{"id":182,"date":"2023-10-14T18:39:15","date_gmt":"2023-10-14T17:39:15","guid":{"rendered":"https:\/\/www.gary.bilkus.com\/wordpress\/?p=182"},"modified":"2023-11-22T08:36:58","modified_gmt":"2023-11-22T08:36:58","slug":"eyepieces","status":"publish","type":"post","link":"https:\/\/www.gary.bilkus.com\/wordpress\/eyepieces\/","title":{"rendered":"Eyepieces"},"content":{"rendered":"\n<p>Thanks to the helical focuser on the finder\/guider scope in Vernet, we can accurately tell the difference in focus position for various eyepieces etc as follows.<\/p>\n\n\n\n<p><\/p>\n\n\n\n<p>Furthest in is the USB camera I&#8217;ve adapted so call that position 0<\/p>\n\n\n\n<ul><li>Svbony graticule                                                           +6mm<\/li><li>Altair ( when inserted up to the end of the blue part ) +10mm <\/li><li>Meade cheapo 25mm eyepiece                                    +13mm<\/li><li>Pentax zoom ( varies slightly with focal length )          +16mm<\/li><\/ul>\n\n\n\n<p>What&#8217;s also worth knowing is the field of view available from everything.<\/p>\n\n\n\n<p>That depends on the telescope too of course<\/p>\n\n\n\n<p>But if we know the flt of the telescope, the fle of the eyepiece and the apparent size of the view in degrees avdeg, then fov = avdeg * fle \/ flt<\/p>\n\n\n\n<p>For a sensor, of course, that doesn&#8217;t work, and we need the alternative:<\/p>\n\n\n\n<ul><li>fov = 2 * arctan (S \/ 2f),<\/li><li>where S is the diagonal size of the sensor in millimeters, and<\/li><li>f is the focal length of the lens in millimeters.<\/li><\/ul>\n\n\n\n<p>Of course for a telescope arctan is more or less the same as angle in radians, so the simpler formula<\/p>\n\n\n\n<p>fov = S\/f * 60 is good enough<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Thanks to the helical focuser on the finder\/guider scope in Vernet, we can accurately tell the difference in focus position for various eyepieces etc as follows. Furthest in is the USB camera I&#8217;ve adapted so call that position 0 Svbony graticule +6mm Altair ( when inserted up to the end of the blue part ) [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[14],"tags":[],"_links":{"self":[{"href":"https:\/\/www.gary.bilkus.com\/wordpress\/wp-json\/wp\/v2\/posts\/182"}],"collection":[{"href":"https:\/\/www.gary.bilkus.com\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.gary.bilkus.com\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.gary.bilkus.com\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.gary.bilkus.com\/wordpress\/wp-json\/wp\/v2\/comments?post=182"}],"version-history":[{"count":2,"href":"https:\/\/www.gary.bilkus.com\/wordpress\/wp-json\/wp\/v2\/posts\/182\/revisions"}],"predecessor-version":[{"id":193,"href":"https:\/\/www.gary.bilkus.com\/wordpress\/wp-json\/wp\/v2\/posts\/182\/revisions\/193"}],"wp:attachment":[{"href":"https:\/\/www.gary.bilkus.com\/wordpress\/wp-json\/wp\/v2\/media?parent=182"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.gary.bilkus.com\/wordpress\/wp-json\/wp\/v2\/categories?post=182"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.gary.bilkus.com\/wordpress\/wp-json\/wp\/v2\/tags?post=182"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}