About taking astronomical images

presented by Gianluca Masi, Ceccano (FR) Italy

To take astronomical pictures is one of the most appreciate activities between amateur astronomers. In despite of the instrument dimensions, an amateur can take great images, but for this there are several important indications. First of all, you need a motorized equatorial mount, in order to follow the stars in their motion, due to the Earth rotation. It is important that your mount (german or fork model) has an accurate mechanics. Then you need a system to control the guide during the exposure, so you can correct the errors due to your mount and motors. You can use, for example, a secondary telescope, parallel to the principal one, equipped with an illuminated reticle ocular. At the prime focus of your telescope you will attach your SLR camera, equipped with an appropriate (generally hight speed) film. If you take pictures of faint objects, as galaxies, you will take a long exposure: it is recommended to use a fast telescope, with a focal ratio of about f/5. Today amateur astronomers use CCD cameras, which offer great sensibility and more. The CCD camera is used instead of classical camera and it is connected to a personal computer. Because of the CCD high sensibility, you often have not to guide. This is a great advantage ! You can also process the image, obtaining unexpected results: today amateurs take perfect images using these new systems.Many of the pictures presented in my website have been taken using a little telescope (Vixen SP R-150S) and a CCD camera (SBIG ST-7). If you want to begin this activity, I suggest you to read a book about astronomical photography, available in every specialized store. If you need informations about the instruments, visit the Auriga and SBIG sites.