香港天文論壇

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順豐越做越大,開始揀客,我試過淘寶買一樽粉狀物,順豐不肯送,但其他公司卻肯送. 所以建議找其他公司!

已pm

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I suggest you go to Apliu Street, Sham Shui Po, where there are a lot of camera shop selling optical equipment.

Dear Wah!, It will depend on how SHORT the time you mean. Because if the SHORT time approaches zero, no matter how little the mass is (the tiny clock), the power needed to accelerate it will also approaches infinity, as the formula goes: Energy needed to accelerate/time required to input = infinity ...

Dear Wah, When object accelerate from zero to a velocoty v, then it will need input kinetic energy 1/2m(v)square, where m is the mass of object. Although you input the same amount of energy to accelerate the object, but you want to accelerate in VERY SHORT TIME, that means you need a VERY HIGH POWER...

我想這是關乎人類科技水平問題.
但當加減速所用的時間接近零時,那加速器Power便接近無限大,你想這是可能嗎?

Wah!! 兄：

我的理解是這樣:

當哥哥離開弟弟加速至差不多光速時,哥哥會經歷巨大重力場(由加速引致),根據相對論,當物質於巨大重力場中,時間便會變慢,而當哥哥回程至地球時,也會經歷巨大減速(=巨大重力場),所以哥哥經歷時間較慢.
但弟弟在地球卻沒有經歷巨大重力場,所以弟弟時間沒有變慢.

那你是否建議用QHY5II + PHD or ASI120mc(既可當CCD camera, 又可作guiding camera)?

如果Nextguider 配celestron radial guider 再加Celestron C8 autoguilding 又怎麼樣? 容易對焦嗎?好用嗎?
我有 C8 + celestron radial guider, 正考慮買Nextguider!

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Funoooo,
Please see p.m.

小弟影天文相用tiff format 在DSS 做stacking ,完事後再用其他software轉做jpeg, 相片變得漆黑一片，有冇同好知我犯了什麽錯？