Please note that all values is given in arcminutes.
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Focal ratio is the ratio between the apertude and the focal length of your telescope. The ratio is marked f/ and is directly comparable with the iris in an ordinary camera. If you want to calculate the values with barlow-lens, multiply the focal ratio with the magnification of the barlow.
Focal length of eyepiece is usually marked on the eyepiece. Comes always in millimeter.
Apparent field is marked in degrees. If the apparent field is 10-20° it will give you feeling of looking down a long tube. But if the apparent field is about 80° you will almost have to crepe down in the eyepiece to see it all. The manufacturer of the eyepiece give the apparent field in their technical data.
Camera gives you the oportunity to choose the camera you want. It can be a SLR-camera or a CCD-camera.
Focal length is the distance from where the light is first bent till it meets in focus.
Magnification is by many considered as the most important thing at the telescope. The magnification is rather insignificant, but is convenient for comparing preformance of different telescopes.
Exit pupil is the diameter og the lightbeam that exits the eyepiece. If the exit pupil is larger than the pupil og your eye, you can manage with a smaller telescope. In most cases observing with less than 1mm exit pupil will not work.
Field-size is maybe the most important thing of all. It gives you an idea of how big path of the sky you are looking at. Field-size is messured in degrees and arcminutes. The distance from the horizon to zenith is 90°. The apparent diameter og the moon is 0.5° or 30' (arcminutes).
Primary focus gives you the image-field in the telescope with the chosen camera.
Pixelcoverage is maybe a little odd. It describes how many arcseconds each pixel of the CCD-camera covers. In Norway it is hard to see details smaller than 1-2 arcseconds. Better pixelcoverage than this is therefore unnessecary. The exeption is for planetary work.
Circle of eyepiece is the size of the circle you put in the star atlas to match the field in you telescope.
Rectangle of camera er the size of the frame to match the camera-image in the chosen star atlas.