Sun, 8. July 2012
Astrophotography Without a Telescope - 4
An article submitted to "Prime Focus" magazine.
During the final year of my period as MAS Secretary, I was “adopted” by a gentleman who found my phone number in The Macarthur Chronicle. He had a Powershot camera with a 35X zoom and occasionally he would wander outside into his front garden at night and point the camera at something bright. He would then take hand-held images at full zoom and send them to me with a request to identify them for him. The exposure times varied from about half a second up to fifteen seconds and - needless to say – most of the images showed all the hallmarks you would expect from an unsteady hand-held camera and were usually over-exposed and sometimes poorly focused.
I usually managed to identify the objects for him – as much from the details he sent as from the image itself. After all, when he told me it was a very bright object setting in the West in the early evening, Venus had to be the chief suspect. The satellites of Jupiter are easily identifiable too, even when slightly out of focus and with obvious vibration.
His images alone would have been totally unidentifiable without the time-stamp and his brief description of where the camera was aimed. However, I wanted to encourage him, so rather than be too critical, I would tell him what his image had captured and advised him politely to go out and buy a cheap tripod so he could keep the camera steady when taking exposures of a hundredth of a second or more.
That is the focus of this article, because anyone can be an astro-imager, if you can just keep the camera still while taking a night sky photograph. Using a tripod is the best way to do this and you can buy a flexible “Gorillapod” for as little as $20.00 or a more conventional extendable aluminium tripod starting at around $60.00. That's a cheap way to start off in astro-imaging and you don't need a telescope to do it.
What you do need is a camera which (a) has a tripod mounting socket; (b) allows you to take exposures of up to thirty seconds; and (c) has a manual focus, as most cameras have trouble focusing when aimed at the night sky. A cable shutter release attachment is also very desirable, allowing you to completely eliminate all camera vibrations when depressing the shutter button, if the camera is on a tripod.
If your camera meets this basic criteria and you have a tripod mount, then you can get started as an astro-imager!
What can you image from a tripod-mounted camera? Well, the various Moon phases for a start and I have also seen some wonderful Lunar images taken with a cityscape foreground. The Moon can occasionally look good among the clouds. I am still waiting to snap my first Lunar halo.
The planets Venus, Mars, Jupiter (and it's four Galilean Moons) and Saturn are easy targets. Mercury is possible, if you can track it down in the early evening glare. I haven't tried Uranus yet without a telescope (but it's on the list). Planetary conjunctions look great and you can take long-exposure images of the International Space Station and catch the next Lunar eclipse.
With a good zoom lens you can also pick up quite a few deep-sky objects such as M42 and Omega Centauri. Wide double stars are easy and if you have a good wide-angle lens you can snap some great Milky Way images.
My first astro-images were of Comet Halley, taken on ISO 1600 film in 1986. Despite my best efforts, they are not very good images but at least I tried - and not too many people I know have their own images of the famous comet. After a long time gap, I started taking Lunar images in 2005.
Of course, it always helps if you can shoot in a dark-sky location, well away from the city lights! Oh, yes, you also need clear skies!
Milky Way. Canon 60D, tripod, 10mm lens, 30 sec, f/3.5, ISO 6400 (RP)
So how did my friend go with his hand-held images? Most were not up to scratch but he got some half-decent images of Venus, Jupiter and it's Moons and Alpha Centauri – but at least he's having a go!
So check your camera, buy yourself a tripod and a remote shutter release and start snapping the Solar System. Not all astro-photographs have to be faint wispy, deep-sky nebulae!
It's easier than you think and it's never been so cheap!
This article was published in "Prime Focus" magazine (the journal of Macarthur Astronomical Society), July 2012 edition.
Astro-images look much better when enlarged! Please go to my MAS Members Images Pages and view them full size.
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