Astro photography
II


Deep Sky Set-Up

Deep Sky Set-Up. For longer exposures using higher magnification it's necessary to use a sturdy mount that can accurately track the motion of the stars during the exposure. I use a method sometimes called piggybacking, which has the camera riding along with a telescope on the mount. In this case, the optical tube assembly (OTA) is a Meade five inch Maksutov-Cassegrain, and it is fitted with an illuminated reticle eyepiece. This special type of eyepiece has illuminated cross-hairs which are used to keep a guide star perfectly centered in the field of view. Doing this means that the telescope, and of course the camera, will be pointed at exactly the same spot, and that the star images will be imaged without trailing. Fine adjustments to keep the guide star centered are made with the controller attached to the mount. Even though a mount may be accurately polar aligned with the Earth's axis, some guiding is usually still necessary. The mount I use is a German equatorial HEQ5.

The camera is attached with a tripod ball mount on heavy aluminum bar stock to the telescope mount. The ball mount gives more freedom of pointing and composing, so I'm not limited to just the guide star direction. The camera has an electronic remote shutter release so isn't necessary to touch the camera during the exposure. A battery powered kitchen timer (which I have to keep under my coat in cold weather!) keeps track of the exposure time, and a power inverter battery (on the ground) provides the 12 volt DC to run the mount motors.

The whole set-up is a fairly solid 60 lb. This gives a steady base for photography, but it's a bit too heavy and awkward to carry around in the dark, so the OTA, camera and counter weight are attached after the mount is set in place. Luckily my rural setting has very low light pollution so I don't have to carry things far — usually just my front lawn. Deep sky astro photography can be challenging. It is a bit like trying to get a detailed photograph of a coin from a kilometer away, with a half hour exposure, while the coin is moving! But it can be very rewarding as well.

Here's an example of a photograph made with this set-up.

Astro Photography Home Page
Steve Irvine
R.R. # 2
Wiarton, Ontario
Canada N0H 2T0
(519) 534 2175
email