Saturday, July 24, 2010

How to Photograph the Milky Way


This summer I’ve been making quite a few wide-angle astronomical photos, especially of the Milky Way. Here are links to a collection of photos taken in June in the San Rafael Swell, and some other miscellaneous astronomical photos.

When I show these photos to people, they often ask how to make similar photos themselves. Here’s a summary of what I’ve figured out so far. For much more advice on astrophotography, I highly recommend Jerry Lodriguss’s site.

To photograph the Milky Way, you need the following:
  • A camera. I use Canon’s cheapest digital SLR, the Rebel XS (street price $500). Any other DSLR will probably work fine, except perhaps some of the earliest models which have higher noise levels. There may now be some high-end point-and-shoot cameras that will give acceptable results, but I’m not sure of this; most point-and-shoot cameras can’t take long enough exposures, and even if they could, the noise levels would be unacceptable. Film cameras don’t work well because even the fastest readily available films aren’t as sensitive to dim light as the sensor in a DSLR.
  • A wide-angle lens. I’ve invested in a Sigma 20mm f1.8 lens ($520), although the inexpensive 18-55mm zoom lens that came with my camera was good enough to get started. If money is no object, get the Canon 24mm f1.4 ($1700), along with a full-frame Canon 5D ($2500); that’s what the pros seem to use, as far as I can tell.
  • A tripod. I got a perfectly usable one at a discount store for $29.
  • A dark site. This is the most difficult part for many people. You cannot make decent photos of the Milky Way from a light-polluted city. But here in Utah, there are some very dark sites within a one-hour drive of my urban home. Depending on where you live, you may need to travel farther.
Of course, you also need a clear sky with a view of the Milky Way. From the northern hemisphere, the best views of the Milky Way are in the summer, with the brightest parts in the southern sky.

Before heading out on a dark night, practice with the settings on your camera. Put it in fully manual mode, including manual focus. Set it for a 30-second exposure at ISO 1600, with the lens at its widest aperture (perhaps f3.5 on a zoom lens). Practice turning the display on and off, and turn its brightness down. Set the camera to store images in “raw” format, rather than jpeg. Most importantly, figure out how to manually focus the lens at infinity. Some lenses are conveniently labeled for focusing, but my zoom lens isn’t, so I had to mark the infinity setting (when zoomed out to 18mm) with white tape.

With this preparation, taking the photos should be pretty easy. Turn the display off when you’re pointing the camera (so it doesn’t ruin your eyes’ dark adaptation), then turn it back on to check the settings (30 seconds, ISO 1600, widest aperture) and fire away. It’s hard to compose a photo in the dark, but you can review the composition on the LCD and try again as needed.

After downloading the photos to your computer, use the software that came with the camera to adjust the brightness, contrast, and color balance. With “raw” images you can make some pretty dramatic adjustments without losing quality.

Speaking of quality, there are three factors that limit the amount of detail in a photo of this type:
  1. Digital noise, which gets worse at higher ISO settings;
  2. Lens aberrations, which blur and dim the edges of the image, and which get worse when the lens is opened to a wide aperture (low focal ratio);
  3. The earth’s spinning motion, which turns star images into trails and blurs the Milky Way over time. (In 30 seconds the earth turns by 1/8 of a degree.)
To lessen any one of these problems, you generally need to worsen one of the others. The trick is to make sure that no one of them is much worse than the other two. By all means, experiment with different ISO settings, apertures, and exposure times. I always stop-down my Sigma lens to about f2.8 to reduce aberrations, but stopping-down may not be an option if you’re using a relatively slow zoom lens. I’m happy with ISO 1600, which is the highest setting on my camera. Most of the digital noise disappears when I reduce the photos to screen size, but in long exposures there are always some “hot pixels” which can be manually fixed in Photoshop if necessary.

Even with the most expensive equipment, photos made in this way will not be sharp enough to withstand poster-size enlargements. For example, I’m a big fan of Wally Pacholka’s photos, and I have a framed 36-inch panorama of his in my living room, but it doesn’t show much more detail at that size than in the screen version on his web site.

It’s a nice touch to include foreground scenery in your photos, but if you want more than silhouettes, you’ll need to plan carefully. A small amount of artificial light, from ambient light pollution or even a flashlight, can sometimes illuminate the scenery without ruining the Milky Way. Moonlight is another option, but anything bigger than a crescent moon will brighten the sky too much for a good Milky Way photo, and there are only a few nights each month, and a few hours each of these nights, when the crescent moon is above the horizon after dark. Even then, the moonlight won’t always be shining in the direction you want.


If you don’t want to include foreground scenery in your photos, then life becomes much easier. You can try using a tracking mount to compensate for the earth’s rotation, allowing much longer exposure times. Then you can use a smaller aperture and/or lower ISO setting to reduce problems 1 and 2 above. You can even use a film camera, which is far less expensive but requires additional skills and patience.

48 comments:

  1. Here's a similar advice article from a pro at National Geographic, which I highly recommend for a complementary perspective. Let me comment on the many respects in which Richardson's advice differs from mine.

    Most importantly, I disagree with Richardson's implication that you need a $5000 camera-lens combination to make decent Milky Way photos. My current setup cost barely over $1000, and you can get started with a $500 digital SLR and kit zoom lens. Nobody should run out and spend thousands of dollars until they've pushed the limits of what can be done with a less expensive camera.

    If you do want to spend $5000, Richardson recommends Nikon equipment rather than Canon. All I can say is that there are others out there who disagree. He may be right, however, about the uniqueness of the Nikkor 14mm lens.

    Using this super-wide-angle lens, Richardson is able to get away with a 90-second exposure time. Note, however, that his Owachomo Bridge photo is displayed at only 600 pixel resolution. An enlargement would show noticeable star trailing. If you don't have such a wide lens, you can still make wide-angle photos by stitching together multiple shot--as long as they're taken in rapid succession to get the stars to match up reasonably well between frames.

    I also disagree about the necessity of using in-camera noise reduction. I don't use it, because it doubles the time required for each photo. If necessary, I can accomplish the same thing at home by subtracting a dark frame (one dark frame taken per night, rather than one for each photo!). But for screen resolution, even that's not really necessary.

    Finally, Richardson suggests that you probably can't make a photo like this east of the Mississippi. Obviously the right conditions are much more prevalent out West, but there do exist suitable sites in the East, and there are photos to prove it, including this one.

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    1. Thanks Dan, you guidance is highly appreciated

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    2. You can put a Nikkor 14mm lens on a Canon - there is a company that makes the mount to do it

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    3. I live 1/2 mile of the mighty sippi. Still gonna try this. ;)

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    4. 1/2 mile east that is ...

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  2. I now see that Richardson's article is also posted on his personal blog, where you can click on the photo to see a larger version. Sure enough, the star trails are quite noticeable. Not that this necessarily detracts from the photo. But I think it does make the extra-sharp lens a little superfluous.

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  3. Thanks, Dan.
    Good info. I live in South Jordan. Any good
    Dark places that you know of. I was thinking Antelope Island area or the desert area west. But want to be safe as well.
    Jerry
    Jcpayne@gmail.com

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  4. Jerry,

    Not sure what kind of "safe" you're referring to. I've never been to Antelope Island at night, but I suspect it's not very dark compared to Utah's best sites. From South Jordan you shouldn't have to drive too far to find dark skies to the south. From here in Ogden it's tough to escape the glow of SLC.

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  5. Thanks, Dan. I was at Silver Lake in Big Cottonwood Canyon
    today. I may give it a try. Will let you know.

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  6. Hello Dan. My Milky Way shot is at www.coffeebuddha.com. It
    turned out ok. Looking forward to better ones. Thanks. Jerry

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  7. Jerry--very nice! That's a WIDE lens you've got, putting Cassiopeia and Aquila in the same frame! I'll bet you could pull out more detail in the Milky Way if you fiddle with the curves in your photo software.

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  8. Thank you. Got some learning to do. Take care. Jerry

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  9. Great blog and thread, Dan! I'm really dying to try out this technique. You say to use the widest aperture you can, and here (and elsewhere) I see that those apertures are usually in the f/1.8 to f/2.8 range. I shoot with a Pentax K-7 and while I love Pentax, it's hard to find a wide angle lens with that kind of aperture. I have a 15mm f/4 prime and a 12-24 f/4 zoom. Do you think shooting at f/4 will be adequate? Thanks so much!

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  10. Thanks, Rob. I think f4 should work with a lens that wide. The wider the lens, the longer an exposure you can get away with before trailing becomes noticeable. So where I would use f2.8 for 30 seconds, you could use f4 for a full minute. Good luck!

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  11. Thanks Dan! I'll try it out and see what happens. If it doesn't work, I can try some other lens options. I really hope so, this technique is so cool!

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  12. Dear Dan,

    You have a fantastic blog. I will try out your suggestions tonight. I am planning to go to Shenandoah national park and I hope I will get some real dark areas. I will let you know how it goes.

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  13. Hi Dan, another question. I am intending to try out this technique on the New Moon (July 30th), which is supposedly the darkest night of the month. I'm a little confused, however, about what time of night to try this out. Can I basically just go out any time after dark and shoot away? I understand the New Moon will be at 18:40 (or 6:40) Universal Time (is that the same thing as eastern standard time?). I've read elsewhere people doing this technique where they seemed to time it with the exact timing of the New Moon, but at that time where I live, it wouldn't even be dark out yet. So can I basically just go out any time or do I really need to pick a specific time of the night? Thanks again, I appreciate your suggestions....

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  14. Rob, unless you're photographing a solar eclipse, the exact time of new moon doesn't matter at all. Any time within a few days of new moon, the moon will be below the horizon whenever it's completely dark so there will be no moonlight to interfere with dark sky photos. More generally, if you can't see the moon, it can't affect your photo!

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  15. Great! That's what I was hoping to here. Makes planning much simpler. Thanks, as always, will report the results of my adventure!

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  16. Thanks for this post! We're headed to Moab soon, will have to try this out.

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  19. Dan,
    I also live in Ogden. It's funny that I happened across you blog, as it was a general Google search. I'm heading up past cemetary point tomorrow night to attempt this for the fist time, and this will be helpful. One question: When you say that you can use a single dark frame and subtract from it, is that just a layer blending technique in Photoshop? As in the layer blending mode being "subtract"?

    I am shooting with a 7D and a Canon 17-55mm f/2.8. My camera does fairly well with ISOs as high as 3200, above that it just gets messy. I'll experiment with an ISO above 1600 and see how it goes as well, to try and get faster shutter speeds. Thanks for the well thought out post!

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  20. I go to Antelope Wells on the border of Mexico and New Mexico where there is drug smuggling and illegal aliens walking around. it is the closest dark sky I can get to, where I used cloudydarksky.com to tell me where to go. I don't have an expensive lens I have an 18-55mm f3.5 kit and a rebel t3 I take ISO 6400 35s 18mm and get some great shots. So you don't really need those 300-1700$ lenses at all. Also, I once borrowed a friends 110$ 50mm 1.8 fixed lens and got much better pictures than I did with 18mm at 3.5 so you could purchase that very cheap lens and get amazing pictures of the sky. Use cloudydarksky.com to find a dark area close by spend 110$ on a lens and find a 400$ dslr camera on Craigslist.org and you are in business. It doesn't take that much money to get good pictures. If you want amazing pictures, then sure you need 5000$

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  21. Rocco: Hope you got some good photos! Yes, the "subtract" layer blending mode is what I had in mind--though I've done this only rarely myself and I know there's better software for it than Photoshop.

    Anonymous: ISO 6400 certainly buys you some flexibility with lenses and exposure times. Since my camera doesn't go above 1600, I can't comment first-hand on whether the trade-off is worth it. Tried connecting to cloudydarksky.com and I keep getting an error saying it's not there.

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  22. Thanks for the tips on shooting the Milky Way. I live in an extremely light polluted area in Florida, but will be visiting central Texas for Christmas and hope to find some really dark skys there.

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  23. Nice article. You have inspired me to try it! I have a Russian Zenitar 16mm fish-eye that captures about 90 degrees horizontally on my 1.5 crop Nikon DSLR. I figure that would be slighly wider than a 14mm regular lens. With a max aperture of 2.8 it seems that I would have a chance of a decent milky-way if I can find a place dark enough.

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  24. Thanks for those in-depth tips. I'm really eager to try this out on my 600D.
    Biggest issue I have is finding a place dark enough. I live in London, which is obviously one of the biggest cities in the world. Worse yet, it's surrounded by smaller towns and farmland, so finding a true dark spot would be couple hours drive away probably.

    Just one question. I don't have a motorised tripod nor the DIY skills to make one myself. Is there anyway to avoid the "star smear" effect on a stationary tripod? I've tried shooting at 30 second exposure before and I got very tiny lines. Actually quite surprising how fast the earth spins!

    Cheers.

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  25. Jens

    If you have a canon take a l look at this
    is an addon firmware that open op a new world

    http://magiclantern.wikia.com/wiki/Magic_Lantern_Firmware_Wiki

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  26. Hi Dan,

    I've just started trying to get some photos of the milky and I am just after some advice please. I have a Nikon D3100 with the stock 18-55vr Lens and I have tried to get some 30 second exposure shots of the milky way here in Oz. My problem is that I have found that with an exposure of 2 minutes I can get some really nice clear shot (colour wise) but of course with the 2 min exposure I run into problems with the blurring of the stars.

    Basically my question is what is the easiest way of getting a nice clear shot of the milky way without having a really long exposure and getting blurring. Is it just a question getting a better lens that can go to a lower F stop (I have used 3.5) or would i need an equatorial platform for a longer exposure but I am then assuming I can't have anything in the foreground for that?

    Thanks in advance.

    Matt

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  27. Matt,

    I'm not sure what you mean by "nice clear shot (colour wise)". Colour of what, and what was the light source? With a fixed tripod, to keep the sky from blurring noticeably due to earth's rotation, with your camera and lens, you need to keep the exposure times at about 45 seconds or less.

    Dan

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    1. Sorry Dan I meant that with the 2 min exposure the colour's of the milky way that i got were obviously far more prominent and exactly what I wanted but I had blurring of the surrounding stars, when I tried the 30 second exposure I am failing to get that brightness but eliminating the blurring. I suppose I just would like to know how to get stand out pictures within the shorter exposures. I have been using ISO's ranging from 400-800 as I didnt want to go any higher as I had been told this would create excess noise in the picture.

      Thanks

      Matt

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    2. Well, the first thing I'd try if I were you is turning the ISO setting up to 1600 (or more if possible). This does increase the amount of digital noise, but as described in this article, there are other factors that limit your resolution so digital noise probably won't be your main concern.

      Are you shooting in RAW format? If not, be sure to do that so you can make the full range of brightness and contrast and color adjustments on your computer.

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  28. Dan- Great shots. I am a newbie and getting ready to make the purchase. I've been debating btw telescope vs. wide angle dslr (scenic shots of milky way). Due to lower cost (probably) and portability, I think getting a fixed tripod, canon dslr T3i body and fixed 20 sigma that you have would be a nice start. What kind of tripod do you use and do you use a remote switch or right angle finder? Did you have your dslr modified? Please respond by emailing briantodd41370@yahoo.com

    Thanks~
    Brian

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  29. This comment has been removed by the author.

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  30. I've had two goes at this so far. One in the UK:-
    http://www.flickr.com/photos/thedavewalker/4975124804/

    And again in Crete:-
    http://www.flickr.com/photos/thedavewalker/6244214420/

    Both courtesy of the great value for money Samyang 8mm fish-eye lens

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  31. I intend to try again with longer exposures on an equatorial mount, but, I think it's important to recognise that whatever you do, there's always someone doing it better than you. If it's any consolation, someone else will be thinking you're doing it better than them! So, don't give up, just keep at it, and find your own 'sweet spot'.

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  32. Great stuff Dan! Another trick to get longer exposures and eliminate star trails is to take several very high ISO shots and "stack" them afterwards using software. One very good (free) one is DeepSkyStacker. I usually take 20-30 second shots (wide angle) and a few "dark" shots (put on the lens cap) then put them through the software. It auto corrects star trailing and reduces noise (using the dark frames) at the same time! I have also used this process with a 50 or 100mm lens pointed at a galaxy eg. Andromeda, but using 5 second exposures and slightly lower ISO to minimise trailing and noise at the enhanced magnification.

    Now just hoping for a clear night in (naturally) cloudy Ireland! Happy shooting! Rob (viewsofireland.com)

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    1. Hi Rob,
      This is really good. Just a quick tip on top of this, do not use the lens cap for your dark frames, simply take a black baseball cap (or piece of black cardboard) with you and put it infront of the lens. I find attaching and removing the lens cap quite often affects the focus.

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  33. Hi Rob

    Do you happen to have any shots of galaxies/nebulae that you've shot using that technique we can see? I'm interested as if that works I won't need to forking out best part of £1000 for a decent scope! :p

    I'm hoping to head out to Dartmoor in Devon the next time it promises a clear night for a bit of milky way action.

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  34. I'll get this right one day.... previous message was meant to say my name is Sam, btw... forgot to add it before!

    Thanks, Rob!

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  35. You can look at light pollution maps like this one to find a suitably dark location:
    http://cleardarksky.com/lp/SpnsFkUTlp.html?Mn=photoshop

    The white splotch you see is Salt Lake, the lower red one is Provo, the crosshair is near my location, Spanish Fork. Probably want to aim for the blue, gray or black zones, can get by with a green zone. You can also download a Google Earth overlay at that link.

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  36. good ideas everyone, gonna try this tonight, im using a Canon T3i with tripod and Rokinon 8mm Fisheye, see how that holds up.

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  37. I just moved to Colorado and I'm going to take some pictures tonight; back in PA I used to get some decent once, but the light pollution on the East Coast is significantly greater than out here. It made me so happy to see you have the same camera & lens I do, leaves me feeling like I might actually be able to figure it out tonight. So, thank you for your tips, I'm really excited about tonight, now. :)

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  38. Thanks for the advice and links...Shot the milky way at Death Valley and am planning to visit utah parks this fall...Can you still get good shots in the fall? I know summer is best

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  39. This questions puzzled me for years. Being in it, we can't actually "see" the Milky Way, only observe what it looks like. How could we actually observe the shape of it? Say we sent a probe straight up, 90 degrees to the Galactic plane, how long would it take for it to reach an altitude where it could actually photograph the Milky Way and its shape?

    phlebotomy training colorado

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    1. You're right to be puzzled. The Milky Way is so huge, there's no foreseeable way to send a probe far enough to get a view of it that's noticeably different from our view from earth. So astronomers have to figure out its shape from inside, which basically requires estimating distances to various features that we see. It ain't easy, but lots of smart people have been working hard on the task for many decades now, so the "picture" is becoming reasonably clear. In another decade, we'll have data from the Gaia probe which will measure accurate distances to huge numbers of stars across much of the galaxy.

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