{"id":394,"date":"2008-01-30T23:26:58","date_gmt":"2008-01-30T23:26:58","guid":{"rendered":"http:\/\/perezmedia.net\/beltofvenus\/2008\/01\/30\/measuring_doubl_1\/"},"modified":"2008-01-30T23:26:58","modified_gmt":"2008-01-30T23:26:58","slug":"measuring_doubl_1","status":"publish","type":"post","link":"https:\/\/perezmedia.net\/beltofvenus\/2008\/01\/30\/measuring_doubl_1\/","title":{"rendered":"Measuring Double Stars &#8211; Page 1 of 3"},"content":{"rendered":"<p>A few months ago, I invested in a Meade 12 mm Astrometric Eyepiece that I could use in measuring double stars. I calibrated the eyepiece scale in June, and have used a few times since them. I&#8217;m definitely at the novice stage of using this eyepiece to measure doubles, but I wanted to pull together a tutorial describing the process I&#8217;ve used so far. I based most of this on the article &#8220;Observing Double Stars for Fun and Science&#8221; by Ronald Charles Tanguay in the February 1999 issue of <i>Sky and Telescope<\/i>. Tanguay&#8217;s article recommends calibrating the position angle circle at the beginning of an observing session and using that throughout the session. Because I&#8217;m using a Newtonian telescope and need to adjust the position of the OTA in the tube rings as I move to different portions of the sky, I wouldn&#8217;t be able to retain that calibration from one double to the next. So the method I describe calibrates the PA ring for each double observed.<\/p>\n<p>As I use this process to measure more doubles, I&#8217;ll be comparing my values to WDS values along the way to see whether I&#8217;m getting better with measurement accuracy. According to Tanguay, measurements of stars separated by about 1 arc second should vary no more than +\/- 10% for separation and +\/- 5 degrees for PA. For widely separated stars in the vicinity of 100 arc seconds, separation should vary no more than +\/- 1% and PA by no more than +\/- .5 degrees. Any suggestions for improvement in the method I&#8217;m using are appreciated.<\/p>\n<h3>Constructing the Astrometric Eyepiece PA Scale<\/h3>\n<p><b>Materials Used:<\/b><\/p>\n<ul>\n<li>Astrometric Eyepiece<\/li>\n<li>Barlow<\/li>\n<li>360 Degree Protractor<\/li>\n<li>Small piece of foam core board<\/li>\n<li>Strip of mylar\/transparency film<\/li>\n<li>Pen knife\/Xacto knife<\/li>\n<li>Tape<\/li>\n<li>Fine tip permanent marker<\/li>\n<\/ul>\n<p>1) If the protractor has a central brace, cut most of it out leaving just the outside plastic circle intact. <\/p>\n<p style=\"text-align: center\"><img decoding=\"async\" src=\"http:\/\/www.perezmedia.net\/beltofvenus\/archives\/images\/2008\/img2008013001_DSM_Step01.jpg\"><\/p>\n<p style=\"text-align: center\"><img decoding=\"async\" src=\"http:\/\/www.perezmedia.net\/beltofvenus\/archives\/images\/2008\/img2008013001_DSM_Step02.jpg\"><\/p>\n<p>2) Tape this circular protractor to a sheet of foam core and then trim off the outside edge of foam core material. <\/p>\n<p style=\"text-align: center\"><img decoding=\"async\" src=\"http:\/\/www.perezmedia.net\/beltofvenus\/archives\/images\/2008\/img2008013001_DSM_Step03.jpg\"><\/p>\n<p style=\"text-align: center\"><img decoding=\"async\" src=\"http:\/\/www.perezmedia.net\/beltofvenus\/archives\/images\/2008\/img2008013001_DSM_Step04.jpg\"><\/p>\n<p>3) Using the 0\/90\/180\/270 degree positions on the protractor, carefully draw bisecting lines at right angles across the foam core to mark the center of the disc. <\/p>\n<p style=\"text-align: center\"><img decoding=\"async\" src=\"http:\/\/www.perezmedia.net\/beltofvenus\/archives\/images\/2008\/img2008013001_DSM_Step05.jpg\"><\/p>\n<p>4) Measure the outside diameter of your barlow just below the locking screw (hopefully it is the same diameter as the top of the barlow, since this will make measuring easier). <\/p>\n<p>5) Subtract 1-2 mm from this diameter (for a snug fit) and use a circle template or compass to draw a circle centered on the mark you made in step 3.<\/p>\n<p style=\"text-align: center\"><img decoding=\"async\" src=\"http:\/\/www.perezmedia.net\/beltofvenus\/archives\/images\/2008\/img2008013001_DSM_Step06.jpg\"><\/p>\n<p>6) Use a pen knife\/Xacto knife to cut a hole in the disc where you marked the circle in step 5.<\/p>\n<p style=\"text-align: center\"><img decoding=\"async\" src=\"http:\/\/www.perezmedia.net\/beltofvenus\/archives\/images\/2008\/img2008013001_DSM_Step07.jpg\"><\/p>\n<p style=\"text-align: center\">&#8212; <a href=\"http:\/\/www.perezmedia.net\/beltofvenus\/archives\/000777.html\">PAGE 2 OF 3<\/a> || <a href=\"http:\/\/www.perezmedia.net\/beltofvenus\/archives\/000776.html\">PAGE 3 OF 3<\/a> &#8212;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Measuring Double Stars &#8211; Page 1 of 3<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[64,56,39],"tags":[],"class_list":["post-394","post","type-post","status-publish","format-standard","hentry","category-article","category-double-star","category-tools-and-techniques"],"jetpack_featured_media_url":"","jetpack-related-posts":[{"id":392,"url":"https:\/\/perezmedia.net\/beltofvenus\/2008\/01\/28\/my_method_for_m\/","url_meta":{"origin":394,"position":0},"title":"Measuring Double Stars &#8211; Page 3 of 3","author":"jperez1690","date":"January 28, 2008","format":false,"excerpt":"Measuring Double Stars - Page 3 of 3","rel":"","context":"In &quot;Article&quot;","block_context":{"text":"Article","link":"https:\/\/perezmedia.net\/beltofvenus\/category\/article\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":393,"url":"https:\/\/perezmedia.net\/beltofvenus\/2008\/01\/30\/measuring_doubl\/","url_meta":{"origin":394,"position":1},"title":"Measuring Double Stars &#8211; Page 2 of 3","author":"jperez1690","date":"January 30, 2008","format":false,"excerpt":"Measuring Double Stars - Page 2 of 3","rel":"","context":"In &quot;Article&quot;","block_context":{"text":"Article","link":"https:\/\/perezmedia.net\/beltofvenus\/category\/article\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":27,"url":"https:\/\/perezmedia.net\/beltofvenus\/2004\/08\/24\/observing_repor_1\/","url_meta":{"origin":394,"position":2},"title":"Observing Report &#8211; 08.24.2004","author":"jperez1690","date":"August 24, 2004","format":false,"excerpt":"20040824_01","rel":"","context":"In &quot;Astro Photography&quot;","block_context":{"text":"Astro Photography","link":"https:\/\/perezmedia.net\/beltofvenus\/category\/astro-photography\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":404,"url":"https:\/\/perezmedia.net\/beltofvenus\/2008\/05\/01\/v_hydrae_burnha\/","url_meta":{"origin":394,"position":3},"title":"V Hydrae (Burnham 1428)","author":"jperez1690","date":"May 1, 2008","format":false,"excerpt":"V Hydrae (Burnham 1428)","rel":"","context":"In &quot;Double Star&quot;","block_context":{"text":"Double Star","link":"https:\/\/perezmedia.net\/beltofvenus\/category\/double-star\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":263,"url":"https:\/\/perezmedia.net\/beltofvenus\/2006\/08\/17\/double_star_ske_5\/","url_meta":{"origin":394,"position":4},"title":"Double Star Sketching and Digitizing &#8211; Page 1 of 4","author":"jperez1690","date":"August 17, 2006","format":false,"excerpt":"Double Star Sketching and Digitizing - Page 1","rel":"","context":"In &quot;Double Star&quot;","block_context":{"text":"Double Star","link":"https:\/\/perezmedia.net\/beltofvenus\/category\/double-star\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":37,"url":"https:\/\/perezmedia.net\/beltofvenus\/2004\/10\/04\/m71\/","url_meta":{"origin":394,"position":5},"title":"Messier 71","author":"jperez1690","date":"October 4, 2004","format":false,"excerpt":"M071","rel":"","context":"In &quot;Deep Sky&quot;","block_context":{"text":"Deep Sky","link":"https:\/\/perezmedia.net\/beltofvenus\/category\/deep-sky\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]}],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/perezmedia.net\/beltofvenus\/wp-json\/wp\/v2\/posts\/394","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/perezmedia.net\/beltofvenus\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/perezmedia.net\/beltofvenus\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/perezmedia.net\/beltofvenus\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/perezmedia.net\/beltofvenus\/wp-json\/wp\/v2\/comments?post=394"}],"version-history":[{"count":0,"href":"https:\/\/perezmedia.net\/beltofvenus\/wp-json\/wp\/v2\/posts\/394\/revisions"}],"wp:attachment":[{"href":"https:\/\/perezmedia.net\/beltofvenus\/wp-json\/wp\/v2\/media?parent=394"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/perezmedia.net\/beltofvenus\/wp-json\/wp\/v2\/categories?post=394"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/perezmedia.net\/beltofvenus\/wp-json\/wp\/v2\/tags?post=394"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}