Capturing the Night Sky
2016-06-27 17:44:04.000 – Meredith Campbell, Summit Intern
Reaching for the stars
One of the most unique things about interning at the Mount Washington Observatory is the fact that we are on the summit at night. As a total space nerd, the number of stars you can see from the summit on a clear night takes my breath away. This time of year also happens to be the best time to see the Milky Way (just like the constellations, the view of the Milky Way changes seasonally). For the past few months I’ve been focusing on developing my skills as an astrophotographer, and last night was my first opportunity to really put my skills to practice here on the summit.
One of the most amazing things about night sky photography is that it reveals things that we can’t see with our own eyes. We look into the darkness and perhaps we see a few stars, but for the most part it looks empty. But when you take a long exposure photograph all sorts of dim objects become visible, then you can look back at that dark sky, and even though you may not be able to see all the stars, you know that they are there. That is inspirational to me.
Also look at the really cool stuff you can capture! Visible in the photograph below are two airplanes, one satellite, and ANOTHER GALAXY! Can you spot it?
NH State Park intern Dan Farley practicing his own night photography
There may be some folks that want to try night sky photography but don’t know where to start, or maybe they assumed it was too difficult. While the quality of any astrophotograph relies heavily on the quality of the equipment and sky conditions, almost anyone with a DSLR can start learning the basic steps and produce photographs nice enough for personal use or social media.
I am still a novice for sure, but I have learned a few things this year that might help anyone who wants to try taking some pictures of our night sky. So if you’re thinking of trying out some astrophotography this summer, here are some basic tips to help you get started.
You will need a DSLR camera with the option to control the settings manually. Obviously the best cameras for low light are more expensive than cameras that are not as good in low light, but you don’t need an expensive camera to get started. I use a Nikon D3100, which honestly is not a good low light camera, but I can’t afford multiple cameras. I purchased my camera for regular photography, and I make due with its low light ability. After a few months of dedicated practice, I am certainly ready for an upgrade, but it was a decent camera to learn on.
The best cameras for astrophotography can record RAW files, have full sensors as opposed to cropped sensors (my camera has a cropped sensor), and they have more options for ISO settings. Your lens is also very important. You want as wide of a shot as possible, and the fastest lens possible (this affects your f-stop). Again I use the stock lens that came with my camera, which allows me to take an 18mm shot at f/3.5. If you’d like to know more the internet knows a lot about this stuff.
Really the only thing you NEED to get started is a DSLR camera, but a sturdy tripod will help keep the camera from moving during the whole exposure. If you don’t have a tripod, you can use a bag of beans or rice to position your camera (though not as sturdy as a tripod). I literally took this picture by putting my camera in the grass:
Using the grass instead of a tripod
If you think astrophotography is your new hobby, you definitely need to invest in a good tripod, but if you’re just testing the waters you can absolutely start without one.
The only other thing you might want is a remote trigger. When you push the shutter button on your camera you might actually shake the camera a little at the beginning of your exposure and that can blur your image. I don’t have a remote shutter, so I use the self-timer function, so that my finger is off the shutter button BEFORE the camera starts taking a picture. Again, don’t feel the need to go out and buy new equipment.
The darker the sky, the better the stars. Try to set up in a location with minimal light pollution, because it might be hard to believe but that city 50 miles away will definitely show up in your pictures.
You absolutely want to use manual settings with manual focus when you’re taking pictures of stars. Again use the fastest f-stop that you can. I use f/3.5, but the lower the number the better. If I could use f/2.8 I would. The shutter speed will change depending on the camera, but a basic rule for beginners is take the longest exposure possible before star trails start forming (your stars start looking like lines instead of dots). The last thing is to adjust your ISO setting. Ideally you want your ISO to be as low as possible, because the higher the ISO the grainier the photograph. But you also don’t want to be stingy with your ISO. What’s the point of taking pictures of the night sky if you can’t see anything? What I do is set my f-stop to f/3.5 and my shutter speed to 25 seconds (the limit of my camera) and then I set my ISO to ISO 800. If that’s too dark I change to ISO 1600 and take the picture again. Again if my picture is too dark I increase my ISO again. I personally never shoot higher than ISO 3200, because my camera is not made for low light and the image quality is seriously affected, but higher quality cameras can handle much higher ISO.
To photograph stars, you want to focus your lens to infinity. It’s a little confusing, but a lot of lenses aren’t at infinity if you turn your focus all the way in one direction. To focus my camera, I zoom all the way in on the brightest star in the sky and then manually adjust my focus. I then VERY CAREFULLY zoom back out, and then my camera is in focus. This won’t work for everyone, but it’s the way I do it.
Put your camera on your tripod, and set up what you think will be a nice shot (some guesswork involved). I actually hang a weight from my tripod to help weight it down (to prevent shaking in the wind). Press the trigger, and hopefully you’ll get something like this:
Unaltered photograph of the Milky Way using 25 second exposure, f/3.5, ISO 3200.
I’m not going to go into a lot of detail about how to post-process, but I think it’s important for newcomers to understand that post-processing is necessary for the night sky photos you’re accustomed to seeing. I don’t care how expensive someone’s camera is or how well they can compose a shot, everyone needs post-processing to produce proper night sky photos. Again the internet knows everything about post-processing, so I recommend watching a few instructional videos on the topic. Just don’t be discouraged if the pictures coming directly out of your camera aren’t what you were hoping for. As long as the information is recorded somewhere in the photo, you’ll be able to bring it forth after the fact.
As an example:
Unaltered photograph of the observation tower using 25 second exposure, f/3.5, ISO 1600.
Same photo as above after post-processing.
I know this wasn’t a comprehensive lesson, but I hope it was enough information for anyone who’s been wanting to try astrophotography. Hopefully this will encourage you to go give it a try. From one astroadmirer to another, good luck!
Meredith Campbell, Summit Intern