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ntroduction to Astronomy 

Star Trail Photography

The simplest method for takingastrophotographs involves mounting a35mm camera on a standard cameratripod for wide-field "star trail" shots.The camera should have a "B" or "T"shutter setting for time exposures and a

cable release to lock the shutter open.Exposures can range from 30 secondsto 6 hours, depending on the length oftrails desired and the darkness of thesky. Lens settings are usually wide openwith the focus set at infinity.With a50mm focal-length camera lens, thestars become elongated after about 30seconds of exposure because of theEarth’s rotation. Film with an ISO(speed) rating of 200 or 400 is ideal forshort exposures; slower films (lowerISO ratings) can be used for star trailsof an hour or more.

Piggybacking Your Camera

If you have a telescope on an equatorialmount equipped with a motor (orclock) dr ive,you can tr y piggybackphotography.The camera rides"piggyback" on top of the scope

(coupled by a special adapter) and thepicture is taken through the camera’sown lens.The motor drive counteractsthe Earth’s rotation so that the starswill appear as pinpoints on the film

instead of streaks,as with a staticallymounted camera.Such long exposurewill reveal very faint objects, includingnebulae that are too faint to see withyour eyes. Piggyback photography offersthe amateur an opportunity to captureconstellations,the Milky Way, and largedeep-sky objects on film.The telescopeor guide scope can still be used tocheck the accuracy of the trackingduring the exposure.

Prime-Focus Photography

The Moon is one of the first objectspeople observe with their telescope. It

is also one of the easiest and mostrewarding to photograph.All that isneeded is a telescope, a 35mm SLRcamera without a lens,a cable release,and a T-adapter and T-ring for your typeof camera.These two adapters allow thecamera to be coupled to the telescopewhere the eyepiece would normally go.Using your telescope as a telephotolens in this way is called prime-focusphotography.

Photographing the Moon requires short

exposures - a fraction of a second,so amotor driven mount is not usuallyneeded, though one is required ifexposure times exceed half a second.For example, using an 8" Schmidt-Cassegrain telescope and ISO 400 film

on a half-phase Moon, the exposuretime would be about 1/125 second.Theamount of magnification you get willdepend on the focal length of yourtelescope.

Deep-Sky Photography

Prime-focus photography of deep-spaceobjects like galaxies and nebulasrequires much more skill.These objectsare very faint, so long exposures andguiding are necessary. It is best to gainexperience with piggyback and lunarphotography before attempting thismore challenging technique.

The basic equipment you will need is atelescope with a sturdy equatorialmount and accurate drive motor, a drivecontroller (also called a drive corrector)to make small corrections to thetracking speed during the exposure anda 35mm camera with a "B" or "T"sett ing. The camera will need anadapter and T-ring for coupling it,without its lens, to the telescope.Another important piece of equipmentis a guide scope or off-axis guider (SeePage 58), which allows you to follow aguide star during the exposure.You willneed to make guiding corrections,usingthe hand controller, to keep thetelescope tracking accurately.(This is

also true when piggybacking with longtelephoto lenses.)

More overleaf…

Astrophotography 

How to photograph the Heavens

The urge to capture on film what is seen through the

telescope’s eyepiece comes to all of us sooner rather than

later.

In the next few pages of the catalogue we have a range of

recommended accessor ies to further and enhance your

astronomical observing.Astrophotography, like the equipment

needed to achieve it, can be as simple or as involved as you

and your budget wish it to be.

Different astronomical objects will require different

techniques and equipment – from a camera alone, to a

telescope fully fit ted with all the high-tech accessor ies. But to

start – and do start simply, all you will need is a 35mm single-

lens reflex camera, fast film,a cable release and a tr ipod.

The basic rule is – start simple and learn by your experience,

with perseverance you can achieve remarkably high standards

and produce some stunning images.

Some basic techniques

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Astrophotography 

Eyepiece Projection Photography

Getting good pictures of the planets is achallenge. Extremely high magnificationsare needed to obtain an acceptableimage size of these small objects onfilm. High powers result in a dramaticloss of light and make focusing difficult.Also, gett ing sharp planetary imagesdepends on steady atmosphericconditions. Experienced planetary

photographers make dozens of attemptsto get just one good picture.

The most common method ofphotographing the planets is calledeyepiece projection. Unlike prime-focusphotography, an eyepiece is used in thetelescope to project a magnified imageonto the camera’s film plane.An adaptertube called a tele-extender fits over theeyepiece and couples the camera body(without lens) to the telescope.Theresulting focal length and f-ratio are

three to ten times those of thetelescope by itself.

Cameras for Astrophotography

For astrophotography, you need acamera that provides SLR focusing,interchangeable lenses, and full manualcontrol of exposure, including the abilityto make long exposures withoutrunning down the batteries. Some digitalcameras and camcorders can becoupled to telescopes to take picturesof the moon and possibly the planets.

However,digital cameras designed forterrestrial use cannot take longexposures of nebulae and galaxies; theysuffer too much electr ical noise.Instead,digital imaging is done with astronomicalCCD cameras that include specialcooling elements.

If you are interested in tryingastrophotography, we recommendthe book,

Astrophotography for the Amateur ,2nd Edition,

by Michael Covington.

About Film

Film selection is critical toastrophotography.There is a widevariety of films available,but some arebetter for astrophotography thanothers.Many astrophotographers preferto work with colour slide film ratherthan print film, so that they are not atthe mercy of the print-makers - filmcovers a greater brightness range than

paper can,so to improve a print thebrightness has to be adjusted. Withslides,you can see exactly what thecamera recorded, and you can getquality prints from them.

Phot ographic A dapt ors

To take astronomical

photographs through the

telescope you will need anadaptor. There are several

sorts from which to choose

depending on the type of

astro-photography you are

attempting.

You will also need a T-ring

which will enable you to

connect your SLR camera to

the adaptor. We stock mostpopular brand T-rings or you

can contact your local camera

stockist.

Basic Camera adaptorUsed for Prime Focus photography of the

Moon and Deep-Sky object

Projection Camera adaptorFor Lunar and Planetry photography

Projection Camera adaptor (SCT)For Lunar and Planetry photography

Off-Axis Guider (SCT)

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