香港天文論壇

漏了一些，全句應是“通過望遠鏡，用肉眼看太陽，你衹有兩次機會”。

左眼一次，右眼一次。如用雙筒鏡則衹有一次機會。

我可能是這句話的其中一個原創者。


YCH

Bravo!

Congratulations, this is a very good piece of work.


YCH

我给宇宙下了一个定义：星球间自转一周地球日之比，等于星球核心物质质量之比，等于星球有效电磁场长度之比。通过此定律，可以轻而易举地计算各星球，就拿木星为例：木星赤道上自转周期9小时50分30秒， 木星的赤道半径为71400公里，按着：“星球间自转一周地球日之比，等于星球核心物质质量之比，等于有效电磁场长度之比。”计算木星可以得知：地球自转一周为一天，木星自转一周为0.41天，地球核心物质铁的半径是51.847公里，计算木星的核心物质铁的半径是21.26公里。经过计算得知地球有效电磁场距地球核心物质半径以外长12848.37682公里，计算木星有效电磁场的长度为5268.511027公里，拿木星...

Wah!! 寫:Baader Solarfilm 新買回來是安全的.
但是接觸空氣時間長了, 便會出現小洞等氧化現象, 這時候就不太安全, 要換過新的了.

有時都很矛盾, 買一塊玻璃濾鏡能夠耐久使用, 但是顏色方面, 仍然是喜歡 Baader Solarfilm 更多......

All solar filters will have some tiny pin-hole on the coating. Even my Thousand Oaks Glass Solar filters come with tiny pin-holes when they are new.

YCH

TONGKW 寫: （小心安裝時唔好弄穿濾膜，否則會有危險，可以放近在100watt燈胆前睇下有冇穿孔）

太陽濾膜(Baader Solar Film)用作目視觀測要買密度=5.0 果款 [Density 5.0]

Normally, there are some tiny pin-holes on the coating but they will not do a lot of harm except lowering the contrast.

YCH

sbod 寫:http://www.apotel.com/surplusoptical.htm

到底什麼人會買呢類東西?

唔似係攻一般ATMers 市場......

天文台/天文館應該有辦法買到所需的零件......

難道係collective items!?

Yes, those are collector items. Jaegers was a famous company in the 70s selling a lot of those "large" achromats.

YCH

The Maxvision ED80 does not come with a finder or eyepieces. You need a finder (an aiming telescope) to help you pointing the telescope at the target and you need eyepieces to get an viewable image. You may need 2-3 eyepieces giving magnifications between ~20x to ~100X. You may also need a star diag...

In the old days, it was recommended to use Huygean or Ramsden eyepieces for solar projection. The H or R eyepiece is the simplest eyepiece having two separated singlets only. Other eyepieces have cemented elements, the cement may melt (if it is cemented in the old way with Canada balsam) or the elem...

Wah!! 寫:原來新型的PST唔可以用呢一招.

看來要改裝 TouCam 才有機會合焦了.

For my "repaired PST, the focal plane can be adjusted by the focuser to just a few mm outside of the eyepiece holder. For the ToUCam, the CCD is locate quite deep in the body; so, you have to modify the ToUCam.

YCH

搞了一天~終於把前輩說的這個部份拆下來了 不過~如果直接鎖上右邊這個套筒~接上ToUCAM 左邊這個不裝~會因為少了左邊底部那片濾鏡 感覺ToUCAM爆亮~調到1/10000秒曝光還是太亮了 而且左邊這個套筒跟您貼的照片上不同~它的底部沒有濾鏡? 不知前輩處理時有特別要注意的地方可以建議嗎? 感謝~ The older model do not have filter at the lower section while the newer version and those "repaired" PSTs have the lower filter. The "old" PSTs have...

剛找到壹段由壹位著名外國專業太陽觀測作家的報告，內有說UV/IR大部份被玻璃吸收了。 http://www.cloudynights.com/item.php?item_id=109 QUOTE”Some people think that a Herschel Wedge is a very dangerous accessory to observe the Sun due to the UV and IR radiation, but I think they are wrong, because you have to remember that the deep UV radiat...

The Herschel Wedge Solar prism discussed here is different from those encountered years ago thar comes with many cheap refractor packages which were proved to be unsafe. The new type of Intes Herschel Wedge Solar Prism discussed here (as well as the ones from Baader in 1.25” and 2” format) are both...

The Herschel wedge uses the reflection off an uncoated glass surface to reduce the light intensity. As we know, uncoated glass surface will reflect about 4% of the incident light*. However, almost the whole spectrum including UV and IR are reflected to about the same extent. In other words, the Hers...

Thanks for your clear explanation: yes, I agree some what different of the explanation between contrast and dynamic range. By wiki: http://en.wikipedia.org/wiki/Contrast Some other people from outside use this terms (contrast) and i also agree the effect of result is quite similar, Similar to the s...

謝謝你既資料: >dynamic range< 或者可否說是contrast普遍是CCD/CMOS 的問題,唯有希望佢地已經研究得較好, 見有其他一些討論都幾實用; 不過最令人欣喜既係佢地表示會普及應用, 如果唔用冷卻可以影到三兩分鐘已經好好了。 ps 點解咁耐先將研究作普及化...係咩原因, 分享下等...可以了解多一d都好 :) Sorry to reply in English. I can only input Chinese by writing pad and that is very slow. Dynamic range is not the same as contrast...