7月尾澳洲Ayers Rock之旅

[PaulNg]

7月尾和25個學生到澳洲東南部考察地理及到中部觀星。由於只得3 晚的觀測時間, 拍攝還是掃射式。但天空質素實在好, 所以照片還可以。

好像發錯了主題...

無論如何, 先上傳一些環境照:

[社長]

謝謝分享，我本來今年七月也會帶一批學生到澳洲拍攝，最後因為旅行社問題改往台灣。

請教一下澳洲當地哪間旅館可能適合接待廿多位師生及就地攝星的? 當然是要晴天率合理為先。

以我個人計，若到澳洲拍的話，會集中在南天極直徑80度範圍的天體，因為南天極60度直徑是我在西藏看不到的，而西藏10度以上已可以拍到一些東西，所以以優先次序來說，把那80度內首要的10個8個天體拍下，或許已完了我的南天拍攝計劃。

當然有了以前的打游擊經驗，我會用f4光圈或更大的去拍，以提升效率。所以目前先優化一下手上的RH200，也不排除把那台Borg 60ED帶過去，是245mm f4.1光圈的。

[PaulNg]

那個叫Desert Gardens Hotel. 很大的地區, 有超市商店游泳池之類.

對我來說要是天空質素好, 什麼緯度都可以拍不停，實在太少外出的機會。就算常拍的天區一玩mosaic就可以沒完沒了，

[社長]

當然，我的情況跟你有些不同，有了西藏，我不會拍西藏可以拍到的天區，跟自己過不去，因為現在我已受不了為一個目標投入二三十小時以上又LRGBHSO等通道去捱夜，但那又近乎高質照片的下限。

所以去南半球純粹是圓個心願，也不會常去。或許把深空交給自動化天文台後，我還是應投入多點在行星月面上。

請教一下，那地區會不會有什麼light dome或其他本地性的問題?

[PaulNg]

什麼問題都沒有, 唯一的是太遠. 除非乘飛機進去, 否則駕車要數天。另外則是物價, 如食物生活用問比出面都貴。
現在香港想轉型長焦或窄頻拍攝, 國外的搖控投入的金錢時間真的付擔不起....

[社長]

我很同意在香港拍窄頻有很大發揮空間，不少在市中心拍的，跟在高清天空下比較，差距沒有想像中大。

但那些星系則別無他法只能"遠走高飛"了。

[willis]

Paul,
It seemed that u brought lots of instrument to Australia. From the photos, there were 3 mounts! I learned from hkastroforum, that u got problem with 125SD & 7870. Have u adjusted the 7870 for full frame? It affects a lot at the corner performance. I guess if u tune it probably, not only the double-fan shape diffraction will be improved, but the chromatic aberration. I encountered similar situation when I tried to match 7870 with APM 80/480.
Regards,
Willis

[社長]

我的Borg 60ED配7870亦有類似情況，甚至有些許色球差的問題，竹尸竹一，相比我用過的Canon 180 Macro或Nikon 200 Macro相機鏡頭像質明顯好得多，但始終跟Triplet APO + 2片式平場鏡或3片式減焦鏡是有點差距。

[willis]

According to Borg's website, the 7870 should be set to 640mm instead of 750mm for 125SD.
http://www.sciencecenter.net/hutech/pri ... l/7870.htm

[PaulNg]

Paul,
It seemed that u brought lots of instrument to Australia. From the photos, there were 3 mounts! I learned from hkastroforum, that u got problem with 125SD & 7870. Have u adjusted the 7870 for full frame? It affects a lot at the corner performance. I guess if u tune it probably, not only the double-fan shape diffraction will be improved, but the chromatic aberration. I encountered similar situation when I tried to match 7870 with APM 80/480.
Regards,
Willis

Just 2 EM11, and one toast pro. There were a lot of students, so there were many who could help.

I did set the reducer to 640mm, but i did not read "need to set inward 4mm for FF sensors" that part.

我的Borg 60ED配7870亦有類似情況，甚至有些許色球差的問題，竹尸竹一，相比我用過的Canon 180 Macro或Nikon 200 Macro相機鏡頭像質明顯好得多，但始終跟Triplet APO + 2片式平場鏡或3片式減焦鏡是有點差距。

Though doublet, it is very difficult to have a 5" APO with such an airline portable weight. It is even lighter than many 4" triplet APOs. I talked to Ted in Hutech through email right after i finished processing the photos, he said the diffraction would still be there even the 4mm was adjusted. It is due to the small aperture of the reducer.

[PaulNg]

既然係咁出張比家睇:

IC4592 (The Blue Horsehead)

Optics: Borg 125SD, 7870 0.7x reducer
Mount: Takahashhi EM11
Camera: Canon EOS 6D modified, ISO800
Exposure: 30x300sec (2.5 hrs)
Guiding: Lodestar, 50/200 guidescope, PHD (dithering enabled)
Softwares: Photoshop, DSS, Pixinsight, BackyardEOS

[社長]

既然係咁出張比家睇:

IC4592 (The Blue Horsehead)

Optics: Borg 125SD, 7870 0.7x reducer
Mount: Takahashhi EM11
Camera: Canon EOS 6D modified, ISO800
Exposure: 30x300sec (2.5 hrs)
Guiding: Lodestar, 50/200 guidescope, PHD (dithering enabled)
Softwares: Photoshop, DSS, Pixinsight, BackyardEOS

這馬頭我也有拍，陰差陽錯，西藏拍攝時總遇到些問題，至今沒處理好　

用這類Borg鏡拍的照片可以很有美感，但不可細看，至少不太適合100%出圖。

用它拍RGB然後跟冷凍相機的L合成還可以，但單靠這鏡本身是打了點折扣的。

viewtopic.php?f=17&t=3604#p22830

看到你使用的軟件有點好奇，請教一下，為何不單靠MaximDL拍攝(有Dithering)，然後用PixInsight處理便算?

P.S., 論Dithering我較喜歡TheSky用的spiral dithering，MaximDL只有Random的不太好。

[willis]

The double-fan diffraction and CA were outside the APSC region. This was exactly what I encounter before. After fine tuning for full frame, moving it "about 4mm" further, both double fan & CA will be improved. In my case, matching 7870 and APM 80/480, the stars at corners are not perfect. However, the result is acceptable. Maybe Borg reducer works perfectly with Borg objectives.

[社長]

The double-fan diffraction and CA were outside the APSC region. This was exactly what I encounter before. After fine tuning for full frame, moving it "about 4mm" further, both double fan & CA will be improved. In my case, matching 7870 and APM 80/480, the stars at corners are not perfect. However, the result is acceptable. Maybe Borg reducer works perfectly with Borg objectives.

情況不只這樣，是星點有一定光暈的，尤其是光譜藍端，所以我說拍單反講求整體美感可以，或以單反做彩色通道，跟其他鏡配冷凍相機的L通道合成還可以，單靠自己100%出圖不太成。

就算我的Borg 60ED配7870，合成f4.1也是這樣。

單平場不減焦應會好些，但我未測試過。

[PaulNg]

The double-fan diffraction and CA were outside the APSC region. This was exactly what I encounter before. After fine tuning for full frame, moving it "about 4mm" further, both double fan & CA will be improved. In my case, matching 7870 and APM 80/480, the stars at corners are not perfect. However, the result is acceptable. Maybe Borg reducer works perfectly with Borg objectives.

I'm glad to hear that. I'll do further adjustments to test it out. I can live with FSQ-ish diffraction gaps, but this is too much.

情況不只這樣，是星點有一定光暈的，尤其是光譜藍端，所以我說拍單反講求整體美感可以，或以單反做彩色通道，跟其他鏡配冷凍相機的L通道合成還可以，單靠自己100%出圖不太成。

就算我的Borg 60ED配7870，合成f4.1也是這樣。

單平場不減焦應會好些，但我未測試過。

小量藍／紫光暈不是太大問題, 在我的照片中這樣的光暈還是可以接受的. 我另外配了一個2.5"的flattener, 試拍過一次沒有這樣的問題，所以我相信是7870的設計不太好。我其實非常希望可以有一個高質的減焦平場鏡匹配125SD，不知道給triplet用的Riccardi 0.75X可不可行。

[PaulNg]

繼續出相:

天蠍頭及中心
Canon 5Dii modified, iso1600, 24-70ii (70mm f/4)
Exposure 3min x 30
Toast-pro

[PaulNg]

用球頭做不到精確構圖及相機角度旋轉，所以做成這兩張mosaic失敗的作品.

Milkyway Centre and Sagittarius
Canon 24-70mm F/2.8 Lii (70mm f/4)
Canon EOS 5D Mark II, ISO1600, 3min x 25
TOAST Pro

[PaulNg]

看到你使用的軟件有點好奇，請教一下，為何不單靠MaximDL拍攝(有Dithering)，然後用PixInsight處理便算?

P.S., 論Dithering我較喜歡TheSky用的spiral dithering，MaximDL只有Random的不太好。

我沒有買MaximDL, 可能在玩單色CCD的時候才用。
本身用PHD 做guiding， 可以和BackyardEOS做溝通自動化dithering.
以上的程式就是BYEOS要買而已, 並且相當好用。

[社長]

用球頭做不到精確構圖及相機角度旋轉

我到過澳洲出席天文館會議，但未試過在當地拍攝。

有點懷疑拍廣角銀河，或多或少到這面貎已差不多? 感覺在不同地點，天空質量好的話，拍到這深度也某程度上到頭了?

P.S., 亦是同樣原因，我一直避免用球頭，寧可用一片鋁角去解決橫直倒的問題。

[社長]

看到你使用的軟件有點好奇，請教一下，為何不單靠MaximDL拍攝(有Dithering)，然後用PixInsight處理便算?

P.S., 論Dithering我較喜歡TheSky用的spiral dithering，MaximDL只有Random的不太好。

我沒有買MaximDL, 可能在玩單色CCD的時候才用。
本身用PHD 做guiding， 可以和BackyardEOS做溝通自動化dithering.
以上的程式就是BYEOS要買而已, 並且相當好用。

明白了。

我當時也花了好像5000多元買MaximDL，ACP Observatory更貴。

若非要兩者配合搞自動化，我寧可用The Sky。

未試過Backyard EOS，或許有機會到南半球拍攝時要試試，因為若非搞自動化我根本不想用MaximDL。