You’ve seen those amazing images from the Hubble Space Telescope or from the myriad of internet sites that are full of fantastic images of the night sky, and you think to yourself, I want to do that. You can! Depending on what you want to photograph will determine the kind of equipment and the difficultly in obtaining that stunning shot. Obviously a space telescope would be ideal but that is beyond the budget of most of us.
The objects to photograph in the night sky can be broken into a few categories, such as bright stuff, dim stuff and the whole lot. Each of the the three categories requires a slightly different approach and different equipment.
The Bright Objects in The Night Sky
The bright stuff is the Moon and planets, and if you have a solar telescope then the Sun as well. The great thing about these photography targets is that they generate plenty of light so you don’t have to worry about tracking the object very accurately and you won’t need long exposures. To get the best image you need to take a lot of images to reduce the noise from each individual shot. This is best achieved by taking a lossless video, an uncompressed video format like AVI is ideal. If you are using a mobile phone this is not always possible and it’s not the end of the world if you are stuck with a compressed format, you can still get a great result. The idea is you take the video and try and get a few hundred to a few thousand frames. This is then run through a stacking application like AutoStakkert or Registax and you end up with a reasonable finished product.
There’s lots of things to consider when taking images of the Moon and planets, such as image scale – which is the size of the object in the image. This relates to the focal length of the optical setup and the quality of the final image is greatly influenced by atmospheric conditions, and how steady you can keep the image and how well you’ve focused it. All of those can be assisted by the use of specialist mounts that can track night sky objects and other attachments like a motorised focuser on the telescope.
The Dim Objects, That Need a Bit More Work
The next type of imaging is the dim stuff, this is trying to get those fantastic images you see of swirling gas clouds and majestic galaxies with their impressive spiral arms and vibrant colours. This is quite tricky to achieve as you need to collect as much light as possible but the problem is there isn’t much light at all. The photons that you are trying to collect have been journeying through space for, sometimes, tens of millions of years in every direction so not many of them make it to your sensor.
To collect as many of these illusive photons as possible you need to have the exposure open as long as possible. When this happens then there’s always the problem of keeping the telescope fixed on the object you are trying to image so you don’t end up with trails of stars or funny shaped objects. To do this you need a way of keeping the mount pointing at the exact same part of the sky all of the time whilst keeping up with the movement of the Earth. This is achieved by getting a very expensive mount or by having a setup which specifically aids in the guiding of the mount, usually a smaller telescope and camera which sends commands to the mount to keep it pointing accurately at the same spot.
The Whole Sky
The final type of imaging is the landscape or super wide field images that seek to capture the whole Milky Way and give those brilliant images that grace calendars and hang on walls everywhere. These are all about collecting as much light as possible in the shortest amount of time. Modern DSLRs have certainly helped this sort of imaging with very high ISO settings and low noise levels in the sensors. In the past the challenge was getting enough exposure to create a great image without seeing star trailing.
Where can you find out more?
At your local astronomical society, there’s always loads of astrophotographers eager to share their knowledge and help out people getting into taking photos of the night sky. Check the RASNZ website to see who’s local to you.
If you want to be inspired by some world class astrophotography, check out Mark Gee’s site.
We run astrophotography courses at Stonehenge Aotearoa as well, to get you started on the basics and show you what sort of equipment is required, follow us on facebook for further details or book here.