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astrotrf
professor emeritus
Reged: 09/30/07
Posts: 703
Loc: Rodeo, NM
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Well, maybe not quite so "remote", but still ...
I run the scope and camera in my rolloff observatory sight-unseen from my basement, and that's all well and good, mostly -- but every once in a while I am seized with the need to see exactly where my scope is going during a goto. And I'd also like to be able to close the roof from the basement, so I *really* need to see the scope to make sure it is in a safely-parked position.
So I have my eye on an ultra-low-light-level video camera, which I'm hoping will be able to give me a useable view of the interior at night. But, of course, *that* led to the idea of a *second* camera pointed at the night sky, probably more for fun than any useful purpose.
I sort-of planned for this, by running a single RG-6 cable from the observatory to the basement control area. But I'm kind of stuck there. I don't know exactly what the output of the video camera is, but I'm guessing it's a BNC connector. Can I just use an adapter to connect that to my RG-6 line and then a second adapter to connect the RG-6 to a security monitor? And that may work for *one* camera, but how can I multiplex *two* cameras onto my single cable?
If anyone knows what I need to do, I'd sure appreciate some advice.
Thanks.
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Terry (astrotrf)
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GrampianStars
member
Reged: 07/15/04
Posts: 28
Loc: Grampians, Australia
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Terry
Take a look here for ideas 
http://tech.groups.yahoo.com/group/Open_Observatory_Control_System/
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Robert
37° 11' 32.5" Sth 142° 36' 45.5" Est
LX200 GPS12-Mity Wedge-GPDX-SS2K-ED80-ZS80
CDK17 wannabe
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StarmanDan
sage
Reged: 08/27/07
Posts: 391
Loc: China Spring, Texas
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You sort of answered your own question. You could get a multiplexer which would allow you to combine multiple camera feeds into one giving you a split screen view of all the cameras. New, a basic four camera B&W multiplexer will set you back about $100.
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"Starman" Dan Doyle
Texas Astronomical Society of Dallas
Central Texas Astronomical Society
8" LX200GPS w/ST80 guidescope, Canon 350D+DSI Pro
150mm f/8 Sky Watcher Refractor
10" f/4.5 Homemade Dob
RV-6 Criterion Dynascope
http://darcstar.wordpress.com
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astrotrf
professor emeritus
Reged: 09/30/07
Posts: 703
Loc: Rodeo, NM
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Robert,
Thanks for the link. I scanned the subjects, but didn't find anything obviously about remote video monitoring. But I need to read that whole thing; I can write code and may be able to offer my help.
Starman,
So the idea would be to buy one of these multiplexers, connect both cameras to it, and then feed the output of the multiplexer down to the basement via my RG-6 cable, I take it.
But the multiplexer output will be BNC also, correct? Can I just use a simple connector adapter to attach that to the RG-6? Will there be enough signal strength to travel down, say, 100' of RG-6? And what it will look like on my security monitor is that each camera will occupy 1/4 of the screen, correct? So for my 2-camera setup, half the screen would always be blank (OTOH, I'd have some expansion possibilities ...). I'd need a bigger monitor; I only have a little 10" job.
It'd be handy if there was a small box that would turn the camera feed into TV channel 3 or channel 4. Then I could feed those channels down the cable and use a regular TV to view the scenes by switching channels.
Which leads to another question: can I use a simple connector adapter to turn the BNC output into an RCA composite video, so I can plug it into an old VCR (which would in turn output channel 3 or channel 4)? I could then solve the problem with a pair of junker VCRs.
Thanks for any additional ideas.
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Terry (astrotrf)
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astrotrf
professor emeritus
Reged: 09/30/07
Posts: 703
Loc: Rodeo, NM
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I think I've got this figured out. I finally stumbled on a web site that leaked the top-secret information that a "video modulator" is what they call a device that turns composite video into a TV channel. The second hard-to-find bit of information is that the BNC output of a security camera is, in fact, composite video.
So I just need a pair of video modulators, set to output different channels, and combine their outputs onto the RG-6 cable, then feed that to the external antenna input on a regular TV. The BNC output of the cameras converts with an inexpensive (87 cents at one site) connector adapter to an RCA female, and a standard RCA composite video cable connects to the video modulator.
Half of the problem is just learning what folks "call" things; the other half is finding a web site that gives actual technical information instead of baby talk.
Thanks for the help; it finally got me going in the right direction!
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Terry (astrotrf)
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ADeane
member
Reged: 10/12/08
Posts: 42
Loc: South West Ontario
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The output of the camera will most likely by a BNC connector. You can purchase twist on BNC to RG6 connectors for the camera end. The video provided is composite video, the same as any yellow output from a VCR, DVD ... If your TV has multiple Video inputs, you can select between Video1, Video2 and therefore don't need the modulator or a multiplexer and it will be better quality video than the modulated channelX. Consider cameras with infrard detection and their low light capability is GREATLY enhanced. Another consideration is you'll need power to each camera, typical 12vdc or 24vac. If you run the video through a VCR (if you can still find one LOL) you can record what's going in if you ever need to.
Andy
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Rondeau Provincial Park
Skywatcher 8" Collapsible Dob
Bushnell Legacy 10 X 50 Bino's
Meade 60mm Refractor (junk!)
Nikon D5000 w/ 18-55mm & 55-200mm zoom
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astrotrf
professor emeritus
Reged: 09/30/07
Posts: 703
Loc: Rodeo, NM
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Thanks, Andy, for the info.
Quote:
If your TV has multiple Video inputs, you can select between Video 1, Video2 and therefore don't need the modulator or a multiplexer ...
Well, I have only a single RG6 cable from the observatory to the control room, and it has to carry both camera signals. So I think I'm stuck modulating the cameras onto separate TV channels, unless there's something else I don't know about.
I've scrapped several junker VCRs; wish I'd'a kept 'em now ...
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Terry (astrotrf)
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StarmanDan
sage
Reged: 08/27/07
Posts: 391
Loc: China Spring, Texas
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If your intent is to be able to see each camera "full screen" on the TV, then you will need to modulate each camera on its own channel. The multiplexor will also do full screen viewing, but you would need to figure a way to remotely control the multiplexor as it would be attached to the camera side of the RG6 cable.
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"Starman" Dan Doyle
Texas Astronomical Society of Dallas
Central Texas Astronomical Society
8" LX200GPS w/ST80 guidescope, Canon 350D+DSI Pro
150mm f/8 Sky Watcher Refractor
10" f/4.5 Homemade Dob
RV-6 Criterion Dynascope
http://darcstar.wordpress.com
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astrotrf
professor emeritus
Reged: 09/30/07
Posts: 703
Loc: Rodeo, NM
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Thanks, Dan. I've ordered a pair of cameras and modulators that can be set to channel 3 or 4.
Thanks to all for the assist!
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Terry (astrotrf)
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Fish
sage
Reged: 10/13/07
Posts: 470
Loc: Norridgewock, ME
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Terry,
You're on the right track with modulators, doing essentially what cable companies do. But beware: Channel 3 has a video carrier of 61.25 Mc and channel 4 at 67.25 Mc. In commercial analog TV a (vestigial) sideband filter was used to cut off a good deal of the lower sideband energy - it was a AM transmission - to reduce adjacent channel interference.
Most consumer modulators do not include LSB suppression - it was external to most TV transmitters as well - so you may get noise from one channel getting into another. You might want to find a channel 2 (55.25 Mc) to go with the channel 4 one or, better yet, a channel 5 (77.25 Mc) one to use with either 3 or 4.
Cable supply houses have these, along with channel pass and reject filters. If you get it right you will have little if any problems but getting channels 3 & 4 to mix cleanly could be challenging.
Regards, Marc
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Goseck Observatory
Kunming 152 f/5.9 & Baader Wedge
Orion ED80 & LS75FHa2/B1200
Meade 102ED & LS18CaKMDd2
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astrotrf
professor emeritus
Reged: 09/30/07
Posts: 703
Loc: Rodeo, NM
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Marc,
Thanks for the heads-up on the possibility of interference. I admit that I was a bit concerned from the outset about using adjacent channels ...
I'm going to try what I have to see what it looks like -- but at least my expectations are now correctly set!
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Terry (astrotrf)
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StarmanDan
sage
Reged: 08/27/07
Posts: 391
Loc: China Spring, Texas
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If you look around you can probably find a modulator that can do any channel in the UHF/VHF band.
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"Starman" Dan Doyle
Texas Astronomical Society of Dallas
Central Texas Astronomical Society
8" LX200GPS w/ST80 guidescope, Canon 350D+DSI Pro
150mm f/8 Sky Watcher Refractor
10" f/4.5 Homemade Dob
RV-6 Criterion Dynascope
http://darcstar.wordpress.com
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