Adhesive Filter Film?

[gaseous]

Hopefully there are some well-informed people on this forum that can answer this for me. Is the process for creating astronomy filters such that it would preclude producing filters on an adhesive substrate rather than glass? I would assume a glass filter would produce a higher quality image, but it would be interesting, if possible, to apply an adhesive OIII/Ha (or similar) filter film to some reading glasses to see the effect under dark skies, or to create some "caps" for binoculars with filter film in them, or even to create your own filters at home that could be easily replaced if the film gets scratched. Apologies if this is the stupidest idea ever or has already been done - I owe you all 30 seconds of your life back for reading it.

[julianh72]

I don't know of any practical way of making quality narrow-band filters on a flexible adhesive film - such filters require multiple incredibly precise layers to be placed, and I imagine trying to do this on a flexible (adhesive-backed!) substrate would be a major challenge.

A more practical method is to just to mount a standard astronomical filter into an adaptor that mounts to the front of your glasses / binoculars / whatever.

A really simple method to fit an astronomical filter to a camera or pair of binoculars is unscrew the barrel from the bottom of a spare 1 1/4" or 2" eyepiece. Cut a matching hole out of a spare lens cap, and glue the eyepiece barrel to the front, with the filter threads projecting outwards - you now have a reduced aperture lens cover which will accept any standard astronomical filter. (If using binoculars, you can simply leave a lens cap on the second objective, or make two adaptors - but you will need two filters for best effect.)

You can easily make up something similar from sturdy cardboard or plastic sheet to fit onto just about anything.

You can also buy filter adapters to suit standard DSLR cameras - see this for example:
http://www.rspec-astro.com/dslr-adapter/

It shouldn't be too hard to make a filter adapter for almost any purpose. (You could even make yourself a filter-monocle, for a great "steam-punk" effect at star parties!)

[gaseous]

Cheers Julian, I gathered the process would have been a bit finicky, and your first sentence has confirmed that. I have enough trouble not eliciting laughs from my wife when attending star parties in normal clothes - a steam-punk inspired UHC monocle might be a bridge too far!

[Wavytone]

Julian,

Narrowband filters won't work on flexible film.

It's not that they can't be made - they could, but it would be pointless because as the film flexes this changes the angle of incidence of the light reaching the film, and that alters the passband wavelength. The result is a rather degraded filter that isn't narrowband anymore.