www.astrocafe.hk

用webcam拍攝太陽需要帶電腦和購買webcam，如果覺得不方便，用單鏡反光機拍攝的效果又如何？P-M Heden用單鏡機拍攝過不少精彩H-alpha相片:
http://www.clearskies.se/Gallery%20The%20Sun.htm

前數天我把Canon EOS40D接駁LS152T和B1800阻隔濾鏡，試試拍攝效果。鏡的口徑是152mm，焦距為900mm。

首先，我發現太陽表面圓盤上毛絨絨的細節在live view中幾乎完全看不到，如果沒有太陽黑子，是很難對焦的。我用ISO100拍攝，發覺曝光要1/10s才足夠。

一般來說，太陽邊緣日珥和太陽圓盤需要不同曝光時間。不過你也可以用只一張日珥曝光正常的相，然後用它的綠色通道作為太陽圓盤(可參考Sky & Telescope July 2004)。附圖為原相和處理後的圖，沒有疊相。

Thanks for sharing! It is not bad! Let me try it.

DSLR需要更換原裝阻隔濾鏡嗎？

Robin 寫:DSLR需要更換原裝阻隔濾鏡嗎？

No, the 40D I use is not modified.

David 寫:一般來說，太陽邊緣日珥和太陽圓盤需要不同曝光時間。不過你也可以用只一張日珥曝光正常的相，然後用它的綠色通道作為太陽圓盤(可參考Sky & Telescope July 2004)。附圖為原相和處理後的圖，沒有疊相。

请教David大侠，使用什么软件处理的？能说说过程吗？？很有性趣

shuimouzi 寫:请教David大侠，使用什么软件处理的？能说说过程吗？？很有性趣

I used photoshop. Please give me some time to write the steps.

Thank U very much!!

But can U write the steps in Chinese ? If not , I must use the English-Chinese dictionary.

shuimouzi 寫:Thank U very much!!

But can U write the steps in Chinese ? If not , I must use the English-Chinese dictionary.

Usually, David's paper is very easy to read if you took your attention on it.

Robin 寫:DSLR需要更換原裝阻隔濾鏡嗎？

I think this is one of the keys, that filter cuts H-alpha exactly just like as it did on DSO imaging. So, it's a hindrance indeed.

oldfield 寫:I think this is one of the keys, that filter cuts H-alpha exactly just like as it did on DSO imaging. So, it's a hindrance indeed.

Thanks for the tips. May be I'll try to shoot with my mod 350D sometime. But without the live view, it is going to be more difficult!

Anyway, webcam seems to work best for the sun rather than the DSLR.

CANON 50D冷卻天文機
像機設定為黑白
DPP處裡輸出
REGISTEX疊圖處裡
PS處裡與合成

wyk 寫:CANON 50D冷卻天文機
像機設定為黑白
DPP處裡輸出
REGISTEX疊圖處裡
PS處裡與合成

謝謝分享，細節很豐富。

能否分享多點資料？例如疊合了多少圖？用了Lunt的那支望遠鏡？曝光時間和ISO是多少？

wyk 寫:CANON 50D冷卻天文機
像機設定為黑白
DPP處裡輸出
REGISTEX疊圖處裡
PS處裡與合成

wyk兄抱歉，我不小心弄掉了你的照片，請重新上載，但不要"插入文章"，那樣看帖時只要點擊一下照片便可看到全圖。

David 寫:一般來說，太陽邊緣日珥和太陽圓盤需要不同曝光時間。不過你也可以用只一張日珥曝光正常的相，然後用它的綠色通道作為太陽圓盤(可參考Sky & Telescope July 2004)。附圖為原相和處理後的圖，沒有疊相。

為甚麼原相會有一個明顯的圓圈在太陽邊緣？

mwtse 寫:為甚麼原相會有一個明顯的圓圈在太陽邊緣？

There are a few strange things in such photo.

1. Theoretically, only H-alpha light enters the camera. Then how come there are green and blue signals in the picture?
2. The central part of the sun is dimmer, rather than brighter than the rest of the solar disk.

David 寫:1. Theoretically, only H-alpha light enters the camera. Then how come there are green and blue signals in the picture?

May be the filter before the green pixel is not perfect, it allows a small amount of IR to pass though, so the CCD will get some exposure.

David 寫:2. The central part of the sun is dimmer, rather than brighter than the rest of the solar disk.

Not quite understand what you mean??
I just find that, the solar disc is not even in brightness, but the unevenness is not centered at the centre of the sun. Is the sun framed at the centre of the field of view?

1. The outer part is brighter since it's overexposed in red (see 2, if you have signal leakage in green/blue, that means you're overexposing red since it should be purely red if properly exposed)

2. The central part is dimmer since it's a result of signal leakage into green/blue channels