鏡神 測試自製14吋牛頓鏡報告 --- 2

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Wongsir
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註冊時間: 週六 28 6月, 2003 12:03
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鏡神 測試自製14吋牛頓鏡報告 --- 2

文章 Wongsir » 週三 26 11月, 2003 21:05

剛剛收到陳玉驎兄寄給我的試鏡報告,
現全文收錄如下:


Dear sky lovers,

On 20th Nov when the Hong Kong Observatory announced that a cold front will arrive at Hong Kong I did look forward for a very transparent sky for deep sky viewing. I prepared the 14 inch Newtonian, clean all eyepieces and prepared a list of object I would target on in case of good weather.

Experience told me that shortly before the arrival of the cold front there was always a brief moment of very transparent sky available for deep sky hopping or photography. Finally at 21st Nov the sky suddenly turned clear, there was an unusual sunshine prevailing for all day and I knew that this is the right moment. When my friend asked me if I was interested for a trip to Water Mouth that night my answer was an immediate yes.

We arrived late to the site and not until 1945 hrs did I completely finish setting up the 14 inch Newtonian. When I look up onto the sky it was transparent and clear, which was rarely encountered in Hong Kong but was as expected. The Andromeda galaxy M31 turned into an easy naked eye object. The summer milky way was so obvious although it was low on the western sky. No clouds and, stunning as I was at that moment, no other parties came for deep sky imaging or star seeing, except me and my friends and Raymond Tse, who was discovered walking with his equipment along the road alone and picked up by our taxi.

I immediately turned the 14 inch to some famous DDSO ( dim deep sky objects ) to test the sky condition :-

1. M33 – easily seen with the 14 inch. Nucleus and spiral arm were obviously identified. The nebula inside the spiral arm, NGC 604, was also very clearly seen. Imagine how stunning it was when you discovered that you were just looking onto a nebula more than 3 million light years away inside another galaxy.

2. NGC 253 – this giant galaxy was difficult to see in Hong Kong due to its low altitude and surface brightness. This was not the case tonight, one could feel how giant it was as it filled up the whole apparent field of the super wide 24.5 mm eyepiece ( at 70 X ). Averted vision showed the central bulge filled with dark filaments. The neighboring globular NGC288 could also been seen without difficulty.

3. The Helix nebula – This nebula is notorious among deep sky viewers for its extremely low surface brightness. To directly see it inside an eyepiece required sky of very good darkness and transparency. Hence you could imagine how surprising it was as the Helix jumped out from the view of the eyepiece as we pointed the telescope to the right place. Inside the eyepiece the Helix appeared to be a circular patch of light about the size of the moon. We did not see the helix shape nor any 「hole」 inside the big patch of light. However averted vision showed some dark filament evolving out from the central of the nebula.

There was no doubt that the sky was unusually transparent that night. As commented by my friend Mr. HL Chung, a well experienced deep sky observer, 「 This is a night of miracle, I cannot believe I can see the Helix in Hong Kong, especially nowadays.」 This was a very good description on how we feel that night.

The clear sky lasted for about 3 hours as clouds started to fill up the sky at about 2300 hrs. Merciless cold breeze attacking on our bodies told that it was about time to end up. To my surprise there was no other parties come for sky shooting during this whole favorable session. Were they too busy or too lazy ? Or just that they were afraid of clouds appearing at any moment?

Anyway if it happened that somebody came at the right moment and make some good deep sky photography, he surely win through with big catches.

Best regards

Chan Yuk Lun
22-11-2003
最後由 Wongsir 於 週五 28 11月, 2003 09:17 編輯,總共編輯了 2 次。

oldsaltfish
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文章 oldsaltfish » 週四 27 11月, 2003 09:21

不錯,冷空氣一來,透明度就會很好,
這個有利條件,在北方還是比較多的。

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david_kmng
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註冊時間: 週五 11 7月, 2003 00:10
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文章 david_kmng » 週四 27 11月, 2003 21:32

Hi Mr. Chan,

From the previous post you mentioned the Zitong coating has some red-colour casting. Can you tell me your general impression with their coating?

Regards,
David
:)

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