[Philos]

因為z5 最長曝光得4 秒..........

[Philos]

有無z5 用家回應一下我........謝

[winkkonglee]

i see

[Rol]

If long time expo just 4 sec. can only shoot Venus at evening or sunset.

other star is too dark to catch by 4 sec.

[cpinfo]

好難﹐ 得4秒﹐ 影暗小小夜景都嫌唔夠。

[窮書生]

唔知太陽算唔算星星呢?

[kunyu]

影星星唔係部機快門時間長或者有B 門就影到,重要有導星儀先得,否則只係影到一條條線咁o架渣...

[Rol]

影星星唔係部機快門時間長或者有B 門就影到,重要有導星儀先得,否則只係影到一條條線咁o架渣...
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Need to have "Equatorial Mount" (赤道儀) on tripod. The "Equatorial Mount" (赤道儀) is different from normal tripod of taking
photo, it has axis which should point exactly North and at height of angle 22.5 degree (same as Hong Kong latitude). Then the
turning of DC / Telescope on "Equatorial Mount" can be circular and same way like the star in the sky.

To keep the DC with same moving pace as the star, also need the help of telescope. The telescope and DC is putting side by side on "Equatorial Mount". The telescope is pointing to the star and you need to manually fine tune the star is within the sight of telescope and so the DC is moving at same pace as the star in the sky. The more convenient way is to connect the tracking motor with "Equatorial Mount" and it can automatic tracking the star. In above way, long time exposure of 10-20 min can have very brilliant cosmos photo.

Place of taking star photo is another question, all city area of Hong Kong is not suitable for taking star photo, The city light is reflecting red on sky and DC will absorb such red light in long time exposure. Now only Sai Kung and countryside island can take complete dark star sky.

Z5 or any DC are definitely unable to fulfill above job, not mention DC without "B" long time exposure. Just 10 min long time exposure in DC already generate many noise bright point which would mix up with the star, then you are shooting noise point rather than star. Now in market only Canon 20 DA is specially design for star shooting.

[oldfield]

如果你指映天文相, 答案係可以, 但呢部機完全唔理想.

映月球 afocal, 唔夠 webcam 好, 映太陽無論映 h-alpha 同 white light 都係唔夠 webcam 好. 映 afocal 整體黎講, 因為個 lens 太大, 好難夾 eyepiece, 我發現 vignetting 極嚴重.

zoom 盡映月球都可以, 但呢個 lens zoom 盡唔 sharp.

映 deep sky 得 4s, 可以話乜都映唔倒, 不過用得 DC 仔都好難映得好 deep sky.

如果映下金星合月, 火星合月之類就算係唔錯, 早前水星同金星幾近果陣, 雖然水星唔算光, 但都映倒... 早幾個月木星合月, 手持都仲得... !!!

另外, 有個另類用途, 我用個 52mm filter 加塊 baader film, 用黎 detect 有無大太陽黑子, 都幾有效, 發現如果有大野先 set 鏡再用 webcam 映, 呢個用途都幾好架.

不過如果純以天文出發, 呢部機可以唔使諗咯... :-)

[Gowest]

買部靚少少幾百蚊既web cam咪得囉,鍾意曝幾耐光都得。

[oldfield]

webcam 要改先可以長時間曝光, 而且效果唔太好, 因為粒 chip 太細, 只可以映細既 deep sky objects, 仲要加 peltier 減 noise...

我有一張用 z5 映既 h-alpha 太陽, 可以參考下...

http://gallery.hkas.org.hk/displayimage.php?album=9&pos=6

[winkkonglee]

Canon 20Da could take "stars" pictures!