bangs for your buck. The telescope is an ideal secondhand buy because it generaly arrives on the secondhand market for the simple reason that the first owner has had little time to use the instrument. On the secondhand market it is best to try to find a nearly new example that is in as new condition, comes with its original packing and has its full compliment of accessories including a support system of mount and tripod, eye pieces and if applicable, filters. On many occasions the first purchaser will have been persuaded to add to the accessories or sometimes upgrade to better ones. A word of caution however, a telescope that has been dropped or damaged may well have had its optical components knocked out of alignment. This can be a simple problem to fix if the telescope is designed to be adjusted from the outside. Many types of telescope need to be stripped down to be adjusted and this is a job for an expert and will add greatly to the cost of the instrument. With a simple refractor telescope the alignment can easily be checked by looking througt the wrong end of the telescope, the object lens. If the internal lenses appear to be in a series of concentric circles then the telescope is probably properly aligned. The other simple way of checking for alignment errors is to try to focus the telescope on a fairly close object.
There are many different types of telescope with the simplest and most recognisable being the good old fashioned draw telescope. This comprises a set of tubes that slide inside each other to adjust the focal length of the instrument and focus the telescope. There is a largish object lens but the maximum size is goverened by the fact that these are made primarily to be hand held so that to keep the image steady the weight of the scope needs to be on the low side. In the simplest draw telescope there is a fixed eye piece. More sophisticated models may have interchangeable eye pieces to give a range of magnifications. These telescopes are often quite old and leather bound to give a better grip and make it easier to hold steady. It is quite possible to mount such an instrument on a tripod to keep it as steady as possible for bird watching or target spotting on the ranges.
Other types of telescope are designed for different purposes and may use a combination of lenses and mirrors to enlarge the image and show greater detail. In the real world any optical telescope can be used for any purpose. Looking at the moon with even a low powered draw telescope will show craters and other features in great detail. Looking at the moon through a telescope designed for astronomical use brings out even more detail.
Take a look at www.secondhandtelescopes.com – packed with hints, tips and bargain secondhand telescopes.