Binocular Telescope and CCD cameras

[Karls48]

Hi All
I would like to combine composite video signal from two identical CCD cameras (but one colour on and the other BW) into one. Commercial mixers are out of the question as they are too big and too expensive. I have searched WEB but could not find the circuit diagram than would do it. I hope that there is expert on video signals processing who could point me in right direction. I’m think about building binocular refractor telescope from two 102mm F5 OTAs. Am I correct assuming that such a telescope would have effective aperture 144mm F3.4? This telescope would be set up only for imagining, not for visual observations. Of course I want first to see how the cameras would work together. Any comments and suggestions welcome.

[bojan]

Composite video can be combined by simple addition/dividing by 2, using fast operational amplifier, very easy to obtain, but for BW cameras only.
However, the cameras have to be in sync, both vertically and horizontally.
In case of colour cameras, the combining must be done on video part of the signal, so not to touch the colour burst and colour carrier. Attempt to combine BW and colour signal as described above may have quite unpredictable outcome, namely there will be some colour shift as a result of this operation, or the colour information may even be lost.
I am not sure how you can achieve all this with two simple CCD cameras, without sync and proper mixer, which disassembles the composite signal into components and then performs the addition to the relevant parts of the signal and then puts the whole thing back together again.. Actually I think this is not possible without extensive video stream processing, using powerful computer.

However professional cameras, much more expensive should be able to be synchronized. I am not sure of suitability of such cameras for Astronomy, though.

[ving]

sounds really interesting... let us know how kyou go.
i wonder what it will look like?

[Karls48]

Thanks Bojan
Yes that’s what I thought. Sync will be a problem. I may try to multiplex input signals then buffer it with opAmp.

[Karls48]

Hi Ving
Yes, I wonder what sort of image it would produce. I got two identical Mintron cameras but one is BW and other one colour. But it may prove impossible to combine two video signals in one on cheap.
Now, really stupid question. What about using binoviewer upside down with one camera only? I don’t have one and I’m only guessing how a binoviewer works.

[bojan]

This (binoviewer) may work in principle, but I think it is not worth the trouble (collimation will be the problem... you have to have it accurate down to a pixel size, 10 or so microns).
Just doubling the exposure time will produce the same effect as having double the light collecting area.
And, you are talking about composite video.. which means 25 frames per second (or 50 half-frames per second). That means the exposure time can not be longer than 20ms, so only bright objects - planets Moon, Sun will be accesible, but quite comfortably so.
BTW, BW camera will be more sensitive (due to lack of on-chip filters).
Just remove IR filter (most likely it is there) and you may be surpised with the increase in sensitivity (because of including IR part of the spectrum).
It may be better to invest in exploring possibilities to modify it for long exposures, to go into deep sky photography.

As I said before, to combine signals from two cameras will be very hard if not impossible (due to lack of access to required signals, to bring both cameras into synchronization). And, you will still need mixer, to add only video signals, and not to upset the rest of the composite videl signal (colour burst and color carrier, those will have to be regenerated for the combined video)
B

[Karls48]

Bojan, those Mintron cameras are very sensitive up to 0.0002 Lux in frame integration mode for BW camera and 0.008 Lux for Colour one. Camera integrates image for up to 2.56 seconds and then it refreshes the output. Of course it can be used to output AV stream at reduced sensitivity, 0.02 Lux for BW and 0.8 for colour one.
It also got S-Video output which if I remember correctly carries Sync signals on different pins for BW and colour.

[bojan]

If I were you, I would use one camera for imaging through one side of the binos, and use the other side for guiding with the second camera.
Also, I would investigate how to prolong the intergarting time...
I and would certainly abandon the ide a of combining the video streams, I do not believe there is any benefit in this approach...
B