Why Baader solar film can produce good quality image?

oldfield

Why wrinkle does not matter?  Is that because it's so thin?

mca

I don’t have best answer, but I guess that if the thickness of the film filter is thin enough, the effect of surface wrinkles on the image quality can be minimized. We can experiment with an analogy. Put a 食物保鮮透明膠紙 in front of a bino objectives. We probably see an image without noticeable quality loss. But if add more and more plies of 保鮮紙 before the bino, we would notice a degrading image.

I also found the astronomics.com have this wording…
http://www.astronomics.com/main/ ... PGTCJ9N57AP6LN5DRA0

“A Celestron Astro Solar Film filter usually appears wrinkled on first inspection, but this has no effect on the optical performance. The best resolution is obtained when the filter is slightly relaxed or wrinkled. Because the film is so thin in relation to the wavelengths of visible light, light rays pass through the filter unaffected by any deviation from a flat filter surface due to the wrinkles. The Sun’s rays are through the filter so quickly that they simply don’t see the wrinkles. As a result, Astro Solar Safety Film is diffraction limited…. (Hahaha, Celestron sells film filter, OEM from Baader ?)

My 2 cents

AC

mca

I found this text in astronomics.com interesting
"..... The best resolution is obtained when the filter is slightly relaxed or wrinkled. "

What I imagine is that if you try to make the film filter wrinkleless, you are actually pulling the film under tension. The tension will degrade the material characteristics and hence the image resoltion.

AC

oldfield

thanks...

time to do experiment, I shall put some 保鮮紙 in front of a refractor to try it out at higher magnifications...

CHYeung

The Baader Solar film and Astro film are highly homogeneous but common cling wrap  film (食物保鮮透明膠紙) is less homogeneous, so they will show differences in performance.

oldfield

Good point, thank you.

But I wonder if the wrinkles would render the homogeneity insignificant?