Quote:
Originally Posted by bojan
Hi Eugenio,
My point of view is very simple, I don't see the benefit in using LCD as a filter, especially in front of the lens (objective). The optical quality is not a small issue here - the only reason why solar filter does not introduce (a lot of) optical distortion is because it is VERY thin... but colour LCD is a multi-layer assembly, very different from neutral filter (with a lot of transparent wires in it), and it is not designed or manufactured to be used as a filter in front of the objective lens of the telescope (I am guessing the price would be much, much higher in that case). The fact that user does not see a problem with LCD glasses is simply because the magnification is not involved... with the telescope however, it is a different matter. So, your test may be able to prove the concept in terms of colour filtering... but I doubt you will be able to progress with this much further than that. Mind you, if you do, I will try to be among the first to congratulate you 
As you pointed out, the LCD filter will take out at least 66% of incoming light (because only one third of the incoming area is available, the rest is blocked with other colour pixels) but the same happens with Bayers martix as well.
Conventional filter, on the contrary, has (almost) 100% transmission for the central wavelength, no blockage or reduction of aperture. Of course, there is a need for another 2 exposures to get the full spectrum, but the overall result is still 3x better in terms of total photon collection.
So.... my point of view is not to attack you but to try to direct you to think realistically, and to point out the obvious problems and issues with the idea. You have to be able to answer my concerns with compelling counter-arguments and/or repeatable test result, right?
Also, you may wish to consider why this idea is already not being used - maybe there is a good reason for this being the case?
In my school days, I dreamed about using mylar foil and vacuum chamber behind it to produce a parabolic mirror. Or a mirror cast from plastic and aluminised.. I even made a prototypes and they worked (in a sense that they focussed the light in a small area) buy that was all... Many others before and after tried the same or similar, even unbelievably more complicated assemblies were made to achieve the minimal acceptable optical quality and stability .. and we are still using solid glass mirrors. |
Hi Bojan,
So you don't believe that even if the LCD matrix used has fairly good optical transparency, colour saturation and optical resolution, it would not be useful for solar observations when used with such a filter as the Ba'ader solar film? Particularly when programmed to bandpass good detectable energy levels of the Calcium K Line and Hydrogen Alpha wavelengths of the visible light spectrum? In my opinion, if the LCD Digital Filter could be used for only that, it would be worthwhile just in the $$$$ savings. Then again, that is just my opinion.
I've used Ba'ader solar film before, and there is quite a lot of white light that can be tapped at the eyepiece. And if you eat a lot of carrots/sardines (phosphorous and Vitamin A) and your eyes have high cornea light sensitivity, it's even more pronounced and can actually be uncomfortable.
Bojan, I admit I sound a little convoluted at times, that is because I'm also trying to explain it all in a language that non-technical people can also grasp. It might take you a couple of times reading what I have written, but in many ways I have covered a lot of what you are already pointing out.
I can see you are an extremely intelligent individual, and I hope you will stay with us here for a while and keep sharing your scientific and intuitive insight and knowledge!
I value everyone's input on this project and so do others. So please feel free to contribute as little or as much as you feel comfortable with. We really enjoy the interaction.
Back to work now.....
:comput er: