內反射的可能成因?

oldfield

http://video.google.com/videopla ... 679533291&hl=en

請先睇睇上面段片... 我放塊 ERF 響支 C5 鏡前, 以減低太陽光強度, 但當然 ERF 減光並唔夠, 呢點似乎亦令到 internal reflection 問題出現

如果經埋 etalon 同 blocking filter, 就無咁明顯, 但其實仍然存在, 仲好形響成像既反差...

你見段片個 internal reflection 唔對稱, 係因為我特登斜左少少去 mount 塊 ERF, 當然斜得唔係咁多, 所以個影仲係出現...

問題係, 到底我應該再斜多 D 塊 ERF 黎 mount 佢, 定係應該用其它 approach? 因為塊 ERF 都幾重幾大, 唔係咁容易再斜 mount 多 D... 當然如果大家都覺得再斜 D 可以完全 solve internal reflection 呢個問題呢, 我覺得都值得再研究點搞佢

大家有無乜野諗法? ...

Thanks!

astroQM

I have the same problem using SM60 + Sky90. I've tried tuning the T-max and changing the distance between the filter and the lens (by simply pulling the dew shield) without success. But I don't recall having such problem with Celestron 4 inch f/10 refractor.

ericng

I have not much experience in solar imaging but just wild guess ... would it be solved by making te aluminum adaptor with elevated frontal plane for the ERF can be mounted more securely?

Eric

[ 本帖最後由 ericng 於 2008-3-1 18:25 編輯 ]

David^_^b

My experience in viewing partial solar eclipse in late 1995, which is my first time in using my J-brand solar screen for such purpose, which is the same as you.

As my scope is 8 cm f/7, I slight tilted of the screen (better with sticking taps on it) and saw the secondary image shifted out my my field of view (~1.5 deg in my 25 mm eyepiece), so I can continue my observation without such annoying light.

I saw your tapes and photos the secondary mirror image.  Would my solution applies if the tilting direction fit the imaging need ?

Of course, my solution is basically try-and-error. My 2 cents.

oldfield

Thanks all...

Actually, I've made a tilted cell for the ERF but the problem persists.  I believe now the internal reflection is caused by the blocking filter to the etalon, i.e. I need to tilt the blocking filter slighty.

CHYeung

I have similar experience with my SM40/BF10 set-up.  The reflection is due to the etalon (SM40).  The problem is more pronounce with a faster scope, with a slower (larger f/ratio) scope, the reflection is further away.

My solution is to tile the etalon a bit (out of best position), or rotate the etalon to the side where no prominence is seen.

C. H.

oldfield

Thank you for all the valuable inputs.

The blocking filter has a mirror like side (towards objective), and that's the original of the internal reflection.

For simple system like SM40/BF10, the internal reflection originated from the blocking filter can be solved by tilting the SM40, to make the internal reflection out of sight.

For my case, the internal reflection from the blocking filter goes to the internal etalon module (PST's one)... and it can also reflects to the ERF as well, but since I've tried to tilt the ERF but the internal reflection is still there, so my tentative conclusion is that, the internal etalon module should (also?) be tilted as well.