assessable form of astrophotography. The blog is planned to gradually work its way into Deep space homing in on objects beyond our own solar system. Taking photos of distant galaxies and nebulas. This kind of photography is much more demanding, technically and also in terms of equipment, moreover does it require a deeper knowledge of stacking photos in the post process.


Where and when to meet up at the Milky Way

The Earth’s relative position to the Sun determines when we can see the whole Milky Way. The Milky Way is visible all year around, but parts of the year is the Milky Way’s core blocked by the sun. This means that the best time for viewing is from late May to early August.

The Milky Way moves in the sky following Earth’s rotation as the stars move, this means you will have different compositions at different times of the night.  You can get the band of the Milky Way in vertical, diagonal or horizontal orientation. Knowing the direction where it is possible to find the core of the Milky Way is mandatory. If you are located in the Northern Hemisphere: look towards the southern skies to see the galactic core. The core will start to be visible in the spring if you head due southeast, in the summer time you will have to head south and in the fall southwest. If you are located in the Southern Hemisphere: Then you will also find the galactic core in the southern skies. It will be visible southwest in the spring, southeast in the winter and fall.

Another way to find the center of our galaxy and the brightest part of the Milky Way is to look for the constellation Sagittarius.

Equipment you cannot live without

The entry point for Wide Field Astrophotography is as said fairly accessible. All you need is

  • A digital camera. Ideally you want a full framed sensor camera like Sony Alpha A99V. One of the advantages of using a Full Frame camera is that, typically, noise performance is much better than in APS-C cameras, allowing you to use higher ISO values. This is due to the larger sensor of a Full Frame camera which collects more light per pixel.
  • A wide lens. Not all lenses are born equal, a fast wide prime like the Samyang 14mm f/2.8 is preferred. Aim for the shortest focal length you can 14mm to 24mm. Short focal lengths is essential to capture as much sky as you can and get the longest exposure without star streaks. A fast prime are also important, we want aperture in the f/1.4 to f/2.8 or faster.
  • A sturdy tripod. What is important here is the stability, buy a heavy and big tripod. There is in my mind little reason to buy an expensive carbon tripod, as we are not going to carry it around taking photos in several locations. Astrophotography is usually at the same location all night J

Stepping up involves additional accessories like interval meters the JYC wireless that features a LCD screen, remote controls, equatorial mounts like the IOPTRON sky tracker which follow rotation of the night sky.

Having a LED forehead headlight is also very convenient; mine has the additional feature that it can give red light. This is better while it doesn’t impact your night vision nearly as much.

 

Setting up for that shoot of awesomeness and darkness

Exposure time. To avoid streaks, we keep the “500 rule” in mind. It is a rough tool for figuring out how to avoid noticeable blur, or unwanted star trails. Take the number 500 (multiplied by the crop factor if you are not on full frame) and divide it by the focal length of your lens to get maximum time in seconds before trails will appear. The number 500 is only a rough guide, and new optimized sensors affect it, so experiment with it until you find your camera’s number. The correct number is typically somewhere between 450 and 600.

ISO. Open the aperture as wide as possible (If the stars are the only consideration in your subject). We usually work with ISO within the range of 400-3200. Using a higher ISO setting will introduce too much grain into the image. From there it is about fine-tuning based on what looks good, the amount of ambient city light affecting the shoot.

Colour Balance. Colour balance can be tricky; while it really depends on the motive, sounding light, vapour in the air. And not least, preferences, what colours do you find natural and pleasing. But no needs to worry as long as you shoot in RAW, all is fine, colours can be fine-tuned in the post processing. I generally look for white balances in the range 3600-4200 kelvin.

Image stabilization, or vibration reduction, O.I.S., Optical Steady Shot, SR, VC, VR, MEGA O.I.S., and other equally catchy monikers, are technologies that enable us to take pictures under less desirable lighting conditions and still get sharp still images. Common for them all, it is not a thing we desire when our camera is rock steady. Using them with a tripod, can, depending on technology result in anything from blurry photo’s to broken equipment.

Aperture, if you only want to shoot the star collections then infinity is your focus, then DOF has no relevance, it is about gathering the most light possible. This means you would want to shoot at the widest possible your lens can do.

Rule of thumb settings

  • f/1.4    ISO 1600    30sec
  • f/2.0    ISO 3200    30sec
  • f/2.8    ISO 6400    30sec
  • f/3.5    ISO 10000    30sec
  • f/4.0    ISO 12800    30sec

     

If you have objects in your picture, with the Milky Way as a background… then things start to become complicated. We need everything sharp from the object to the back of the scene. Since focusing your camera at the hyper focal distance ensures maximum sharpness from half this distance all the way to infinity. You only need to calculate the hyper focal distance for the focal length and aperture you want to use. This is by no means easy, and involves quite a bit of math. My suggestion is to use a depth of field (DoF) calculator to automatically get the hyper focal distance.

Figure 1 Photo of Sletterhage Lighthouse shot by Claus Møller

 

Stability and focus

Stability is essential; astrophotography requires as little ambient light as possible. To capture the Milky Way in detail you will be heading for long exposures. Camera movement is undesirable, so a sturdy tripod is needed. Triggering the shoot remotely is also recommendable, while the slightest vibration from using the shutter release will affect the quality of your picture. If you do not have a remote, then use the build-in self-timer.

Setting infinity focus at night is especially difficult, it will have to be done manually as autofocus doesn’t work in low light, Setting your lens on the infinity ∞|L sign, still leaves you out of focus, the reason for this is often that the lens isn’t calibrated, or changes in temperature. My experience points to two solutions for how to figure out the correct “infinite” focus.

Setting infinity focus on a Prime is also much easier than setting it on zoom lenses. The slightest shift in focal length when changing your manual focus will ruin your work.

Ad-hoc solution: On my Sony A99, the translucent capabilities really help when setting infinity focus. Find a bright star on the sky, and then apply Focus magnification at 11.7x (Sony Alpha A99V Page 103). This will aid you setting your manual focus on the star. Once you have set your focus, secure your lens with a piece of good-quality insulating tape or duct tape and point towards the part of the sky where you want to take your photo.

Mark-up solution: Pre-set Your Focus Point during the Day, it is much easier to focus during the day than at night, adjust your lens to focus at infinity, or at a faraway horizon. I always like to use my camera’s Live View Mode, zoomed in, and focus on the furthest horizon in my composition. This will ensure that you’ve focused at infinity. Next manually make the final adjustments if / as required using the focus ring. Using a permanent marker, mark both the focus ring, and the barrel of the lens (non-rotating part of lens) using a silver Sharpie, allowing me to see the mark at night without using a headlamp or light.

        

We seek out the darkness places

Light pollution is excessive, misdirected, or obtrusive artificial light. It washes out starlight in the night sky. Not many generations ago people was able to walk outside at night even in a city and see the Milky Way galaxy arch across the night sky. Being able to see thousands of stars was part of everyday life. Now we have to get away from city lights to increase our chances of getting that crisp belt of stars decorating a black carpet.

One of the good things about stars is they always have the same brightness, so any adjustments you need to make will have to-do with either light pollution or moonlight. Do find places with the lowest amount of light pollution possible. This might sound simple, but depending on where you live, it can be very challenging to find a location with limited light pollution. These are some resources that can help you find dark sky locations:

Dark Finder is my favourite. Here in Denmark it is close to impossible to find “real” darkness, last time we ended up shooting at a green light zone, at “Poskær Stenhus” .

        

 

Examples by Gary Plummer

Web Album

Video of the Northern light and the Milky Way


 


To be continued

3 thoughts on “Gazing at the Milky Way, Homing in on Infinity”

  1. Great job Jorgen. Concise and completely relevant. I get many people asking for advice when starting out and this is the first place I shall point them to. Looking forward to your next instalment; Gary 🙂

  2. January 3-4, 2015 Quadrantids

    April 22-23, 2015 Lyrids

    May 5-6, 2015 Eta Aquarids

    July 28-29, 2015 Delta Aquarids

    August 12-13, 2015 Perseids

    October 8, 2015 Draconids

    October 21-22, 2015 Orionids

    November 4-5, 2015 South Taurids

    November 12-13, 2015 North Taurids

    November 17-18, 2015 Leonids

    December 13-14, 2015 Geminids

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