香港天文論壇

Dear astro lovers, There is always a big misunderstanding about black hole. A Black hole cannot swallow thing easily. Why ? Just think about this - will earth be sucked by our sun ? Will Hubble Space Telescope fall back on earth ? Of course not. If, all of a sudden, our sun turns into a black hole, ...

睇深空天體，應該用咩望遠鏡??用牛頓式定係用施密特-卡式?? Dear Mr. Brother, The only suitbale telescope for deep sky viewing is a Newtonian with alt-altz mount. Why? 1. Schmidt Cassegrain, refractor, Cassegrain ...etc all have eyepiece fitted on back of telescope. If you want to have a comfortable viewing position, you need ...

Dear Mr Wah, Thank you for your comment. However there are two points I would like to stress :- 點解第二次反射的要用平面,而唔用凸面呢?(好似有種卡式鏡係咁樣) Whether it is easy or not to fabricate a particular shape of optical surface depends almost entirely on whether there exists a practical method for testing that surface. F...

Mirror God, Are you going to grind the optical flat yourself ? Making a 8" optical flat is really a challenge! Wongsir 13-1-2004 Dear Mr Wong Sir, It is not that difficult to make an optical flat, since we can conveniently use the interference test to judge the figure during polishing. What really ...

Dear ATMs, For the 24 inch telescope that was proposed yesterday there exists an alternative design. The main idea is to replace the f/3.5 primary mirror with a f/7 one. The focal length will increase from the original 84 inches to a 168 inches ( 14 feet !!). The telescope will be extremely long, vi...

Dear Mr. Subaru, There is no need to cover everything with black clothes, as experience told by the 14 inch telescope in Water Mouth, all we need is to cover up the opposite side of the eyepiece, all stray light ill be completely cut away. Although the struss tude is very thin, it still keeps the al...

Dear Mr Brother, To me my limit is a 20 inch teleascope for one men in Hong Kong, 2 men outside Hong Kong. I seldom use a 20 inch Newtonmian, my favorite is a 14 inch Newtonian, very handy for one men travelling to Water Mouth or Shek O, by bus and MTR. Such telescoope is not available in market, yo...

Dear sky lovers, Recently one of my friends had purchased a new EQ-5 at HK$800 from ASp Liu Street. I finally had a chance to have a real look onto this famous product from China. What surprised me was that it was a copy of Meade LXD55, they looked nearly exactly the same, except that LXD55 has a sl...

Dear ATMs, I have planned to start work on my next challenge. After very careful consideration this will be a 24 inch telescope incorporating an ultra thin mirror of thickness 1 inch. This newly designed telescope is by no means to replace the existing 20 inch telescope which has been serving me, un...

Dear Old Salt Fish, If possible please write in English or use BIG5 code for Chinese writing. My computer cannot decode your Chinese characters and so it is tough for me to understand what you are trying to communicate. Judging from your diagram, ( I can't see your words ) there is a contaimnation o...

I suggest taking one more image at shorter exposure & stack, the inner portion of Orion Nebula will be more clearly defined. Anyway, the nebulosity is rich! PS: F.L. of GT-68 is 600mm, GA-4 with built-in 3x barlow, using 5mm eyepiece, will give 360x (perhaps 300x in your data was wrong calculation?...

影完這一張後，又落幾日雨，想補多張都冇機會 ！！ :( :( ck Dear CK, You should go to XingLong where there is clear night for every night. While we were there, all we hoped for is one cloudy night so that we could have a good rest. Thanked god we finally had a total 3 hours of clouds overhead one night but "unfortunately" t...

Date :- 24 Dec, 2003 Place :- XingLong, Beijin observatory. Lens :- Takahashi FSQ-106 Camera :- Canon EOS-10D Exposure :- 10 minutes at ISO800, single frame Equatorial Mount :- Takahashi EM-10 USD (II) Guiding telescope :- Mizar GT-68 at 300X Guiding eyepiece :- GA-4 + or-5mm Best regards Chan Yuk Lun

Date :- 24 Dec, 2003 Place :- XingLong, Beijin observatory. Lens :- Takahashi FSQ-106 Camera :- Canon EOS-10D Exposure :- 10 minutes at ISO800, single frame Equatorial Mount :- Takahashi EM-10 USD (II) Guiding telescope :- Mizar GT-68 at 300X Guiding eyepiece :- GA-4 + or-5mm Best regards Chan Yuk Lun

Date :- 24 Dec, 2003 Place :- XingLong, Beijin observatory. Lens :- Takahashi FSQ-106 Camera :- Canon EOS-10D Exposure :- 15 minutes at ISO800, single frame Equatorial Mount :- Takahashi EM-10 USD (II) Guiding telescope :- Mizar GT-68 at 300X Guiding eyepiece :- GA-4 + or-5mm Best regards Chan Yuk Lun