香港天文論壇

well processed.

(1) I see from your website that you used a Herschel Wedge on the APM 80mm refractor. Do you have enough back-focus to image the sun with a webcam or a DSLR camera? (2) What Blocking Filter do you use for Ha imaging with your LS152T? BF1200 or BF1800? 1. Yes for DMK webcam but I have not tried DSLR...

I use a 80mm/480mm with Lunt B1200 with no problem: http://www.astrocafe.hk/viewtopic.php?f=15&t=3477 The pic was taken yesterday with about 50% gain and about 1/100s exposure. I use DMK camera (mono) rather than DBK. Try a longer exposure for DBK. B600 and B1200 is certainly not an issue. It is har...

Many people see what they believe. Richard Feynman once said:

"The first principle is that you must not fool yourself - and you are the easiest person to fool."

It is actually a good thing that some students saw while some some students didn't see the phenomenon in the same school. It should really stimulated the students into thinking what makes one see and what makes one not see the phenomenon.

昇仔 寫:我認為 Noodle 這樣才是開始認真起來了.... [熱]

2x

I was looking at such info a few weeks ago for some special events (far from exhausive, obviously). It is not looking too good. 2012-13 03-12-2012: Jupiter at Opposition 48.4” 28-11-2012: Penumbral Lunar Eclipse 11-3-2013: C/2011 L4 PANSTARRS (Peak Brightness estimate: Mag 0.5) 25-04-2013: Partial L...

Very smooth animation!

同樣道理, 在無數業餘和專業的望遠鏡拍攝得清晰無黑滴現象的圖片後, 拍不清和看不清的人也應該了解到那黑滴現象是源自觀測者本身的器材/環境/技術限制, 並不是源自什么特殊的天文現象. I think the fact that more people in the past centuries saw much more prominent black drop says a lot about this issue, at least for ground-based (rather than space-based) observations. The limb darkening eff...

Just before 3rd contact.

Original videos taken with LS152T by Egret34. Processed by Photoshop and Avistack2. Each pic is a stack of around 200-400 pictures.

An easy-to-read article in Sky & Telescope: The Disappearing Black Drop

http://www.skyandtelescope.com/observin ... 38145.html

deleted (repeated posting by mistake)

Some more reference: http://www.transitofvenus.nl/blackdrop.html "The last couple of years the black drop effect was studied intensively, both from optical theory and simulation experiments. Images of the transit of Mercury by the TRACE satelite were analysed and numerical models were employed to ex...

看看這個由在太空中的、不受seeing影響到SDO所拍的, 留意金星的形狀和太陽邊的凹陷。 Yes, the same had been observed in 2004 in space. That's why black drop is also thought to be contributed from solar limb darkening (Seems that this limb darkening view is very much supported by Jay M. Pasachoff) http://www.astrosurf.com/stog/Travaux-Re...