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Cheaper Astrophotography for Beginners, Part 2

By: polymorph , 7:21 PM GMT on January 04, 2013

In Part 1 of this guide I laid out my case for beginning with wide-field astrophotography using only a dSLR you already own, or an interchangeable lens camera you can buy for ~ $500 like the NEX-5N. Most of what follows will generally be true for any dSLR or mirrorless camera, but I'll make an effort to note what is NEX-specific. I also said that you need a sturdy tripod. Because you're deliberately including elements of the landscape in your composition, you can't use a tracking mount with this method or you will blur whatever trees, buildings, etc. that are static on earth.

Here in Part 2 I will give you advice on technique and other tips for your first shoot. Please familiarize yourself with basic operation of all your equipment during the daytime before heading out in the dark.

I might write another blog dedicated to choosing the best site and how to think about framing shots. To begin, keep it very simple and shoot somewhere free of obstacles that might trip you up, while you focus on learning to use the camera at night. See what you can capture of the sky from your backyard (or apartment balcony) wherever you live. Leave pets or young children inside so they can't trip over your tripod legs, and warn anyone else who comes out to visit where they are. I have a tilting headlamp with a red LED that I use when there's not enough moon light. It keeps my hands free and preserves my night vision. Of course once I'm all set up I usually turn it off unless I'm light painting.

You can shoot almost any night of the year and see something interesting, but you probably don't want to start out in a thunderstorm for many reasons. I had to wait about five months before I had my first good opportunity to shoot lightning at night, but getting the right exposure for that is a special challenge (requiring some luck) that you can tackle later.

Notice the above photos I used for illustrations aren't particularly interesting because of the beautiful mountains they show. Could they be your back yard? Look at all that light pollution on the clouds in the first photo! You probably won't get as many stars as I get in an urban area, but sometimes just a few bright ones in the right place are more than enough.

If it is very cold out, you should pre-cool your camera in a garage or other safe place before taking it outside and again before bringing it back in to avoid excess condensation. I live in a desert where the air is dry (making the skies much clearer), but I still take this precaution. I don't want the lenses fogged while I'm taking a photo and don't like to touch them with anything to clean them more than necessary. Gradual temperature changes are probably best for the camera overall. So far mine have taken both extreme hot and cold without problems. While composing this, I brought one in from -2F and the metal was painfully cold to touch. The battery life goes way down at those temperatures, but returns when it warms up again and there doesn't seem to be much loss of overall capacity so far.

I definitely avoid getting any liquid water (or snow) on the camera as much as possible, and know it can ruin one quickly.

The exact exposure settings you use will depend on the phase of the moon as well as other ambient light sources. You won't get good results shooting stars directly underneath any kind of overhead artificial lights (and it may be that your back yard isn't a great spot for that reason, but you won't know until you try). On completely dark nights with no moon, put the camera into M (Manual) mode and set the aperture wide open (for the NEX emount lenses, f/2.8 on the 16mm or f/3.5 on the 18-55). Crank the ISO up to 3200. Choose an exposure length of 20 seconds to start and adjust up or down from there as your situation dictates. If you're shooting with the 18-55 kit lens on the NEX, start out at the shortest 18mm focal length. There's a relationship between the focal length and maximum exposure that you can push before star trails will become obvious but with the 18mm focal length you won't have a problem at 25 seconds and can push the 16mm up to 30 seconds.

Shooting on bright moon nights will require shorter exposures, or stopped down aperture, or lower ISO, or a combination of all. If there are clouds intermittently obscuring the moon, things get tougher. I have less luck on the brightest moon nights. I may get some decent still shots, but a bright moon causes lens flares and banding artifacts in the sky that mar the time lapse movies I'm making. If the clouds are intermittently affecting the ambient light, I set Aperture or Shutter priority mode instead of Manual, and play with ISO until I'm getting something pleasing in the LCD display.

I can't give you specifics for shooting in moonlight because it really varies depending on the phase of the moon and clouds. Once you have experience in how to change aperture, speed and ISO you can play with them until you get results you like in the LCD display. For the brightest moonlit nights, I prefer long exposures with lower ISO (400 being doable on a full moon if you care more about the landscape exposure than the stars).

NEX users should disable SteadyShot in the settings before shooting on a tripod. It will ruin long exposure photos. If you use it regularly you'll get used to turning it back on in the daylight when you're shooting handheld, and off again at night. Note that the 16mm lens doesn't have SteadyShot (OSS), so that setting isn't even accessible while that lens is on the camera. You can get burned by this with it wrong either way, so make a habit of reviewing it after every lens change.

I also turn off long exposure noise reduction when I'm making time lapses. You can look at the effects it has vs the time it takes. If you make a 20 second exposure it will take 40 seconds with noise reduction turned on. For the second 20 seconds nothing is being photographed. During a meteor shower you can pretty well guess which time period Murphy's Law says you'll see the best meteors.

Do you want to shoot meteors? Get an intervalometer like the one I mentioned in Part 1, and you can capture 56-58 seconds of starlight every minute, making it virtually impossible you'll miss the best shots. I thought about entitling this article series "Brute Force Photography" because that's what I do to get meteors.

Leave auto white balance on at first for simplicity. Work on getting good clear pictures of stars. You can experiment with the white balance to get the most pleasing (or interesting) night sky color once you've got the basic process down.

The lack of an infinity focus option on the NEX is the trickiest part of shooting at night for me, and probably the weakest spot of this configuration. I plan to buy an adapter and use manual focus lenses eventually. The reason I didn't mention this in Part 1 is because the adapter adds to the expense considerably, and I can't make specific recommendations yet. If you really get into it you'll spend as much as you did on the camera on more lenses and maybe more camera bodies. I may never get a telescope or equatorial mount because the opportunities for wide-field are endless and time consuming.

So you'll need to set your camera to manual focus (MF). The autofocus (and Direct Manual Focus on the NEX) will fail on a dark night. Look for a bright star or planet to focus on once everything else is set as specified above. If you pick a planet, you won't be able to focus it down to a pinpoint. Look for some adjacent stars to focus on to finer pinpoints. I sometimes zoom in and out digitally using the button under the NEX dial, and will pan around the sky using the dial as necessary. I move the focus ring slowly (being careful not to touch telephoto zoom ring) while I look for faint stars to show up that are fading in and out on the same place on the LCD display. You may see other random pixels blinking on and off that are just noise in the LCD display and not stars. It is easy to be fooled at first, but a little patience will tease out a few more stars on dark nights. I turn the LCD brightness all the way down before my night shoot begins, and also select a minimal information display profile to maximize how much real sky I see on the LCD.

You might have trouble finding a good infinity focus point at night if there's a lot of light pollution. The camera sensor sees a lot more in a long exposure than the LCD can display so lack of stars to focus on doesn't mean lack of stars to photograph. If clouds or light pollution mean you don't have stars to focus on for infinity, you can try to set it during the daytime using a point far away on the horizon, and then keep that setting for use at night. Or maybe at night there are lights on a tower on a horizon far enough away to serve the same function... that would be my last choice though, with stars being my first. Pinpoint stars are simply more discrete.

NEX users: before you change batteries, first turn the camera off and leave it off for about 10 seconds until you hear a slight click or whirring noise. Otherwise it may revert settings to a prior state that you don't want.

The single most important rule I can give is to review what you're doing as you go along. Don't just look at the preview of the photo, but click the center button on the NEX wheel and scroll up to near 100%. There will be a little streaking that you'll never completely eliminate due to the earth's rotation, but for the most part you should see points of stars in the center of your image, and not fuzzy balls. I look at both the very brightest and the very dimmest visible stars to determine how good or bad it is, and then tweak it either direction from that focal point a few times. Even when you think you've got it, check it again regularly as you go through your shoot. Particularly double check all settings after any battery changes, especially focus since you can more easily bump the focus controls in that process if you have to remove the camera from the tripod to change the battery.

When you're setting up, make it a habit to check the bubble level in your tripod. When you're reviewing your photos on the LCD make sure what is displayed there looks level too. I turn the rule of thirds grid display on and use it in my compositions (more or less).

I mentioned in Part 1 that an infrared remote is helpful for taking photos without touching the camera. If you didn't acquire one, the last thing to do before you take a photo is set the timer mode so that it will take a photo shortly after you press the shutter button. Try to make the whole tripod as stable and motionless as possible. There are vibrations in most decks you can't avoid, so solid ground is better if you have it.

One final thought: BULB mode can be used to take exposures as long as you want, and star trails aren't always a bad thing. I simulate long exposures using photos I take for time lapses:

This concludes my beginner's advice on technique for your first wide-field astrophotography shoot. I'm sure I've left something out, and some of this won't make total sense if you're new to photography. I wasn't even sure what aperture and ISO were when I began, but after enough background reading and experimentation I got a practical feel for them. Don't be afraid to play around with the settings... it's not like you can hurt anything (unless you zoom in on the sun and take long exposures... I avoid direct photography of the sun at any magnification without filters).

In a future blog I'll cover my technique for making time lapse movies. You might be surprised how fascinating time lapses of mundane things you already see (or don't see because they're mundane), can be. Even on the cloudiest days or nights, there is still the potential to make magic. I didn't shoot this video, but it's a good example of what I mean. Some of the stills used to make it may be interesting, but none could ever rival the finished video for conveying drama.

Note: this guide was originally published on my blog at Wilderness Vagabonds.

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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7:25 PM GMT on January 04, 2013
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Wilderness Vagabonds

About polymorph

I'm a reader, writer and troublemaker. Sometimes I take photos and make time lapse movies too.

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