{"id":210,"date":"2013-03-03T23:04:15","date_gmt":"2013-03-03T22:04:15","guid":{"rendered":"http:\/\/honza.paws.cz\/?p=210"},"modified":"2013-03-03T23:29:15","modified_gmt":"2013-03-03T22:29:15","slug":"ameterska-astronomicka-fotografie","status":"publish","type":"post","link":"http:\/\/honza.paws.cz\/?p=210","title":{"rendered":"Amet\u00e9rsk\u00e1 astronomick\u00e1 fotografie"},"content":{"rendered":"

Nem\u00e1m k dispozici typickou v\u00fdbavu pro astrofotografii, jen b\u011b\u017enou zrcadlovku Pentax K-r, objektiv Sigma 70-300\u00a0mm a stativ. Nem\u00e1m je\u0161t\u011b ani paralaktick\u00fd stolek, i kdy\u017e ho m\u00e1m v pl\u00e1nu postavit. V p\u0159\u00edpad\u011b, \u017ee objektiv nesleduje zd\u00e1nliv\u00fd pohyb hv\u011bzd po nebesk\u00e9 sf\u00e9\u0159e, je nutno volit \u010das trv\u00e1n\u00ed expozice \u00fam\u011brn\u00fd ohniskov\u00e9 d\u00e9lce, tak aby se pohyb obrazu hv\u011bzdy po sn\u00edma\u010di v pr\u016fb\u011bhu expozice minimalizoval. Na www.astro-forum.cz<\/a> jsem se dozv\u011bd\u011bl nejeden detail. Z\u0159ejm\u011b nejlep\u0161\u00ed je samotn\u00e1 fotografie<\/a>. Dozv\u00edte se, \u017ee m\u00e1te pou\u017e\u00edt \u010das 0,8 s, a ISO6400 p\u0159i 300 mm ohnisku. Nejlep\u0161\u00ed je, m\u00e1te-li k fotoapar\u00e1tu d\u00e1lkov\u00e9 ovl\u00e1d\u00e1n\u00ed, nemus\u00edte pak vyhazovat prvn\u00ed rozmazan\u00fd sn\u00edmek a samoz\u0159ejm\u011b intervalovou expozici. \u010c\u00edm v\u00edc sn\u00edmk\u016f t\u00edm l\u00e9pe. Ale samotn\u00e9 focen\u00ed nen\u00ed legrace, za\u010d\u00edn\u00e1 u\u017e dlouhou dobu p\u0159ed prvn\u00edm stisknut\u00edm spou\u0161t\u011b v\u00fdrobou Bahtinovy masky. Bez v\u00edce \u010di m\u00e9n\u011b p\u0159esn\u00e9ho zaost\u0159en\u00ed budou sn\u00edmky k ni\u010demu. D\u00e1le: objekt by m\u011bl b\u00fdt na obloze co nejv\u00fd\u0161e, kv\u016fli ten\u010d\u00ed vrstv\u011b plynu, kterou mus\u00ed sv\u011btlo a\u017e k objektivu urazit. To je n\u011bkdy v protikladu s t\u00edm, \u017ee objektiv zaj\u00ed\u017ed\u00ed dovnit\u0159 pouzdra, je-li nam\u00ed\u0159en vzh\u016fru. Je t\u0159eba jej zajistit gumi\u010dkou, \u010di podobn\u011b. Na stanovi\u0161ti s co nejmen\u0161\u00edm sv\u011bteln\u00fdm zne\u010di\u0161t\u011bn\u00edm je nutno nejprve vyhledat objekt a n\u011bkolika sn\u00edmky, \u010di pomoc\u00ed LiveView zaost\u0159it za p\u0159isp\u011bn\u00ed Bahtinovy masky. Jsme-li p\u0159ipraveni rozvrhneme po\u010det a druh sn\u00edmk\u016f. Ty jsou pro za\u010d\u00e1tek \u010dty\u0159i: light (b\u011b\u017en\u00fd sn\u00edmek hv\u011bzd), dark, flat a bias. Light sn\u00edmk\u016f po\u0159\u00edd\u00edme co nejv\u00edce t\u0159eba ne\u017e objekt opust\u00ed zorn\u00e9 pole, pak m\u016f\u017ee dle na\u0161\u00ed libosti n\u00e1sledovat po\u0159\u00edzen\u00ed dark a bias sn\u00edmk\u016f a znovu nap\u0159\u00edklad n\u011bkolik light. Temn\u00e9 jsou foceny stejn\u00fdm nastaven\u00edm jako ty barevn\u00e9, jen s krytkou na objektivu, jde o to z\u00edskat obraz \u0161umu produkovan\u00e9ho samotn\u00fdm sn\u00edma\u010dem, ten se pak p\u0159i zpracov\u00e1n\u00ed ode\u010d\u00edt\u00e1 od light sn\u00edmk\u016f, aby byly \u0161umu zbaveny. Bias je focen na stejn\u00e9 nastaven\u00ed jako dark s v\u00fdjimkou \u010dasu, kter\u00fd se nastav\u00ed na nejkrat\u0161\u00ed mo\u017en\u00fd a objektiv je st\u00e1le zakryt\u00fd. Tyto sn\u00edmky po\u0159izujeme b\u011bhem focen\u00ed za stejn\u00fdch podm\u00ednek jako barevn\u00e9, projevuje se toti\u017e okoln\u00ed teplota apod. Flat si po\u0159izuji s pomoc\u00ed monitoru po\u010d\u00edta\u010de a eurofoli\u00ed, kter\u00e9 b\u00edl\u00e9 sv\u011btlo z monitoru (za p\u0159edpokladu, \u017ee cel\u00e1 obrazovka bude b\u00edl\u00e1) rovnom\u011brn\u011b rozpt\u00fdl\u00ed. Tento sn\u00edmek m\u00e1 kompenzovat vliv optick\u00e9 soustavy a proto je d\u016fle\u017eit\u00e9, aby soustava byla ve stejn\u00e9 poloze jako p\u0159i focen\u00ed barevn\u00fdch sn\u00edmk\u016f.<\/p>\n

Sn\u00edmky se nechaj\u00ed automaticky zpracovat programem DeepSkyStacker a v\u00fdsledek m\u016f\u017ee vypadat i l\u00e9pe ne\u017e tento m\u016fj: \"M42\"<\/p>\n","protected":false},"excerpt":{"rendered":"

Nem\u00e1m k dispozici typickou v\u00fdbavu pro astrofotografii, jen b\u011b\u017enou zrcadlovku Pentax K-r, objektiv Sigma 70-300\u00a0mm a stativ. Nem\u00e1m je\u0161t\u011b ani paralaktick\u00fd stolek, i kdy\u017e ho m\u00e1m v pl\u00e1nu postavit. V p\u0159\u00edpad\u011b, \u017ee objektiv nesleduje zd\u00e1nliv\u00fd pohyb hv\u011bzd po nebesk\u00e9 sf\u00e9\u0159e, je nutno volit \u010das trv\u00e1n\u00ed expozice \u00fam\u011brn\u00fd ohniskov\u00e9 d\u00e9lce, tak aby se pohyb obrazu hv\u011bzdy […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"http:\/\/honza.paws.cz\/index.php?rest_route=\/wp\/v2\/posts\/210"}],"collection":[{"href":"http:\/\/honza.paws.cz\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/honza.paws.cz\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/honza.paws.cz\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/honza.paws.cz\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=210"}],"version-history":[{"count":11,"href":"http:\/\/honza.paws.cz\/index.php?rest_route=\/wp\/v2\/posts\/210\/revisions"}],"predecessor-version":[{"id":219,"href":"http:\/\/honza.paws.cz\/index.php?rest_route=\/wp\/v2\/posts\/210\/revisions\/219"}],"wp:attachment":[{"href":"http:\/\/honza.paws.cz\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=210"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/honza.paws.cz\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=210"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/honza.paws.cz\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=210"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}