I have to give credit for this discovery to "Photo444" and "DavidB in NM" who first suggested it in a post on the Cloudy Nights (CN) EAA forum in Jan 2015. You can find that discussion here.  I bought a board camera myself soon after the initial posts for only $23 from Securitycamera2000.com which included free shipping.  With it I built my own deep sky video camera for $35 which provides surprisingly good images.  ​    What is a board camera, you ask?  With video security camera use on the rise it is now possible to buy the electronic board which has the CCD, Digital Signal Processor (DSP), and other electronic components without the external housing at one-third to one-half the price of a low cost security camera.  You add your own custom housing and there you have a DIY camera ready for deep sky video.  The board camera pictured above shows the CDD, a 1/3" Sony ICX638 NTSC Super HAD II.  It has 768 x 494 effective pixels measuring 6.35 x 7.40 microns.  ​The reverse side of the board has an RJ10 Digital Signal Processor (DSP), 10bit A/D converter, additional electronic components and connectors for camera control, power and video output.

    The board camera comes with everything you need to build your own video camera except the enclosure.  Along with the 1.5" x 1.5" circuit board there is a 30" cable with connections for power (red) and video (yellow) and a 5 button in-line toggle switch to control the On Screen Display (OSD) for the camera's menu.  One end of the cable has connectors which attach to sockets on the back of the board for power, video and camera control.  The other end of the cable attaches to your video display (requires a BNC to RCA adapter) and 12VDC power (requires a 2.1 x 5.5mm power connection).  It also includes a CS Mount Base to attach a C-Mount adapter or focal reducer, an S Mount Base (also called M12 Mount)  to attach optional plastic wide angle lenses, two gaskets and some screws to attach the adapters to the board. 
    The first thing you will need to do is to remove the IR filter which is glued onto the front glass of the CCD.  This filter will block the all-important hydrogen alpha light from galaxies and nebulae if it is left in place making it much less sensitive.  Removing the filter requires heating the top of the IR filter with a soldering iron until the filter slides off.  The process will be easier if you hold the board in a vice.  I used a 40watt iron, others reported success with a 30watt iron.  The trick is to hold the barrel of the iron against the filter and not the tip as pictured.  It should take 20 - 30 seconds to free the filter.  I will admit, it took me several tries as I initially used the tip of the soldering iron, not the barrel.  I also tried to grip the filter with needle nose pliers and ended up cracking the filter.  None the less, I finally got the IR filter off without damaging the CCD.  Once removed, you will have some residual optical cement on the glass which covers the CCD.  This can be removed with a Q-tip and some alcohol.

    Next, you need to decide what type of enclosure to use for the camera.  In the CN link above, one person machined a very nice cylindrical enclosure made out of delrin.  Most, like myself, used a plastic hobby box.  I chose to use a 3" x 2" x 1" hobby box that I bought from Radio Shack for $3.80.  I drilled a 1" diameter hole in the center of the lid of the box to provide an opening for the CS Mount to fit through.  I also drilled 4 smaller holes centered on the 1" hole for screws to attach the board camera to the lid of the enclosure.  I made one last hole in the side of the box and added a rubber grommet for the cable to pass through.

    The next step is to attach the board to the front of the box.  For this, I used long screws through the front cover of the hobby box and through the 4 holes at the corners of the board. Nuts on both sides of the board were used to hold it in place and to get the desired spacing of the CCD from the front of the 1" opening.  After that, the CS Mount adapter needs to be attached to the board through the 1" opening using the included gasket and screws.  Then feed the through the opening in the side of the base of the box and connect the power and video wires to their respective connectors on the back of the board.  One of the three sets of wires will not be used as this is intended to control the Iris of a lens attached to the front of the camera which is not used for astronomy.  Once that is done, you can attach the top of the box with the included four screws.  Finally, I attached a C-Mount to 1.25" adapter to the CS mount and I was ready to go.  The final cost, including hardware to attach the camera to the box was just under $35.  Obviously, you can customize this any way you want.  One person even added a fan on the back of the hobby box to cool the CCD.  For most deep sky objects you will need a focal reducer which can be attached to the front of the 1.25" adapter.

   So how does the camera work? Surprisingly well.  I tried out the camera on the back of my 9.25" SCT with a 0.5X focal reducer that I bought on Ebay from China for $25 (which included a C-Mount to 1.25" adapter) for a focal length of f/5.  The images shown here are from my suburban backyard.  I was easily able to capture images of several galaxies (M51, M81, M82 and NGC2403) with exposures ranging from 8.5 to 17sec.  The maximum exposure for this camera is 17sec.  I also was able to capture images of M1 and NGC2024 (Flame Nebula)  with 17sec exposures.  M42 was even easier to capture because it is so bright that it only took 4.2sec to get a very colorful image.  To show how versatile the camera is, using a 2.5X Powermate from Televue, I was able to capture the Great Red Spot and bands of Jupiter with a 2ms exposure - I'm sure that if I captured and stacked multiple images it would look much, much better.
    I would say, for anyone who likes DIY projects and wants to try out video astronomy on the cheap, this would be the way to go.   The camera can be used to replace your EP, but it can also be used on a finder scope or even, as some have reported, as a guider.  Unfortunately, this particular board camera has been sold old and appears to no longer be available from SC2000.  However, AVS offers a version of this same board camera but with the addition of a second circuit board with power and video connectors along with some additional hardware for $39.99.  It can be found here:  http://www.astro-video.com/diy-camera-module-board.html.

In the meantime, keep looking on the CN forum for the next big discovery for DIY astro-video cameras.

    The adapter connects to the "Auto Iris" port on the back of the camera.  The receiver/transmitter portion of the BT adapter can be attached to the camera body with Velcro or an elastic band. ​  This is ideal for Hyperstar or Fastar applications on an SCT.  That way only the power and video out cables need to run across the field of view.  The picture below shows the BT cable dangling, but in actual use I secure it to the camera body so it does not block any incoming light. I do notice that in the Hyperstar position, the metal dew shield can reduce the effect range of the BT signal if the scope and camera are pointed away from me.

   I have used the Android application extensively on my Samsung Galaxy S4 phone and have found it to be much better than using a wired PC control.  The Android application was written by Charles C, who often posts on the EAA forum on Cloudy Nights.  It emulates the 5 buttons on the back of the camera, which means you will still need to see the On Screen Display (OSD) on your monitor to know where you are in the menu.  In addition, the MKIV application has sliders to control the Gain (this is not the AGC which must be controlled through the camera menu) and Brightness control sliders .  It also has a Freeze frame button and an Exit OSD button.  The DSO cameras do not have these additional function buttons since the camera firmware and hardware does not support these features.  The Exit OSD button allows one to save all the changes made in the camera menu and exit the OSD with the touch of a single button.  This eliminates the need to scroll down to the EXIT/RETURN/SAVE&EXIT command.   It also saves and exits without clearing the camera video memory, allowing operation to resume from where it left without interruption after changes were made.  Using the SAVE&EXIT command from inside the OSD "flushes all camera video memory buffers and may also trigger some protection circuitry , which leads to a white screen and having to wait for up to 3 minutes to fill up the video buffers again and display a new image".

    It is also possible to modify cameras like the Lntech 300 and Mallincam Micro to add BT capability.  You can read Charles C's post on CN here to find out how to make the modification.  Be forewarned, if you modify the camera you will void the manufacturer's warranty.