Tracking the stars with a Black&Decker Workmate for long Exposure Astrophotography

How to Solve The Rotation Problem.

To overcome this you have three alternatives. (1) spend 100's to buy a rotating camera mount,
(2) build your own with wood, hinges and screws (known as a 'Scotch mount'),
or (3) use what many people already own: the versatile 'Black and Decker Workmate' which is used for numerous DIY jobs.

The only modification is to remove one bolt so that the moving board pivots around a single bolt as one of the handles is turned. The table should be used in the lower position so that it does not overbalance when it is tilted to point the pivot bolt towards the north star. Alignment of the bolt with the north star can be carried out using a magnetic compass and spirit level. My particular model of Workmate requires the handle to be rotated at 160 per minute such that the board rotates clockwise viewed from the north star. The system can be checked, in daylight, by ensuring that a pinhole image of the sun mounted on the moving board remains stationary as the handle is turned at the correct speed. The Workmate provides a stable platform for photography but be aware that being made of steel it will affect the magnetic compass and that the table moves two thread pitches per handle rotation! (my letter published in Astronomy Now magazine Vol 11 no7 p10 ISSN 0951-9726 Jul 1997)

Sam's animation
What is the rotation problem?

Imagine standing at the north pole at night and imagine that the earth is spinning fast like in the picture.
Look directly up, now all the stars are rotating in the opposite direction about the north star (Polaris). This is how a camera with long exposure sees it, making each star appear as a short line on a photograph, and faint stars are not visible at all.
To make the stars appear stationary, the camera must be on a platform rotating in the opposite direction. The platform can be anywhere on earth but must always rotate about a line pointing at the north (or south) star.

Comet Hale-Bopp Apr1997 Comet Hale-Bopp in Perseus 18Apr1997 setting at the rear of my inner city (Bristol, England) garden. Standard 400ASA,35mm compact camera with 10 mins exposure, hand guided by turning one handle of a Workmate. Note the Houses have rotated and the stars have stayed still, which is of course what really happens!
Comet Hyakutake Mar 1996 Much longer exposures/faster film can be used away from the light polluted cities giving much more detail in the night sky. This picture of Hyakutake I took in the very dark skies of Portugal. Ektarchrome1000, same cheapo camera as above, 10mins exposure but using a commercially available rotating mount. (I didn't take my Workmate to Portugal!)
Corona Borealis Aug 1994 Constellation Corona Borealis (Aug1994). Details as above (SLR camera), but a flash gun illuminated the trees at the end of the 10 min exposure so that the trees did not 'trail' (I did not see the phone wires in the dark!!) Photo taken as above at COAA an Observatory in Portugal where anyone with an interest in the night sky can stay
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back to home created May 1999, last update Jan 2002