西藏天文台建立3年多,APO折射用過,最近又升級到OS RiFast 500 (1900 f3.8),細讀這篇測試報告,可謂於我心有戚戚焉
http://www.skyandtelescope.com/wp-conte ... iDK300.pdfQuote :
"The author never adjusted the scope's focus during the 15 hours of observing time (spread across two nights) during which he made exposures of the image.", "...during a 7-hour stretch when the focus also remained untouched. On both nights that temperature dropped more than 13F (7C) during the exposures"
"my scope traveled from Italy to New York, then to California, and finally back to Massachusetts in a rather unremarkable cardboard box surrounded by only 2 inches of polyethylene foam. Add to that the rough handling that equipment typically endures when displayed at trade shows, and you can understand why I was expecting the scope to be out of collimation when I finished setting it up in my observatory. It wasn't, and this fact astounded me." (這跟我在西藏暴力安裝時的情況一樣
viewtopic.php?f=12&t=1188&start=380#p24299 )
"....and a couple of 10-minute test exposures had stars only about 1.5" in diameter. This is extraordinary...."
當然,圈內至今仍流傳,甚至出自好些玩了天文很多十年的愛好者口中 "RC因為沒彗差,所以天文攝影表現最好" 等怪論。
要說明一點,我2001年跟德國下單,現時設於麥理浩夫人渡假村的APM 600口徑Classical Cassegrain,也要費一番唇舌,跟當時太空館顧問包括中大朱教授及創館長已故廖生解釋為何不用RC。
兩個天文台 - 白鷺湖天文台、西藏自動化天文觀測站
主鏡 - Officina Stellare 500 口徑f3.8 RiFast攝星儀、APM/TMB 254 f9 APO、SkyWatcher Dob 18、305 f8.5 牛頓鏡、Paramount ME 赤道儀
配件 - 2 full sets of Supermonocentrics、Baader Mark V Binoviewer、Ethos、Canon 5D Mark II Mod、FLI Proline 16803冷凍相機、Mercedes SUV
星河科研社
http://www.astro.hk 電郵
saviofong@astro.hk