Ken Hough's Website
Projects: Barn Door Mounts -- for astrophotography
Earth rotates at almost exactly 15 degrees per hour (ie 360 degrees divided by 24 hours), causing stars to appear to move across the night sky.
Bright subjects such as the Moon can be photographed using short exposure periods, so that a statically mounted camera can be used to effectively 'freeze' the effects of rotation of the Earth. Less bright subjects require longer exposure periods, causing images from a statically mounted camera to be 'streaked'.
Streaking can be avoided by mounting the camera/telescope on a motorised equatorial mount. These mounts can be expensive.
There are many subjects in the night sky that are too wide to be accommodated within the field of view of a telescope. Ordinary short focus camera lenses are more appropriate for these subjects. These lenses, plus a camera are very much lighter than a telescope based sytem and so can be supported on a much lighter mount.
Instead of using a possibly expensive equatorial mount, an effective, economical, and very portable solution can be found with a home made Barn Door mount.
This section reviews some background literature and describes my own implementations and experiences of Barn Door mounts.
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