Electrochromism for astrophotography

[Annehouw]

Here, there and everywhere, there are long threads on mono vs OSC. Ignoring the intricacies (and (non-)validity) of the arguments pro or contra, there is a lot to be said for mono in astrophotography. The practical side is that some (a lot?) of us are using a camera that is placed in the light beam. RASA, hyperstar and in my case hypergraph. Putting an unwieldy filter wheel in the lightbeam is a big no-no.  Changing filters in a filterslider manually can be done (and that is how I started) , but is rather tedious.

Thinking of solutions, I have thought of various mechanical alternatives for a filterwheel, but none of these solutions are real, practical, repeatable or stable. So a mechanical solution seems to be a dead end. 

So what if it could be done non-mechanicaly....and indeed, this could be done in theory. There is a class of "electrochromic" materials that can change color under the influence of an applied voltage. I found a recent mention of "smart glass" that can change color (and very rapidly as well). The researchers also claim that they can isolate small parts of the visible spectrum. If this would be narrowband enough is not clear from the description. 

These kinds of materials are commercially being used, but mostly as a means to darken glass (e.g. in glass windows). 

This is just a bit of fun in thinking of "our" problem and I have no idea on the practicality or affordability for our hobby, so it goes here into the science forum.

Here is the link  New electrochromic material can rapidly change color through electricity and there is a more elaborate pdf if you click through to te website of the Journal of the American Chemical Society. 

Edited March 16, 2022 by Annehouw

[vlaiv]

Interesting idea.

I guess main issue will be getting something that is of optical quality - flat enough so it does not introduce too many aberrations when put in optical train.

 

[Annehouw]

Yes, indeed.

The more I read about it, the more I get the feeling that this could work for LRGB. The electrochromic materials are available as coatings, so a thin layer on flat glass would give the optical quality probably: https://www.european-coatings.com/articles/archiv/electrochromic-polymers-create-coatings-that-change-colour

Now, a lot of things need to come together.

Bandpasses that are fit for our purposes so that  a complete visual spectrum is rendered. Very low or non existent hysteresis so that the fidelity does not diminish.

Enough color density by the thin coating. 

Narrowband is another interesting challenge. But how nice it would be to tune the filter to a specific wavelength electronically (instead of tilting as currently in test at the dragonfly array).

I have my doubts whether the amount of research needed is warrented by this part of the amateur astro market, but who knows.

Edited March 17, 2022 by Annehouw