www.astrocafe.hk

近月比較懶惰，目視太陽多，拍攝很少。今天的日珥很美，作了一些拍攝，也用binoviewer作觀察。

H-alpha: Lunt LS75F unobstructed + APM80/480 + DMK41
Calcium-K: Lunt CaK module + APM80/480 + DMK41
目視: Lunt LS152T + Denk II binoviewer

視寧度很差，相片質素很一般。

補上一些活動照，那個飛龍般的日珥在binoviewer下非常震撼，可惜沒有帶Televue Panoptics來看，只用了普通Plossl。有些同學認為用Binoviewer令日珥變得頗暗，反而單眼更精彩。不過binoviewer帶出如同在太空觀察太陽的感覺，單眼則無法做到。

全部人同意的一點是，有LS152T，什麼LS100T或LS75F也沒有人有興趣了

LS75F挺可憐的....

有機會分享一下Plossl, Nagler, Panoptics, Ethos等在太陽上的表現，特別是雙目的表現。

Binoview 配 H-alpha 效果很好, 口徑夠大一定要用

但廣角目鏡作用不太大, 因為 blocking filter 的大少限制了, 等同是 field stop

oldfield 寫:Binoview 配 H-alpha 效果很好, 口徑夠大一定要用

但廣角目鏡作用不太大, 因為 blocking filter 的大少限制了, 等同是 field stop

This is an interesting point. May be I'll try to experiment with this with my setup. I'll also see if B1200 and B1800 make any difference.

I agree with Oldfield. When I watch with LS60T + B600 + binoviewer, I could not move my head, otherwise the Sun disappeared. The small blocking filter certainly narrow down the effective FOV.

Lunt always suggests that users consider a larger blocking filter for imaging or binoviewer. This is because such uses require more room for backfocus, so the blocking filter is likely to be closer to the front of the scope when compared to visual use. i.e. the blocking filter must be moved further up the light cone. A larger blocking filter can prevent cutting off some light near to the edge of the light cone.

So I'll test on B1200 and B1800 and see if ordinary plossl and wide-field eyepieces make any difference.

I remember a crazy setup we did for fun a few years ago: quadruple stack of 100mm filters + Denk II binoviewer + two 13mm Ethos

David 寫:A larger blocking filter can prevent cutting off some light near to the edge of the light cone.

我連LS35T也是配B1200的：

viewtopic.php?f=15&t=32

David 寫:I remember a crazy setup we did for fun a few years ago: quadruple stack of 100mm filters + Denk II binoviewer + two 13mm Ethos

通光率只有40%，頻寛可能只有不足0.4A，日珥都不見了，只剩下一個週邊昏暗的日面，活躍區還是很高對比的......

以上只是我的想像，如有雷同實屬巧會　 　

oldfield 寫:Binoview 配 H-alpha 效果很好, 口徑夠大一定要用

但廣角目鏡作用不太大, 因為 blocking filter 的大少限制了, 等同是 field stop

今天用LS100T作了一簡單測試，看看12mm的廣角目鏡比12mm的普通目鏡是否有分別。

出動目鏡：
1. Televue 12mm Nagler廣角目鏡
2. Baader Hyperion 8-24mm 變焦目鏡，設定為12mm (我沒有12mm的Plossl)

首先用B1800 blocking filter，用Nagler觀察，把太陽邊緣放到目鏡視場邊緣 (即是剛好仍可看到全太陽)。然後轉用Baader Zoom，立刻一部份的太陽看不到了，即是在視場外，可見廣角目鏡有其作用。

我的學生也試過用Baader先，把太陽邊緣放到目鏡視場邊緣 ，然後一轉Nagler，廣角目鏡內的太陽周圍還有很多空位。

用B1200的效果一樣，可惜我沒有B600作測試。