看到CERF 的說明，穿透帶寬FWHM 為45nm
說明如下
http://www.alpineastro.com/Reference_Docs/CERF-Filter-SafeUse.pdfBAADER C-ERF FILTER
CAUTION!
"Baader C-ERF Filters" are used only for Hα solar observing together with telescopes which are equipped with a "Solar Spectrum" Hα filter! Never directly look at
the sun through a telescope which has only the C-ERF filter mounted as protective
device. Severe eye damage may occur!
The BAADER C-ERF filter is equipped with a proprietary IR-reflector coating. This additional 28-
layer dielectric DWDM-coating delivers a "COOL"- beam of solemnly red light, only opening a
spectral window of 45 nm HBW! This precaution has some very important effects:
- The IR reflective coating dramatically reduces the thermal energy that can reach through the
telescope onto the Solar Spectrum filter. This prevents the Solar Spectrum filter from aging
其中誇大的是28層介電質DWDM 鍍膜， 其實不多 也不難
眼鏡上的紫衣 茶色 抗反射多層膜，有的廠商也用的是"DWDM"鍍膜技術
但鍍膜廠商也許不說或也許不知道，因為不是很重要 也不一定有人關心
另外還有C+DERF
帶寬更寬 100nm
倒是 有人可以跟我說 人眼的安全波長可以到哪裡
這個 C+DERF 到1400nm以後就有能量跑了上來
那一段還是很熱
