Do you think getting started in DSLR astrophotography is too complicated or expensive? Perhaps you remember looking at the moon for the first time through your friend’s telescope. “Oh WOW,” you exclaimed! Without hesitation, you instinctively pulled out your phone, held it up to the eyepiece, and snapped a picture. You likely ended up with something like I did:
You didn’t feel it at the time, but the Astro Bug bit you and it sounded like fun! Then you read about telescopes on computer-controlled tracking mounts with monochrome cameras using RGB filters, image stacking, calibration frames, and star alignment. Whoa, slow down there!
Have What it Takes?
Take a deep breath and consider starting simple. The WORST astrophoto is the one you did NOT take. You can take beautiful astrophotos with the simple gear you may already have:
You probably have a DSLR (Digital Single-Lens Reflex) camera for taking pictures of the kiddos. The one above is by no means acutely suited to DSLR astrophotography. It’s just your run-of-the-mill personal camera. It does have some key features that can enable you to take star pictures though. See if yours has these basic requirements:
- Manual controls for exposure and ISO.
- Wide-angle lens (18mm – 24mm works.)
- Manual focus.
- Ability to turn OFF noise reduction, image stabilization if equipped.
- Option to save RAW images vs JPG.
*Pro-tip: Spend some time getting to know where these settings are on your camera. You won’t look like an amateur fumbling through menu options, searching for buttons out in the dark.
You need a tripod. You’re not John Wayne, so you won’t be able to hold the camera still while you take a picture. A fancy tripod is not required to take star pictures. Look for a tripod that will hold your camera, pointed in the direction you want, without shaking.
Set your camera to manual mode so you can control the focus, exposure, and ISO. No auto settings in DSLR astrophotography!
It’s time to focus…your camera. It’s dark, so autofocus will not do you any good. With your camera in manual focus, pick out the brightest star or planet you can see. If you can focus your camera while looking through the viewfinder great, but stars are small. It may help to zoom the live view so you can really get the best focus on that bright star. Live view can be dark. You will probably need to manually adjust the ISO setting as high as possible. Try ISO 6400 or higher. Also, if you have any aperture settings, those should be as wide (low number) as possible. If you still can’t get focused on the star, try to find a bright light. Look for the light on top of a radio tower and focus on that. The farther away the better!
*Pro-tip: Don’t forget to take the lens cap off.
ISO vs Exposure
Once your star or light is as focused as you can get, it’s time to take your image. There are two settings that you can change to capture an image that will show stars. ISO and Exposure. Both settings will make your image brighter by increasing their values but in different ways. I’ll spare you the technical mumbo jumbo that you don’t care about. You can think of ISO like a megaphone. A megaphone makes your voice louder (or in this case, the picture brighter). Like a megaphone though, while your voice is louder, it doesn’t sound as rich or clear. The same happens when you raise the ISO setting on your camera to a higher number. You’ll find that with a higher ISO your images appear grainy.
This is because while increasing the light signal, ISO also increases the noise at the same time. Most cameras have built-in noise reduction algorithms that can smooth this out. However, if you were following along, we turned that off. Why? Because the camera tends to treat tiny dim stars as if they were noise and filters them out too; No Bueno! For this reason, a longer exposure setting is preferred to leave the shutter open longer and gather more light. One problem, though, the sky is moving. Yes, more precisely, WE are moving! Your tripod and camera are sitting still while the sky, just like the Sun and Moon, is rolling right along. So, if you expose long enough, the stars will end up making a streak across the frame.
If this is what you’re going for, then great! You just got your first lesson in star trail images. Some find these star trail pictures to be very creative and interesting. If you’re just getting started in DSLR astrophotography, your friends will be impressed. However, if you want the stars to look like stars, you need to limit your exposure time. The good news is, trailing can be predicted with math (or as the English would say maths). The most common way is the simple “rule of 500.” Take the number 500 and divide it by your focal length times your sensor crop factor. I’ve been using my 18mm lens, Canon EOS Rebel SL1 camera, and APS-C type sensor with a factor is 1.61. The rule of 500 goes like this:
500 / (Focal Length x Crop-Factor) = Ideal Shutter Speed
So in my case:
500 / (18mm x 1.6 Crop-Factor) = 17.2532781 seconds
*Pro-tip: if you don’t know the crop-factor check this comprehensive database of camera specs here: Digital Camera Database
The rule of 500 isn’t exactly science (although there IS some thoughtful consideration behind it). We can calculate 17 seconds before the stars start to trail out of control. With today’s high megapixel cameras, that really is the LONGEST you would want to go with this lens/camera. Zooming in, you’ll still see trailing stars. However, most of the time, that’s not how the image will be displayed.
You could also use an app or website like Photopills to do this for you:
Getting to First Light
With our ideal maximum exposure calculated, we can take a shot for as long as possible. Then adjust the ISO up or down to get an image bright enough to see stars. Start with an ISO of about 1600 push your shutter button halfway down and see what your exposure meter thinks. I generally find that my camera, right on the center of the meter is a good starting point. Sometimes I bump up the exposure or ISO until I’m about 1 stop above the center.
If your camera has a built-in histogram function, it can help get the right exposure. You may need to press INFO or a similar button repeatedly to see the histogram pop up. Generally, a good target to shoot for is a peak around 1/3 of the graph. At the very least, there needs to be a separation of the hump from the left side.
A histogram that is clearly separate from the left side of the graph will result in a better-exposed image:
This is where you get to play with your camera setting because one size doesn’t fit all. You want to find a balance between exposure and ISO. Your picture shouldn’t be too grainy, and no trailed stars. Keep in mind that your image may look a little dark on the LCD and the computer. You are shooting in RAW format, so there’s a lot you can do in post-processing (guide coming soon).
After a few tweaks in Lightroom or your favorite RAW photo editor, your image will show much more detail than you may have seen on your camera’s LCD.
Mo Money, Mo Problems
Lots of expensive things can be bought for DSLR astrophotography. Some are worth the investment, others are just “nice to have” and some are a total waste of money. All the fancy equipment in the world won’t make bad images better. I did find that the program Adobe Lightroom was worth the investment. Plus LR isn’t specific to astrophotography and it can be used to make adjustments to all the photos you take. As of the writing of this guide you are still able to purchase the standalone version of LR if you’re not crazy about yearly subscriptions. There ARE free programs that let you do much of the same adjustments to your RAW photos. One example is Paint.net which is a free photo editing program I use often. Stop by my gallery to see more. Good luck and I hope you have clear skies!