www.astrocafe.hk

連續幾日試影，但太多雲(和晚霞)無功而回。

難得上星期六黃昏能見度高及極少晚霞，設影一下。

http://www.raymondtse-lawyer.com/astro/ ... upiter.htm

Raymond Tse

開始對鏡頭多留意，以便日後用在自動化拍攝設備上，你是用什麼鏡頭的？

水星與木星相距不足8度，原打算用FD300F2.8+5DII 用直倒拍攝。
但要攞多一點地景，最後用70-200+5DII，弹性高。
拍的一幅用93mmF4，2.5秒曝光。

thanks for the info.

我暫時的西藏趟頂房以廣角鏡為主，好處是焦準比較容易控制：

viewtopic.php?f=12&t=1188&start=320

但180以上的，我還是選Borg，始終比鏡頭銳些及穏定些：

viewtopic.php?f=17&t=1759

經過一年多的實操，+10至-10度的焦準約相差0.2mm，所以我只需6月及12月各找一個晚上，請站上人員幫我手調一次便可以，昨晚才做了一次，請站上助手每調0.025mm我便拍一張及用遠端桌面檢視星點銳利度，最後發現年多以來的冷暖週期所調出來的焦準很一致。當然這鏡跟高端APO還是有些分別，特別在色球差方面，所以若拍攝期間(例如維時數天)温差有+/-5度以上，我也不會調，實質影響不大。

Agreed that any focal length above 200-300 should be left to telescope instead of lens.

But camera lens still has its advantage : fast F-ratio (any wide angle lens is fast at F1.4 to F2.8)
and sometimes large aperture (eg EF200F2, FD300 F2.8 etc).

I am now in the process of using FD300F2.8 modified to couple with small pixel CCD (and filter wheel) to do
wide to medium (true FOV about 2.0x2.5 degree) deepsky.

As for focusing, Robofocus automatic focusing would be used for fully robotic operation and
to do away with manual adjustment. I even use it for focusing my electronic finder (EF135+ST402) on
top of TEC140F7+Atik314L.

My new setup of FD300 with SX Filter Wheel and 490EX CCD would be found in
the Observatory webpage at (at the middle row Telescopes/Lens) :
http://www.raymondtse-lawyer.com/astro/ ... atory.html

Raymond Tse

Raymond TSE 寫:Agreed that any focal length above 200-300 should be left to telescope instead of lens.

But camera lens still has its advantage : fast F-ratio (any wide angle lens is fast at F1.4 to F2.8)
and sometimes large aperture (eg EF200F2, FD300 F2.8 etc).

I am now in the process of using FD300F2.8 modified to couple with small pixel CCD (and filter wheel) to do
wide to medium (true FOV about 2.0x2.5 degree) deepsky.

始終以我有限經驗，鏡頭在天文上的用途，無論照明度、良像圈，都不可盡用其最大光圈，收細一到兩級才成，另外我想焦準在温度下的變化也很複雜?

某程度上，以我的環境來說，除非拍彗星，大多數情況不用太爭分奪秒，f4是一個很合適的光圈，f3是下限，突破這下限，要付出不少代價去妥協。

Raymond TSE 寫:As for focusing, Robofocus automatic focusing would be used for fully robotic operation and
to do away with manual adjustment. I even use it for focusing my electronic finder (EF135+ST402) on
top of TEC140F7+Atik314L.

我那次自行改裝，用到Canon 180 f3.5 Macro上的經驗很差，最後還是要用人手輔助，或許買成品回來裝會好些...

viewtopic.php?f=16&t=549
viewtopic.php?f=29&t=490
viewtopic.php?f=29&t=507

Raymond TSE 寫:My new setup of FD300 with SX Filter Wheel and 490EX CCD would be found in
the Observatory webpage at (at the middle row Telescopes/Lens) :
http://www.raymondtse-lawyer.com/astro/ ... atory.html

Raymond Tse

很有用的參考，謝!