For the April 2018 Astrophotography Highlight I’m going to go for some low hanging fruit and talk about shooting the moon! If I had a dollar for every time I’ve heard a fellow astrophotographer lament that the moon was up… well, I could probably buy the moon! The moon was my first love and is to me one of the most amazing targets in the sky that you can shoot; it is also the easiest. No matter what kind of camera, optics, or mount… and this includes TRIPODS, you can get great images of the moon you can be proud of!
The moon was the gateway drug that got me started in astrophotography as a whole taking photographs of the moon through my telescope as if it were nothing but a very long telephoto lens. It is a great (possibly the best) way to get started in astrophotography because you can get results you will be happy with your very first night out. The moon is available all year long, it shines through the worst light pollution any city can muster, and it’s a fascinating world that changes nightly! You can even with some success photograph the moon through very thin clouds or haze.
You could spend a lifetime exploring the moon (photographically or visually). Once I watched the same crater for several hours one night, and you could see the changes over the course of as little as an hour. Because of libration (the monthly “swivel” of the Moon) you’ll see different features along the limb each month, and even features not near the limb (edges) can cast different shadows that can only be seen every few months.
There are many great ways to get started in lunar imaging. Let’s go quickly over a few of them.
Use a Cell Phone
The most common way people take photographs today is with their cell phone cameras, and just about everybody has one. You can literally hold your cellphone up to a telescopes eyepiece and take a photo. It takes some practice, but I’ve seen teenagers do it on their very first try at outreach events. One trick is to rest the phone on the eyepiece cup to keep it flat and steady. You’ll find quickly that moving to the left actually moves the image to the right, etc. but after a few minutes you’ll get the hang of it. Often when there is a group of people, it becomes almost a game to see who can get the better shot. There are also many brackets on the market designed to hold your cell phone steady so you can take a photo directly.
DSLR or Point and Shoot
The most economical entry point for any serious photographer is the so-called “Point and shoot” camera with a fixed lens system (the front lens cannot be removed and is not interchangeable). Put this camera on a tripod, and with an optical zoom, you will easily get full images of the Moon showing craters, Maria, and ray systems in great detail. You can also try holding this in front of an eyepiece, or purchase some commercially made brackets that will hold your camera in front of the eyepiece for you. The same applies to a DSLR with a long lens, except this is more difficult to mount in front of an eyepiece. I’ve shot many lunar eclipses this way, and you can make interesting nightscape images by framing up a large moon with some distant landmark.
DSLR on a Telescope
You can also find very inexpensive adapters that will mount your DSLR directly to a telescope. The lens comes off the camera, and the adapter connects to your camera just like a lens would, but then slides into your telescopes draw tube. Essentially, the telescope becomes a large telephoto lens.
If you don’t have a remote release cable, turn on mirror lock, and set an exposure delay. Typically I will set the camera for a 10 second delay with mirror lock enabled. Then when I fire the camera, the mirror comes up, and there is a delay before the image is taken. This delay gives everything a few seconds to stop shaking/vibrating and you’ll get steadier images. If your camera does not have mirror lock, you can achieve much the same thing by using live view. Live view however tends to warm up the imaging sensor, introducing more thermal noise so I tend to stick to the previous technique.
Yes, you can shoot the moon with a CCD camera too, although now you need a computer to control the camera! Some CCD’s are so sensitive compared to a DSLR that you can’t get a good image without over saturating. Sometimes this is due to the fact that the shutters on these cameras were designed for long exposure purposes and you simply cannot get the exposure short enough. There are two solutions to this; the first is simply to stop down the aperture of your telescope with a mask at the front. The second is my favorite… use a red or narrowband filter! A red filter (if you have a monochrome camera with filters) will reduce the light considerably, and might improve sharpness of your monochrome image because the red wavelengths are less affected by seeing conditions than the blue and green. If you have a hydrogen alpha, or sulfur filter, use those! They cut down on the light even more, and also have that advantage of helping to mitigate the seeing due to their long wavelengths.
A live view of the moon is also a compelling outreach tool. You don’t even have to be scope side to slew around the surface and show off the moon to a room full of people. Video captured at long focal lengths can also be processed to create stunning high-resolution images using a technique call “lucky imaging”. This is perhaps extreme lunar photography in that it does require a good bit of work using special software to pick out just the sharp frames from the video file and combine them. Never-the-less, it’s still a lot less work to process than the typical deep sky photo!
Any of these methods are within reach of even the most inexperienced beginning astrophotographer. It’s also a great way to get your feet wet processing images just by tweaking levels, curves, and sharpness. I’ll talk about each of these different approaches to lunar photography in turn in future blogs here, or in my Sky & Telescope blog on imaging foundations.