Hi Malcom,
Thanks for the input. I agree in regards to mono imaging sensors, they would yield a better result.
When you made reference to the amount of green sensors/pixels in relation to red and blue, did you refer to the Bayer mask on colour CCD's?
Anybody want to know more? click here:
http://en.wikipedia.org/wiki/Bayer_filter
Good thing about using a RGB LCD screen as a Digital Filter to slice up the visual spectrum is that LCD RGB matrix is more uniform than a Bayer mask for a CCD sensor. Therefore, you don't have to compensate for extra green visual data.
Anybody want to know more? click here:
http://en.wikipedia.org/wiki/TFT_LCD
Malcom, I understand what you mean in regards to the sharp roll-off.
A more gentle sinusoidal roll-off can be accomplished using the LCD Digital filter if you require it. Other waveforms can be accurately approximated such as, square wave, Triangle or even complex waveforms for the Spectral Bandpass Envelope. Another feature is, you can also shape a Spectral Bandpass Envelope that conforms to any given linear visual spectral range. Although the Spectral Bandpass Envelope is not solid, it should be able to give the same sort of results using long exposures when used for CCD imaging. Take note though, the Digital filter does goble up aperature to varying degrees depending on the Digital Spectral Envelope Filter dataset used
so longer than usual/desired exposures are most likely required in some cases. That drawback should not be drastically evident in LRGB imaging using an LCD Digital Filter, therefore longer than usual exposures should not be required.
The Bandpass envelope can be programmed as a dataset in software. The LCD Digital Filter window can then be made to respond according to the values in the dataset. Not only hue/colour values but, neutral density values can also be simulated/created. If using specific R, G or B filtering, then 256 different Neutral Density/shade values are possible per R, G or B. This would be good for moon observations especially. The neutral density values in the dataset shape the height, of any slice of the Spectral Bandpass Envelope.
going off with more jargon
The visual light spectrum takes up about 350nm of bandwidth approx.?
Want to know more? click here:
http://en.wikipedia.org/wiki/Visual_spectrum
For complex bandpass filtering, the "Bandpass slices" or, if you like, theoretically the smallest, individual segment of the bandpass filter, capable of being created using a 24bit LCD Digital Filter is:
0.00002086162567138671875nm (nanometres).
or
350nm / (2^24bits)
24bit colour resolution for LCD monitors allow 16777216 possible different hues/colours to be filtered through the LCD matrix. 32bit LCD monitor even more!
Keep in mind though, only one slice of the Spectral Bandpass Envelope can be used per frame that the LCD switches at so, in one second you can display at the eyepiece 60 viewable slices of the bandpass filter visual data.
If you have a more advanced LCD screen as The Digital Filter then, perhaps 120 frames per second or, 120 slices of the bandpass can be displayed in 1 second. The better the LCD used, the faster the framerate the more accurate the bandpass filtering can be. Some LCD screens actually don't turn pixels off unless they change colour, rather than turning off and on 60 times per second. These non-flickering LCD screens would be the best to use as an LCD Digital Filter. Soon all LCD will be that good.
I can see Malcom how digital imaging would yield much better results when using complex Spectral Bandpass Filtering and long exposures of this visual data.
I have found that cheap low contrast LCD screens used as LCD Digital Filters give less results although, they can still enhance and contribute to the viewing experience when used for Moon and planetary observations. Believe it or not, I have not tried imaging through a LCD Digital Filter yet
My main focus is on the software for the LCD Digital Filter and getting my 8" Saxon Mak up and running for testing it, not to mention other projects on the drawing board. I also have a Canon 550D DSLR on it's way to me which I will definately try out some imaging with.
I really need more aperature for advanced testing of The LCD Digital Filter. From what I have calculated, large aperature optical systems will benefit the most from a LCD Digital Filter.
Anywhooooo, sorry if I tend to rattle off a bit. I get like that sometimes when I have to much coffee
BTW, I've ordered one of those little 1.5" LCD photo frames, and hope to test it out to see if it makes a decent LCD Digital Filter for eyepieces. If it works...could be a good, portable economical solution. I will post on this later when i've done some testing when it arrives and i get the time
Will catch up later, have a good one! and take care everybody!