It may take you some time to find a target and focus on it. Insert the lowest power eyepiece (the one with the biggest number on it – often 12.5) See if you can get some sort of a decent image with the telescope. Do not look through a closed window or screen. If you make the purchase, take the time to jury rig a device that will allow you to support the telescope temporarily while you aim it at a distant street light, mountain or building. Always check the optics of a telescope before you invest any time or additional money in trying to fix one up. Sometimes they are quite useless even though originally they were functional. Sometimes telescopes that you see at flea markets have been tampered with. I’ve seen telescopes like this selling for as much as fifty dollars. If it’s smaller than 2 inches, you should probably forget it. Also, the main lens should be at least two inches across. If there is a ring like this farther down the tube ignore it, it’s no problem. Be sure you see an actual aperture-stop right behind the lens, that blocks light from the sky.
Be careful, reflections can sometimes look a lot like these rings. If you see a ring immediately behind the main lens that blocks all but a small circle of light then you should not, under any circumstances buy the telescope. Look “down the throat” of the telescope (through the front where the main lens is found). If you are considering a purchase of one of these “Department Store Telescopes” you should check the optics first. Sometimes you can fix one of these small telescopes so that it delivers good views for its size and price. The deficiencies of these scopes are the mount, the eyepieces and the finder scope. The tube and focuser are useful and the star diagonal (used for right-angle viewing) is OK. Usually the objective(main lens) is reasonably good. What if you run across one of these telescopes at a garage sale? Should you buy it? Do these telescopes have any favorable qualities? Yes, they do. But more often, with telescopes, you will see the typical “Department Store Telescope” like this. People sell junk for high prices and give away unrecognized gold! Sometimes you run across a good buy. You can make improvements to your telescope that will make it more useful.
If you already have one and it’s too late to return it, read on. You cannot see anything at this power with this telescope.Ĭheapo Telescope Do Not Buy One of These Telescopes New! The high power of the instrument comes from a 4mm or 6mm eyepiece of cheap design and one or more Barlow attachments for 2x or 3x more magnification. There is a conspicuous absence of slow motion controls. The telescope is attached between the two prongs of a flimsy alt-az mount (the telescope moves up and down, side to side). It shines! It glints in the sun! It is guaranteed to dazzle any child! It touts high power on its box: 200 power, 400 power, 600 power, 1,000 power! It has a mount with thin spindly legs. You will recognize its distinctive traits. This ubiquitous telescope sells new for $80.00 to $150.00 in discount stores, department stores, camera shops, on the internet and even in “educational” toy stores. This is what we call a “Department Store Telescope” Among amateur astronomers, these are infamous for their long list of deficiencies. You can make improvements to your telescope that will make it more useful.” – Dave Trott “If you already have one and it’s too late to return it, read on.
0 kommentar(er)
