Henry Wu 寫:是否可請說明此 Filter 的功效
謝謝
I tried both CLS & P2. The P2 is not owned by me. I found that CLS has stronger light pollution reduction power. Both filters block the annoying Na light (589.0 and 589.6 nm)
http://en.wikipedia.org/wiki/Sodium-vapor_lamp. However, the CLS blocks yellow (around 570-590 nm) completely in the spectrum which make it impossible to image those DSO with yellow
http://en.wikipedia.org/wiki/Visible_spectrum. Although there are not much DSO with yellow, Rho Ophiuchi Nebula 星空調色盤 is one of those and is my favor. As u can see from my Ophiuchi Nebula photo, I cannot process out the natural color of Rho Ophiuchi Nebula. This frustrated me a lot. On the other hand P2 block only the annoying Na yellow lines and allow some yellow to pass. So P2 helps a lot in this situation. Well if u have enough money, it is always good to have both. As I mentioned, not many DSOs with yellow, CLS is useful in heavily light polluted area. While P2 is a moderate light pollution filter which enable some yellow to pass.
See these links for the spectrum response of CLS & P2:
http://www.astronomik.com/en/cls/astron ... s_full.png http://www.teleskop-express.de/shop/Bil ... transm.gif
發表於 : 2010-07-25, 12:41
