{"product_id":"tele-vue-5x-powermate-1-25-pre-owned","title":"Tele Vue 5X Powermate - 1.25\" - (Pre-owned)","description":"\u003cp\u003e\u003cspan style=\"color: rgb(242, 7, 7);\"\u003e\u003cstrong\u003eIn excellent condition\u003c\/strong\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003ccenter\u003e\n\u003ch2\u003eAbout the TeleVue 5X Powermate - 1.25\"...\u003c\/h2\u003e\n\u003c\/center\u003e\n\u003cp\u003eTo understand the \u003cb\u003eTeleVue Powermate\u003c\/b\u003e, we must first understand the \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003eBarlow lens\u003c\/a\u003e. Barlows amplify the power of a telescope. They can be considered \"focal reducers\" for eyepieces, or \"focal extenders\" for objectives. Terence Dickenson, in his Barlow test report in \u003ci\u003eSky and Telescope\u003c\/i\u003e says: \"Technology has erased the old objections. A modern Barlow will not degrade your \u003ca href=\"http:\/\/khanscope.com\/newEquipCart.cfm?catID=1\u0026amp;subcatID=1\"\u003etelescope\u003c\/a\u003e''s optics. Anyone telling you otherwise is using outdated information. Moreover, the highly regarded Nagler \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003eTeleVue Telescope Eyepiece\u003c\/a\u003e and their clones have built-in Barlows, ample evidence that the lens is not some detrimental intruder.\" Thanks, Terence, for laying the myth of the degrading \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003eBarlow lens\u003c\/a\u003e to rest.\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003eA high quality \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003eTeleVue Barlow Lens\u003c\/a\u003e must be properly designed and manufactured in order to avoid compromising a \u003ca href=\"http:\/\/khanscope.com\/newEquipCart.cfm?catID=1\u0026amp;subcatID=1\"\u003etelescope\u003c\/a\u003e''s color and spherical aberration corrections. The \"invisibility\" of Tele Vue''s 2-element Barlows has been noted in test reports in the astronomy magazines. However, by the nature of its negative power lens, a \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003eBarlow lens\u003c\/a\u003e will do more than just increase magnification, regardless of the number of elements.\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003eThe diverging rays leaving the \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003eBarlow lens\u003c\/a\u003e result in moving the exit pupil further out, thereby extending the eye relief. In short to medium focal length eyepieces the change is not noticeable. However, in the case of long focal length \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003etelescope eyepieces\u003c\/a\u003e, the increase can be significant and not without performance consequences.\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003eVignetting can occur due to the altered ray path, when the \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003etelescope eyepiece\u003c\/a\u003e''s lenses are not large enough in diameter to allow all the rays to make it through. Shorter Barlows, or ones with too much magnification, only exacerbate the problem because the ray path entering the eyepiece is steeper.\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003eTeleVue had to go beyond the \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003eBarlow lens\u003c\/a\u003e concept to achieve the goal of a compact, high power, fully corrected image amplifier. The Powermate consists of a negative doublet plus a positive \"pupil-correcting\" doublet. This 4-element system provides the magnifying function of a \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003eBarlow lens\u003c\/a\u003e without its limitations by restoring the field rays back to their original direction, as if the \u003cb\u003eTeleVue Powermate\u003c\/b\u003e were not there. The result is a pure magnification increase.\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e\u003ci\u003e\"While \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003eBarlow lenses\u003c\/a\u003e are powerful tools, the negative element defining them also limits their ability. The simple negative element Barlow increases eyepiece eye-relief. With short focal length eyepieces the effect is negligible. However, on long focal length \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003etelescope eyepieces\u003c\/a\u003e the exit pupil position moves well beyond the designer''s intended position, resulting in vignetting with many eyepieces. This is why \"Shorty\" Barlows in particular, with their strong negative element often vignette and degrade long focus eyepieces. My 4-element form picks up where the \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003eBarlow lens\u003c\/a\u003e concept can go no further. \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003eTeleVue Powermate\u003c\/a\u003e is a technically universal solution, using a positive field lens to redirect field rays. The result is an exit pupil that stays where the eyepiece designer intended. With freedom from aberrations, greater magnification potential, and compact size, I hope you''ll agree \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003eTeleVue Powermate\u003c\/a\u003e raises the standard for image amplification.\" --Al Nagler\u003c\/i\u003e\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003eBe sure to check out our line of \u003ca href=\"http:\/\/khanscope.com\/newEquipList.cfm?catID=1\u0026amp;subCatID=1\u0026amp;manID=7\"\u003eTeleVue Telescopes\u003c\/a\u003e, \u003ca href=\"http:\/\/www.khanscope.com\/accessList.cfm?catID=3\u0026amp;subcatID=13\"\u003eTeleVue Telescope Mounts\u003c\/a\u003e and \u003ca href=\"http:\/\/www.khanscope.com\/accessList.cfm?catID=3\u0026amp;subcatID=15\"\u003eTeleVue Telescope Accessories\u003c\/a\u003e. Don''t forget \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003eTeleVue Telescope Eyepieces\u003c\/a\u003e, \u003ca href=\"http:\/\/khanscope.com\/accessDetails.cfm?productID=5224\"\u003eTeleVue Dioptrx\u003c\/a\u003e and \u003ca href=\"http:\/\/www.khanscope.com\/accessList.cfm?catID=3\u0026amp;subcatID=10\"\u003eTeleVue Eyepiece Filters\u003c\/a\u003e, too!\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003ccenter\u003e\n\u003ch2\u003eTeleVue 5X Powermate - 1.25\" Features...\u003c\/h2\u003e\n\u003c\/center\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eVignetting, edge field aberrations and pupil movement - all introduced when using Barlows with long focal length eyepieces, are minimized.\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003eTelecentric operation (field rays leave parallel to optical axis, unlike Barlow lenses which diverge rays). This is ideal for Hydrogen-alpha filter use such as with Daystar models.\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003eHigh performance for image amplification, CCD or film.\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003eFlexible for visual and imaging with all types of telescopes and eyepieces. Essentially Parfocal, and with nearly constant magnification regardless of image distance behind top surface (except 5x model which increases 1x for every 35mm of image distance increase).\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003eHigher magnifications are possible with high optical performance compared to \"doubling up\" Barlows.\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003eAll will reach parfocal point in star diagonals, except for the 2\", 2x which comes very close.\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003eIn addition to full multi-coating, Powermates include other Tele Vue special touches such as safety undercuts where practical on the chrome barrel and captive lock screws that can''t fall out, and filter threads.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003ccenter\u003e\n\u003ch2\u003eTeleVue 5X Powermate - 1.25\" Specifications...\u003c\/h2\u003e\n\u003c\/center\u003e\n\u003cp\u003eEquipment Type: 5X Powermate\u003c\/p\u003e\n\u003cp\u003eBarrel Size: 1.25\"\u003c\/p\u003e\n\u003cp\u003eWeight: 0.40 lbs.\u003c\/p\u003e\n\u003cp\u003eWarranty: Limited Lifetime\u003c\/p\u003e\n\u003cp\u003eTeleVue Product Number: PMT-5126\u003c\/p\u003e","brand":"TeleVue","offers":[{"title":"Default Title","offer_id":43242913398897,"sku":"USED051403","price":251.1,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0851\/2766\/files\/485-1-thumb_1.jpg?v=1778781660","url":"https:\/\/khanscope.com\/products\/tele-vue-5x-powermate-1-25-pre-owned","provider":"Khan Scope Centre","version":"1.0","type":"link"}