C6+0.63reducer 有黑角

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cwlam
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C6+0.63reducer 有黑角

文章 cwlam » 週一 19 10月, 2009 20:10

點解用C6+0.63reducer+40D 影相會有黑角?
是否T-adapter長度不合
有無好建議?

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Subaru
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文章 Subaru » 週一 19 10月, 2009 20:18

如果用原廠T-adapter, 係會有暗角(field illumination, vignetting)而唔係黑角, 此乃正常物理現象.

如果要有比較平均的field illumination, 用一支astrograph會較為適合.

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鄧登凳
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文章 鄧登凳 » 週一 19 10月, 2009 23:15

樓主: 你用什麼牌子的減焦鏡?

Subaru: C6 連減焦約4000 港元, 但小的advanced astrograph都要4000 英鎊 [頭暈目眩] [淚奔] [冷吱吱]

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Skyobs
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文章 Skyobs » 週二 20 10月, 2009 02:25

C6的visual back只大概1.25",APS相機難免有點暗角. 做好flat-field可減少問題.

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cwlam
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文章 cwlam » 週二 20 10月, 2009 08:56

鄧登凳 寫:樓主: 你用什麼牌子的減焦鏡?

Subaru: C6 連減焦約4000 港元, 但小的advanced astrograph都要4000 英鎊 [頭暈目眩] [淚奔] [冷吱吱]
I use meade 4000 0.63x reducer/flattener...

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鄧登凳
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文章 鄧登凳 » 週二 20 10月, 2009 10:20

cwlam 寫:
I use meade 4000 0.63x reducer/flattener...
Let me try such a combination with my ASC DSLR and tell you whether there is significant vingetting later. :)

Probably, doing a flat-field adjustment as Skyobs suggested may help.

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cwlam
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文章 cwlam » 週二 20 10月, 2009 15:08

鄧登凳 寫:
cwlam 寫:
I use meade 4000 0.63x reducer/flattener...
Let me try such a combination with my ASC DSLR and tell you whether there is significant vingetting later. :)

Probably, doing a flat-field adjustment as Skyobs suggested may help.

Attached the photos showing the "暗角" problem... any suggestion to minimize the problem?
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鄧登凳
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文章 鄧登凳 » 週二 20 10月, 2009 15:31

Repeated :oops: please delete :!:

See next post :arrow:
最後由 鄧登凳 於 週二 20 10月, 2009 15:43 編輯,總共編輯了 1 次。

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鄧登凳
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文章 鄧登凳 » 週二 20 10月, 2009 15:40

I intend to try some without the camera extension tube or without the visual back. But I am not sure whether that will solve the problem.

However, with direct t-mount to C6, I remember there was not that much vingetting as in your second photo.

Apparently, the brightness of the vingetted area may be adjusted by taking some "flat-field" photographs (I think pointing to the grey sky without "the floating ball " and the roof-top will do) and than use photo-editing software to adjust the brightness according to the "flat-field" photos.

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文章 鄧登凳 » 週六 07 11月, 2009 16:50

Sorry that there is much delay in testing this.

Two photos all with Celestron 6 SCT and Sony Alpha, (1) 0.63 reducer using original visual back and 1.25 inch t-ring nose. More vingetting (黑角). (2) 0.63 reducer but 2" extension tube and 2" t-ring nose. Some but less vingetting.

Suggestion: Use a 2 inch connection system and use flat field to correct remaining vingetting.
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文章 cwlam » 週三 11 11月, 2009 12:09

Dear 鄧登凳,

Thanks for your advice...

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