I assume you already read part one of this article which describes a bit about what the Milky Way is and what times and seasons are best for photographing the cloud-like expanse of innumerable stars. In this installment we describe the equipment and settings you will need.
f/2.8, ISO 3200, 30 seconds, post processed
To get a passable or better image of the rather dim Milky Way you need:
- A high performing low light camera (more on that in a moment)
- A large aperture (f/2.8)
- A wide angle lens. Ultra wide even.
- A cool/cold night
- As little city glow and moonlight* as possible – see below for an image taken in twilight
- A solid tripod
- To know where and when to look!
To get a recognizable Milky Way in a single frame, you’ll want to use somewhere between 1000 and 3200 ISO at f/2.8 or wider setting. That’s very high, and a wider aperture than many people have paid for. You’ll also want to expose as long as you can before stars are streaking. We recommend starting at 30 seconds, and reducing your exposure time if the streaking is objectionable. Below is an image taken when twilight was beginning to wash out the sky and this may be typical of attempting to capture the Milky Way in a less than ideally dark scenario. The foreground is lit with a powerful spotlight.
38 seconds, f/2.8, 16mm, ISO 3200
In the large size minor streaking of stars is evident.
Some image degradation is to expected. For example vignetting and coma are both more obvious at lower f/stops. Coma is a comma or “bird-wing” like appearance of stars near the corners of the image. Both coma and vignetting can be overcome by stopping down the shot – but resist the temptation because stopping down means losing some or perhaps all of the wispy milky goodness that you are trying to capture. Exposing longer will only help if you have some special apparatus (see Tracked Capture below). Are you wondering why exposing longer does not solve the problem? We have tackled the issue in two different styles: a cheerful allegorical example, and a recent math savvy explication.
What will an image look like captured with 3200 ISO? It may look like the image on the left below which is “straight out of the camera” – but perhaps not for you as this image was taken in a VERY dark sky area in Nevada. On the right is the same Milky Way with some simple processing we will describe in the next installment.
What is a “High Performing” Camera?
I qualified my statement earlier by indicating a “high performing” camera is needed for a standard capture like those I’ve shown above. Since it would be impossible to keep an up-to-date list of the current “high performing cameras,” let me instead point out a few characteristics common to all high performers:
- Recent generation (2 or 3 years since introduction) is preferable because technology has steadily improved.
- Large pixels (to collect more light). A common measure of the pixel size is in microns. Generally this puts full frame cameras ahead of cropped cameras.
- High “ISO at Unity Gain” – this is a measurement of the efficiency of the sensor. There are two good sources for this information: the DxO Sensor Scores and ClarkVision’s (older) tables.
Don’t be fooled by the “highest ISO” setting advertised. That number is completely meaningless.
As of November 26, 2012, the highest performers are listed by manufacturer and in order of performance. E.g. the D3s is better than the D800 – though the difference is small. Indeed, the D800 excels in some categories over the D3s. Cropped cameras are shown in italics - note how few there are!
Nikon: D3s, D600, D800E, D4, D800, D700, D3, D3X, D5100, D7000, D3200
Canon: 1Dx, 5D Mark III, 5D II, 1DS III, 1DS II, 5D, 1D III, 1D II
Sony: Alpha 900, Alpha 850, Alpha 580, NEX-F3, NEX-C3, NEX-5N, NEX-7
Phase One: P40 Plus, P65 Plus
Pentax: 645D, K-5 II, K01
FujiFilm: FinePix X100
The list above shows all cameras having a DxO Sports (low light) score of 1000 or higher. Cameras like the Nikon D90, Canon 1D II N, Phase One IQ 180, Canon 1Ds, Nikon D3100 and Leica M9 fall just below this threshold and may also be suitable. The first five Nikon models outperform the Canon 1Dx, 5D III and 5D II. The Fujifilm just barely cracks the list in 35th and last place.
If you want the camera to cost less than $2,500 USD your current top choices are: Nikon D600, Canon 5D II, Sony Alpha 850, the Canon 5D, or the Pentax K-5 II.
A “stacked” capture is what you may need to resort to if your camera performance is not so spiffy. The approach applies astrophotography techniques to create a lower-noise version of an image. The technique requires MANY shots of the same view. However using this approach you will want to avoid having anything but sky in your photo. Terrestrial elements will make stacking the image tricky.
The image at the left is a stacked capture to illustrate the point, however it was done with a high performing camera and only 5 images. A lower performing camera will require as many as 20 or so captures to combat the noise. The method is described in my a “Astrophotography 101” Webinar and details are walked through in Astrophotography 301. On the other hand, this image was captured in a location where the Milky Way was quite faint – alongside 7 million people in the San Francisco Bay Area so there is hope even where the Milky Way can only faintly be seen.
Details about the stacking method appeared in an earlier column as well as in an an earlier webinar.
The last way to get a great shot of the Milky Way is to track the sky with an apparatus called an Equatorial Mount. By tracking the sky at the rate of the earth’s rotation you can lengthen a 20 second capture to perhaps a 60 second one. You can also use several such captures to create a stunning “Stacked Capture”. Again, however, shots which include the land are a bit harder to pull off unless you resort to layering. What do you need to do a tracked capture? We cover that in detail in the Astrophotography 101 Webinar, but in short, you’ll want an Equatorial Mount of some sort – not an Altitude-Azimuth (aka Alt-Az) mount! A device that looks intriguing and not terribly expensive is the Polarie.
Once you get that image (or those images), you will no doubt want to tease the most pleasing photo you can out of your data. That is a topic we’ll cover in the next installment: Processing your Milky Way images.