Telescope uses are very wide, outdoor, travel, concert, military reconnaissance, sports events, all want to see the distant people and things can be used telescope.  Novice telescope selection will generally be more vacant, do not know the many parameters of the telescope which should be paid attention to, easy to be fooled by the business.  The first challenge you’ll encounter is choosing the right telescope that best fits your needs and budget.  What newbie should know about buying binoculars – This guide will help you get your money’s worth, rather than a telescope you’ll never be able to use after a disappointing first night.  

What newbie should know about buying binoculars

Caliber: Caliber refers to the caliber of the objective lens.  The aperture is directly related to the image of the object you observe.  The larger the aperture, the clearer and more detailed the object.  

Objective material: objective material is divided into gluing objective, double separation objective, and achromatic objective. Generally speaking, gluing objective is the cheapest and has the worst imaging quality. When observing distant objects, serious chromatic aberration will occur.  In general, unless you are on a budget, a dual-split objective is usually the best choice.  The achromatic objective is expensive because of its complex manufacturing process and expensive materials.  

Limit magnification: Limit magnification affects the maximum effective magnification of a telescope.  We think the limit multiplier is 2 times of telescope aperture commonly, for example, the telescope of 102/1000 model its limit multiplier is 200 times, however, this is to tell only theoretically, the optical quality difference exists between the telescope of the same model and different brand, a telescope of excellent optics can exceed limit multiplier 50 times or so!  Note that bigger telescope magnification is not always better!  Once the magnification exceeds the telescope’s maximum magnification, the image becomes blurred and details are lost due to inefficiency.  

Resolution: Resolution is the precision of the screen image, which refers to the number of pixels a display can display.  Because dots, lines, and planes on a screen are made up of pixels, the more pixels a monitor can display, the finer the picture and the more information it can display in the same area of the screen, the resolution is a very important performance indicator.  The entire image can be thought of as a large checkerboard, and resolution is represented by the number of points where all the longitude and latitude lines intersect.  

Focal length: Focal length is the distance from the main plane to the focal plane, denoted by F.  The ratio of focal length to the aperture is called focal ratio, expressed by F, and its reciprocal is called the relative aperture.  The focal length determines the line diameter of the focal surface.  The larger the focal ratio, the dimmer the image.  

Exit pupil distance: Exit pupil distance is the distance between the eye and the last piece of the eyepiece when the entire field of view can be seen.  Its size is very important for myopia patients who wear glasses. Although they can still see a clear image after taking off the glasses and refocusing, it is very inconvenient when they need to observe the stars alternately with the naked eye and binoculars repeatedly.  In addition, if people wearing astigmatism glasses take off the glasses, no matter how to focus are unable to see a clear image.  

To see the entire field of view with glasses, the exit pupil distance should be at least 14 to 15 mm.  When the exit pupil distance is less than 8 mm, even people without glasses can feel inconvenient to use.  

Entry pupil diameter: the object space where all light holes are projected into the first light hole, and the light hole conjugated by the “image” of the light hole with the smallest opening Angle of object point A on the axis is the aperture. The “image” of the light hole is called the incident pupil, which is referred to as the opening Angle of the square aperture of the object as “entry pupil” 2U.  The ratio of the entry pupil diameter to the focal length is called the relative aperture. 

 The entry pupil is the common entrance of the light beam from all points on the object’s surface.  The line between the object point and the center of the entry pupil is called the primary light, which also passes through the aperture and the center of the exit pupil.  The center of the entry pupil is the intersection of all primary rays.