太陽觀察 --- Etalon空腔物料的選擇， 能量濾除濾鏡 ERF(5)

[Wongsir]

Etalon空腔物料的選擇
‧ 市場上主要用兩種物料來製造etalon的空腔
‧ Coronado 選用比較穩定的空氣免除恆溫設備的須要；但須採用專利的中間結搆
‧ Solar Spectrum及Daystar都採用fused silica；因厚度及折射率都對溫度敏感，故須配合恆溫焗爐來用(一般40-50°C左右)





雙重 Etalon
‧ 一般etalon的頻寬大概是0.7Å
‧ 若要收窄頻寬可選擇雙重etalon
‧ 但兩隻etalon是須要匹配中央頻率以收窄頻寬
‧ 兩隻etalon的中央頻率是要有稍微的差異以達到整個系統的頻率響應收窄
‧ 若兩隻etalon的中央頻率是完全一樣的話祇會影像變黑但頻率是完全不會收窄
‧ 可選擇etalon在鏡前重疊或一個鏡前而另一鏡後





鏡前ETALON







鏡後ETALON







ERF濾鏡
‧ 通常鏡前的ERF濾鏡是採用德國Schott廠所生產的RG系列玻璃
‧ 它是用乳化方式染紅，對光熱較為穩定
‧ 吸收紫外線及可見光，容許紅內線及近紅內線的光透過
‧ H-alpha一般是用RG645規格(截止頻率)







Ameobahydra
10-12-2005

[HK.Raymond.Tse]

Tilting method (Coronado's Solarmax and Daystar's T-Scanner) is a good method for bandwith down to 0.5A.

For even narrower bandwidith (0.2A-0.45A), themo-electric oven is more appropriate. Cons : usually require F30 (thus high magnification) and electricity (less portable).

[天狼]

我這有一個，但是目前還沒拍出特別好的照片。

[Wah!!]

為何太陽 H-alpha 的 Etalon 濾鏡, 總是金色的?

[破冰]

Coronado 是美國專門生產太陽望遠鏡的，而它的望遠鏡鏡筒就是金色的，前置濾鏡為了使整體美觀，而使用金色（個人見解）。

Coronado 的望遠鏡很貴，不就多了個太陽濾光鏡，換成人民幣要上萬。
感覺像打劫的。

[豆豸苗]

repost lost post:

Gold has the highest thermal stability to withstand the heat of the sun and is most suitable for the reflective surface of the interference filter.

Coronado filters are expensive but do you know how difficult and the cost to polish a pair of parallel plane surfaces to achieve optical quality of 1/30 wavelength?

[Wah!!]

Quote from CloudyNight Forum:
http://www.doylestowndesigns.com/astron ... sary.htm#3


Q: Why are solar H-alpha filters so expensive?

A: Because you need an extremely narrow bandpass to observe the chromosphere. The photosphere is extremely bright so if your bandpass is much larger than 1 angstrom, emission from (or absorption by) the chromosphere is overwhelmed by the continuum emission from the photosphere. In comparison, a Lumicon O-III filter has a bandpass of 11 nm (110 angstrom).

The narrow bandpass is achieved using an etalon, which consists of two parallel surfaces with reflective coatings. The surfaces are made and aligned so that the separation is an integer multiple of 1/2 of the target wavelength, i.e. a multiple of 3281.5 angstrom. This separation must be accurate over the entire filter, and maintained at all times during use. Even a 0.1% variation results in a shift of 6 angstroms, which would be completely unacceptable. Typically the surface flatness and spacing must be accurate to 1/200-wave.

[hunter_大祭司]

Coronado 是美國專門生產太陽望遠鏡的，而它的望遠鏡鏡筒就是金色的，前置濾鏡為了使整體美觀，而使用金色（個人見解）。

Coronado 的望遠鏡很貴，不就多了個太陽濾光鏡，換成人民幣要上萬。
感覺像打劫的。

o吾知佢地的品牌濾鏡顧有size有乜選擇同可以比乜類型的鏡用呢？？？

[Wah!!]

http://www.coronadofilters.com

[hunter_大祭司]

http://www.coronadofilters.com

芬橋！