Astrophotography Without a Telescope - 38

I love taking astro-images with my telescope, especially when I'm out in the field with fellow amateur astronomers - but sometimes I prefer to leave my telescope in its box and just shoot with my camera instead.

It's fun, it's simple and with a little experience you can achieve some interesting astro-photography. So, if you want to explore the night sky but you don't want the expense of buying a telescope, this article can be a guide for starting off in basic astro-photography without a telescope.

If I were to sum up the requirements for achieving worthwhile astro-images without a telescope in just one sentence, it would be:

"You need a dark sky; reliable photographic equipment which you understand how to use; and a good working knowledge of the celestial sky." 

There are no short-cuts to this formula.

ESSENTIAL #1: SOLID TRIPOD MOUNT.

DSLR camera with wide angle lens on tripod. Note the suspended stabilising centre weight

• To avoid wiggles and blurs, a tripod is absolutely essential for astro-imaging.
• It is common knowledge that hand-holding a camera during exposures longer than about 1/20th of a second will result in the image becoming blurred squiggles.
• Astro-imaging of faint night-sky objects requires even longer exposures, typically up to about thirty seconds. 
• An expensive camera will only produce the desired results if it is kept perfectly still during a long exposure.
• The tripod should be solidly built and extendable to about 1.5 metres.
• It should have smooth pan and tilt processes.
• Hang a weight below the tripod to keep it stable, reduce vibrations and provide low centre of gravity.

My Canon 60D DSLR with a 135 mm lens attached.

The basic camera requirements are: 

• Tripod attachment socket.
• Remote control socket.
• Long exposure capability (up to thirty seconds and/or bulb)
• Manual focus capability because auto-focusing was not designed for shooting the night sky and will almost certainly not work.
• Manual settings for shutter speed, f-stop and ISO adjustment.
• A lens hood helps to keep out local stray light and reduces susceptibility to dew.
• 'Live view' to frame the desired field and assist with manual focusing.
• A swivel monitor to achieve this without straining your neck.

ESSENTIAL #3: WIDE FIELD LENS

• Wide angle (low magnification) lens between about 10 mm and 50mm.
• Wide aperture lens (such as f/1.4 or f/2).

ESSENTIAL #4: REMOTE SHUTTER RELEASE

My old Canon 300D with remote shutter control intervalometer attached (right). The large grey button is the shoot button.

• To avoid vibration and movement, a hand held cord shutter controller is necessary.
• To take multiple images of the same object, use an intervalometer 

GETTING STARTED

• Using a celestial atlas, planisphere or computer software, determine which objects are visible at the time you wish to view.
• Set up and ensure the camera is firmly attached to the tripod.
• Attach the remote cord shutter release.
• Set the desired exposure time, aperture size and ISO.
• Frame the image
• Set the camera to manual focus and focus very accurately, using  electronic zoom on 'live view'.
• Experiment with your exposures until a satisfactory setting is achieved.
• The longer your exposure, the more light you let into the camera but the more likely you are to get trailing.
• The wider the aperture, the more light you let into the camera.
• The higher the ISO, the more light you let into the camera but the more grainy it might appear.
• There is a limit to how much light you can let into the camera if the sky is not dark, due to either light pollution, moonlight or early evening glow.
• Experiment to find a happy medium between the three variables.

MAGNIFICATION

• Amateur astronomers learn very quickly that wide field/low magnification yields the best views.
• Over-magnification will rarely produce worthwhile results.
• Stars will trail faster across the image during exposure.
• The ever-present atmospheric turbulence is magnified by powerful lenses and will turn pin-point stars into disappointing blurry blobs.
• Using a high magnification, narrow field lens will generally result in blurred stars.

• Hand-holding the camera instead of using a tripod.
• Using the camera shoot button instead of a cord shutter release.
• Unsteady or non-secure mount.
• Knocking the mount during exposure.
• Wind.
• Using auto-focus.
• Insufficient attention to manual focusing
• Excessive magnification
• High f-stop lens.
• Indiscriminate or random astro-targeting.
• Suburban light pollution.
• Moonlight.
• Street light or house light glare.
• Poor choice of exposure, ISO, f-stop settings.
• Over exposure or under exposure.
• Ignoring the effect of celestial rotation.
• Exceeding the 500 rule.
• Attempting to image faint objects in light polluted skies.
• Shooting JPG images instead of using RAW.
• Dew on the lens.
• Dirt, dust or smears on the lens.
• Excessive cropping of the object in post-processing, resulting in individual pixels enlargement.
• Lack of understanding of the relationship between shutter speed, focal ratio and ISO settings.
• Point and shoot cameras.
• Inadequate post-image processing.
• Over-enhancement in post-processing.
• The belief that you are shooting aliens in flying saucers.

CLOUDS & FOREGROUND OBJECTS

Star vista -  Click to enlargeme in a new tab

• Clouds, Earth satellites, aircraft or the Moon will often wreck astro-photography.
• However, with wide angle astro-imaging you can sometimes make these work to your advantage.
• Many of the best astro-mages include foreground objects.

">WHAT'S IN MY IMAGE?

• This is where a basic understanding of astro-photography is essential but in short you will see stars and planets with possible trails from aircraft and satellites.
• It is best to know which object you are shooting before you shoot it.
• The appearance of any object which you cannot identify is not evidence for aliens in their flying saucers or government conspiracies. 
• It just means you either don't understand the celestial sky or you don't understand your camera.

THE KEY

• The key to successful astro-imaging without a telescope is a solid mount, precise manual focusing and correct exposure combined with knowledge of the night sky and choice of target. 
• Use wide-field lenses with low magnification.

NEXT STEP

• Develop your own techniques.
• Join your local astronomical society for experienced tips and integrate them into your routine.
• Purchase a motorised sidereal tracking mount from your local astronomy shop.
• Learn how to enhance your images using software.
• If you fancy working with higher magnification, then to yield worthwhile results, invest in a decent astronomical telescope.
• However, even with a large 'scope, maximising the magnification is still not the key to success.

All images © R.Powell