Part 2. 器材概述
PENTAX的高階定位相機中,全片幅的K-1和K-1 ii,以及APS-C片幅的K-3 ii有內建GPS系統,其他型號則需要添購O-GPS1(小小一個幾十克重左右吧)裝在熱靴上方可使用GPS。使用的時候要在主選單中開啟天體追蹤,開啟GPS開關,定位並校正(初次使用需兩分鐘左右,成功定位過之後每次重開校正完大概只需要半分鐘)。轉盤轉至B快門模式,再透過按一下小綠按鈕來切換天體追蹤或者一般B快門模式即可。 相機本身會依照所使用的焦段來限制單次曝光時間,譬如55-300mm這顆APS-C鏡頭裝在K-1 ii上面拉到300mm時,系統強制最多可曝50秒。相較於它廠相機只能曝一兩秒,PENTAX內建的天體追蹤讓星野攝影的方便性有飛躍的提升。 -- 你用過超廣角鏡拍星系嗎XD Among high-end models of PENTAX, only K-1, K-1 ii, (FF) and K-3 ii (APS-C) are equipped with GPS. Other models should be paired with a small accessory called O-GPS1 mounted on the hot shoe. After turn on the GPS and astrotracer and calibrate, one can enjoy tracking stars. Don’t forget to press the green bottom to shift B mode to astrotracer mode. The camera will limit the maximal length of exposure according to the focal length. For example, a camera without astrotracer mounted with a 300 mm lens can go without star streaks in 1-2 seconds, but PENTAX makes it possible to shoot for up to 50 seconds in a single shot. For wide angle lenses, the limitation is up to 5 minutes. Now you can happily live without an equatorial mount, LOL. Have you ever shoot galaxies with an ultra-wide lens? XD Part 1. 前言
天文攝影有所謂的「600法則」,可以換算在135片幅下,各焦段可以曝幾秒鐘而不致星點拖尾變成星軌。舉例來說,300mm的全片幅鏡頭,600/300=2,一次曝光兩秒鐘,星點仍大致可以是漂亮的圓形,再久就不圓甚至會拖出星軌。同樣的道理,使用20mm的超廣角鏡頭時,600/20=30,一曝三十秒也是可以接受的。 |