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Public Viewing With a Video Camera


I'm pretty much a regular at our Friday night public viewing sessions at Broemmelsiek Park.  During a long string of poor weather conditions during the winter and spring of 2011, I discovered and experimented with capturing deep sky objects with a low light security camera.  I've come to the conclusion that providing live video can be an important part of public viewing session.  Video will not replace eye piece viewing, but it can be very positive in a large group setting.  Video has the following benefits:
  • everyone in a party can see the same object at the same time
  • the party members can freely discuss the object on the screen
  • I can be sure everyone can see the image because I can point to it
  • less dead time vs. standing in line to view through an eyepiece
  • fainter detail can be captured/seen because of  extended integration times
  • objects can be seen around bright moon conditions 
  • color is more obvious vs. eyepiece views

While capturing images with a video camera won't compare with a good CCD or DSLR, it can give an eyepiece and small scope a run for the money.


(scroll down to the bottom of the page for actual pictures taken at Brommelsiek park with a SDC-435 and 160mm focal length zoom lens)

 

M42 taken with an SDC-435 from Steve Wainwright at http://astrovideography.blog.com/2010/10/   Check out his blog, he has tons of images taken with this video camera.
     
What can you expect?

One of the more difficult objects is always the Horse Head Nebula in Orion.  Below is one of my early attempts with the SDC-435 taken in early April of 2011.  The bright star is Alnitak.  The Horse Head can be seen as the dark patch towards the bottom left corner.  The image on the computer screen was much more obvious.

 
Both the Horse Head and Ring Nebula suffer from a number of issues including poor focus, hot pixels, exposure, and color.  My technique has improved as you will see below.
   
 
Below is a compressed 4 minute video taken of the Ring Nebula, M57 at the end of May of 2011.  The stars that move are stars (duh!). The stars that don't move are hot pixels.

M57


The parts:

     Necessary (see below for pictures, notes, and details)
  1. Samsung SDC-435 video camera  pixels 678(H) x 494(V) or other low light security camera that can record in very low light conditions.
  2. Power supply--AC adapter to provide 12v 500ma for Broemmelsiek and/or fused DC cord to provide 12v 500ma for field work
  3. 1.25" to C-mount lens adapter to use OTAs with focuser
  4. Frame grabber to get video to the computer
  5. OTA/Lenses (mine listed below.  Any will work if they are fast enough)
    • Celestron C-8 (must use focal reducer for DSOs)
    • Apogee 90mm f/6.1 refractor (should use focal reducer for DSOs)
    • Vicon 16-160mm f/1.8 zoom lens ($40 on EBay see bottom of the page for more information on possibilities with this lens)
    • Philips 12-240mm f/1.6 zoom lens  with 2x extender (see bottom of the page for more information on possibilites with this lens)
    • ETX-70
  6. BNC to RCA adapter and RCA cable (RadioShack)
  7. Computer for video display and capture or monitor for display
  8. Alt/Az or EQ mount

    Additions (add as needed depending on your hardware and location)
     
  9. Focal Reducer:  f/6.3, 0.5x, or Meade f/3.3
  10. Light pollution filter
  11. IR/UV filter (if you remove the stock filter)
  12. 2" nose piece to SCT for Meade f/3.3 FR
  13. T-mount to C-mount adapter for Meade f/3.3 FR
  14. Flip mirror
  15. various home made adapters to hold filters & focal reducers 




     

The bottom line is that it will probably run you about $200 to get into video via this route.

  Comments:

During the past year Samsung has renamed the camera SCB-2000.  You can still find online sources for the SDC-435 but check for the new name too. 

Nose pieces are also available for 2" to C-mount.

Video works best with more light.  Some people say the SDC-435 works best at focal ratios less than f/4 and I agree.  If your optics are slower than f/6 you will need to add a focal reducer to get good results with DSOs.  Longer focal lengths and larger focal ratios should give acceptable results with the moon and larger planets.

The SDC-435 has a 6mm chip (1/3").  Longer focal length optics will probably have difficulty seeing large DSOs.  A program like CCD Calculator should really help to give you an idea of what can be seen with your optics and a video camera.  See:  http://www.newastro.com/book_new/camera_app.php

Even a moderate telephoto DSLR or 35mm camera lens works well.  A 200mm focal length lens will capture a 76x57 arcminute field with the SDC-435's small chip.  In contrast, using a Celestron-8 with a Meade f/3.3 focal reducer captures a field of view of 25x19 arcminutes.  If you wish to use camera lenses rather than a telescope search for either C-mount, CS-mount, or CCTV lenses and you will probably be able to avoid adapters although you will need to play with the lens flange to sensor spacing. 

Adapting a zoom lens to the camera is an adventure.  Spacing between the lens flange and camera sensor is very critical if focus is to be held throughout the entire zoom range.  The spacing is adjusted by a combination of adding C-mount spacers and/or screwing the camera in/out from the lens.   Adjust the spacing to focus on a distant object at the shortest focal length with the lens racked in/set on infinity.  Slowly zoom to longer focal lengths and check the focus.  If the focus does not hold, return to the widest focal length and readjust.  This is DIFFICULT but rewarding because afterwards you have a digital zoom finder.  It makes finding and centering the object on the chip much easier.  This is an important concern when a line of people is forming during a public viewing session!

The Complete Package:
 
I'll take a picture and post it here sometime.

Notes and Details:

I'll first say that if you've never seen live video of DSOs you should probably take a visit to the Nightskynetwork at http://www.nightskiesnetwork.com/  On a dark night you may see up to twenty people broadcasting video of DSOs at the same time.  You'll either love it or hate it.  If you love it, you'll probably get into video.  If you have a way to connect to the Internet at your observing site you'll probably broadcast at some point.

Surfing around the Internet in the fall of 2010, I found some references to Samsung's SDC-435 low light security camera (Google it to see actual deep sky pictures).  I noticed some interesting images and comments about how well it performs... up to 8.4 second integration at 0.0001 lux.  I can't afford a Mallicam (the Cadillac of astronomy video), but I did notice some of the people on the Nightskynetwork did use the 435.  Doing a quick check of prices I found that it was in the affordable range and  I took the plunge and ordered the 12v NTCS version from buy.com about $135 with free shipping.  It arrived in 3 days.  There is a guy who sells from Korea for slightly less, but it will obviously take longer to arrive.

Inside the box were four things (notice no power source or lens provided):

  1. the video camera (tiny little thing) with a c-mount lens adapter,
  2. CS-mount lens adapter (really just a spacer),
  3. rubber body cap,
  4. instruction manual (see: http://www.eposcctv.com/manuals/EPOS%20CCTV%20SDC-435.pdf).

The camera produces a video out signal via a BNC connector.  The video can be displayed on a monitor or computer if a frame grabber is available.  Software can either display the video on a computer screen, record individual frames or record video. 

Like most cameras there is an IR filter that covers the sensor and like most filters it cuts of the light produced by the Hydrogen alpha line.  Do take the time to remove your filter. I did.  Unlike DSLRs, the filter is quickly and easily removed.  If you do remove the filter, do use a new IR/UV filter like Baader's that passes the light from the Hydrogen alpha line.  Join the Yahoo SDC-435 group to see filter removal directions.

The camera is adjusted by pressing the five buttons (up/down/right/left/set) on the back (see picture).  It does cause the image to "jump" on the computer screen.   You can find soldering modification on the Internet that move the buttons to an external box.  I'm not brave enough to do that mod.

While there is some debate as to how much cooling helps with the 435, I opted to drill a few holes in the top and add a cooling fan to pull air through the camera body.  I've also added a male/female plug to supply power rather than just screw the 12v wall wart to the power terminals.

 

 
front of camera
                                         rear of camera

SDC-435 Sensor and IR filter



From the various online reports, CNs, and the SDC 435 Yahoo group, I knew I'd need to put some parts together to make the whole thing work.  The first part of the puzzle would be a AC power supply since there is no supply with the video camera. I got a 12v 500ma wall wart plug type from EBay for $10 and shipping.  

It should be possible to power the camera via a 12v battery because it doesn't draw much power.

 


110V AC

Since my net book has no video-in I knew I would need a frame grabber.  A frame grabber can display video from the video camera on the net book's screen and make the video signal available for capture. Many of the 435 users recommend a Dazzle.   Mine is a Dazzle 100 DVD.  You will need video capture software.   The free program wxAstroCapture works well.  If you plan on trying to do astrophotography with the camera it might be a good idea to find a program that lets you set the frame capture rate to 2, 4, or 8 seconds.  Consider, if you are integrating at the highest sens-up of x512 you get an updated frame every 8.5 seconds.  There isn't much purpose in recording 30 frames per second if you only get a new one every 8.5.  It will help keep the file size down.  Your software should also have provisions for dark frame and flat subtraction.







A second option would be to use a video monitor for output.  It would limit your output to viewing only vs being able to record and save using a frame grabber and computer.  On nights that I don't want to record I use a Haier a flat screen LCD 7" monitor.  Since it was designed for video input it seems more responsive than the frame grabber/computer route.  It is also easier to set up, requires less hardware, has an internal battery that gives about two hours of viewing time, and does have a remote control for adjustment.  The only drawback is that so far I have not found a way to get the background sky dark enough for my taste using the monitor.
 
 
 


Dazzle 100 DVD

Haier 7" LCD flat screen monitor

As you can see in the pictures, the SDC-435 has a BNC video out while the Dazzle and Haier monitor have an RCA video in.  The next thing I needed was a BNC to RCA adapter for the back of the camera so I could use an RCA cable to get the video from the camera to the frame grabber.  A 3 foot RCA cable works fine since the Dazzle has a 6' USB cable to get the signal to my laptop but I use a 6 foot RCA cable when going to the Haier.
 
RadioShack usually stocks these adapter.  They are really cheap so get two, you'll loose one.
   
BNC to RCA Adapter

The next problem to solve would be connecting the video camera to my telescope.  I found a 1.25" to C-mount adapter at eBay for $20.  It screws into the C-mount on the video camera.  It is plastic so I hope there are no disasters in the future there.  It does have threads on the 1.25" side to mate filters or a focal reducer, so that's a plus.  It just happens to the correct length for the required spacing with my 0.5x focal reducer...double plus!

I later found Agena Astro has the nosepiece in metal.  It helps remove heat that eventually leads to amp glow.

While a 2" nosepiece is available, it and the filters would cost much more than one for 1.25".  Since vignetting won't be a problem with the tiny 6mm chip, I opted for the 1.25" route.


Lately I've been using a flip mirror between the OTA and the Apogee.  One end of the flip mirror has a 2" focuser tube and the other has a T-mount thread.  As a result I connect the SDC-435 to the flip mirror with a T-mount to C-mount adapter.  There is enough room inside the adapter and back of the flip mirror to hold both a .5x focal reducer and Baader SemiAPO filter.  I use an old 40mm eyepiece in the flip mirror as a wide field finder in case slews are not spot on.  The combination helps although in focus was a problem for a while until I made a holder that fit inside the flip mirror.

 

 

1.25" to C-mount nose piece

     

You might think that you need a equatorial mount since you are dealing with a camera and photography.  This isn't really necessary since the maximum integration time is 8.5 seconds.  Alt/Az works just fine.  If you do try imaging with the 435 you'll eliminate field rotation by using DeepSkyStacker since it can correct for rotation.

It is possible to connect various DSLR lenses to the SDC-435 with an adapter.  Adorama has a variety of these adapters like a Canon FD or EOS to C-mount adapter for my old Canon FD lenses or newer EOS ones.  For what's it's worth, my old Vivitar 400mm f/6.3 lens covers about 1 degree field when coupled to the SDC-435.

It is possible to rig an adapter that fits inside to hold a 1.25" IR and light pollution filter. 

I'll also point out that there is an adapter that will let you mount board camera lenses (M12 mount??)  like you see on webcams.  It is just a metal disc with c-mount threads on the outside and a hole with the lens threads on the inside.  You won't find any board lenses in longer focal lengths, but if you are interested in wider field work it certainly is a option.  As with a webcam you focus these lenses by screwing in/out until best focus is achieved. 

If you have an interest in AllSky cameras you can get a board camera 2.1mm or wider (1.8mm) fisheye lens and mount it on the 435 (search eBay for 2.1mm lens). You should get almost the entire sky in the frame.  It should produce really interesting results during meteor showers or of the entire sky.  An acrylic dome may prevent dew.


I'm pretty sure there is an adapter out there that will connect the SDC-435 to most  OTAs, current brands and many of the popular older lenses.  I do have a number of medium format Kowa lenses that I don't think that I can find an adapter for but prowling around ebay for C-mount adapter should give plenty of options.  Once you find an adapter you can get older 35mm lenses that should work.


   

Adorama EOS to C-mount adapter

M12 to C-mount adapter

A Note About Focal Length:
 
You might notice from both above and pictures below that one of the lenses I frequently use is a Vicon 16-160mm f/1.8 lens that I got on eBay for a song.  You might think that with a maximum focal length of 160mm it would be much too short to use for any kind of astronomical work, after all a Celestron 8 has a focal length of over 2000mm.  In fact, nothing could be further from the truth.
 
The sensor in the SDC-435 is described as a 6mm chip.  That means it is 6mm diagonally and as such, it is very small.  The small size of the chip means that you don't need a very long focal length lens to get a reasonably small field of view.  The 160mm focal length of the Vicon gives a FOV of 77.5x103.4 arc minutes, which works pretty well with the larger Messier objects.  Using a  2x teleconverter on the  Vicon lens lets me cut the FOV to half that, but adds coma and  makes the objects dimmer.
 
Since the chip is so small GOTOs must be spot on or you may have trouble locating the object on the sensor.  Depending on which lens/camera combination I use I have resorted to swapping the camera with a long fl parafocalized eyepiece, using a flip mirror, or using the zoom feature on the Vicon to center the object in the field after slews.  Each of these options has drawbacks:  back focus problems with optics, inability to use filters or FRs, and spacing of optics.  Nothing is every easy!
   A Note About Aperture:

The more light the better.  In one post, the author suggested at least four times that you needed to be at f/3 or faster for DSOs.  I don't know if it is absolutely necessary, since I've used my Apogee f/6.1, but my C8 at f/11 won't cut it without a .5x focal reducer. 

Faster is better.


A Note About Field of View 

Before you jump in with both feet and a credit card you might want to first download and play with CCD Calculator  a free program that will let you visually explore the field of view with various optical tubes/lenses/camera/barlow/focal reducer combinations.  There are many built-in optical tubes and it is easy to add additional cameras and lenses. 

If you wish to enter the 435 in CCD Calculator it will help to know that the  pixel size on the 435 is 6.35x7.4 and the array size is 768x494.   You will soon discover that it doesn't take much focal length to fill the 435's sensor with a DSO.

     
Settings:

One of the more challenging features of using the camera is adjusting the settings in the following  eight areas.  Use the following as a starting point for your work.  See the SDC-435's documentation for further details.

   
    
Lens
 
  • Set to manual when attached to optical tube
     Exposure

Brightness
Shutter


AGC
Sens-up
   
  • Set to 1
  • Set to Manual and select the shutter speed here 256x is 4.2 seconds.  You may need to adjust the shutter speed for each object you view for best results.  You will change this setting often!
  • Set AGC to low or high (automatic gain control)
  • Off (use the shutter above to set the shutter speed--1/120,000 to 8.4 seconds. 
    (Sutter speeds like x512 are approximately 512/60 or 8.5 seconds)
    
White Balance
 
  • ATW if stock IR filter is in place, Manual if you remove the IR filter and adjust for best results

     SSDR
 
  • Samsung Super Dynamic Range OFF
    
Backlight
 
  • Off
 
    SSNR3
 
  • Noise reduction ON
    
Day/Night
 
  • Color
   
 Special
 
  • Under Monitor set LCD or User
  • Adjust horizontal and/or vertical flip as needed
In addition, you will need to use the dialog with the frame grabber to set the video mode, contrast, gamma, brightness, and saturation.  These setting are accessed via menus in the screen capture software you choose to use.  As a result each will be somewhat different until the actual driver dialogs are accessed. 

I usually use the capture program's contrast and brightness adjustments to set the dark and white points.  Having capture software that provides a histogram is helpful. I've already mentioned that I like the free wxAstroCapture.  HandyAVI ($) also works well.  I have started using DeepSkyImaging to display and capture images.

 

 

  Your frame grabber may have video modes with more resolution than the camera can provide.  You will probably want to set the video to NTSC-M.

When looking for capture software a nice feature is the ability to zoom the image so that it fills the computer screen.

If you record video or take screen shots do make sure you know where the files are saved and that the software automatically generates different names for each file or older pictures/video isn't overwritten.
What kind of results can I expect:
 

M27















  • Apogee 550mm FL with .5x FR for FOV 46x61 arcminutes for 275mm @ f/3
  • 100 bmps stacked with Deep Sky Stacker
  • Integration 512x (8.4 seconds)
  •  
    M57















    • Apogee 550 FL with .5x FR for FOV 46x61 arcminutes for 275mm @f/3
    • 100 bmps stacked with Deep Sky Stacker
    • Integration 512x (8.4 seconds)

    M6 Vicon
    • Vicon Lens @ 160mm and f/1.8 for a  FOV 77.5x103.4 arcminutes
    • Focus with Bhatinov mask on computer screen using a bright star (Antares)
    • Integration 256x (4.2 seconds)
    • Single shot screen grab
    • No filter, stacking, or processing
    • Taken at new moon
       M7 Vicon(see left for data)
     M8 Vicon(see above for data)

       M8 Apogee(see above for data)

     M11 Vicon(see above for data)

       M13 Vicon(see above for data)

     M16 Vicon(see above for data)

       M17 Vicon(see above for data)

     M20 Vicon(see above for data)

       M20 Apogee(see above for data)

     
    M22 Vicon(see above for data)
       
    M81 and M82
    Vicon (see above for data)

         
    Can the SDC-435 be used for astrophotography?   Yes, but as you can see, a CCD or DSLR will produce much better results.  The actual pixel size of the image is very low, typically 720x480 or less.  Using 2x or 3x drizzle processing can help increase resolution.  It is possible to take flats and darks.  However AGC may do strange things to the darks. 

    Grabbing individual frames is a very easy way to record an image for later review or proof of object.

    You will notice lens aberrations if you use a focal reducer and the spacing isn't correct.

    Can the SDC-435 be used as an auto guiding camera?   I have yet to try, but PHD does recognize the camera, so my best guess is that it would do well.



    Are there any idiosyncrasies?
     


    When using long integration times it takes a while for the screen to update.  When slewing from one object to another bright areas in the first image take a while to disappear from the screen, sometimes obscuring the second object for a while.  It may take a minute or so for the second object to be fully revealed.  You erase the old image faster  by going into the menu and reducing the exposure time to about x16 and then stepping back up to the longer integration time, but it takes almost as long as letting it sit and the "dissove" to new image is kind of fun to watch.

    Some times changing the shutter speed too quickly "locks" the camera.  Change the shutter speed to a much faster setting and slowly change the speed to slower usually corrects the problem.

    Hot pixels will appear as the camera gets warmer or older.  Stacking software may think that they are stars and produce strange results.

    Amp glow will slowly build as the night progresses.  You probably won't notice it on the computer screen, but if you record video, you'll probably have to deal with it.  Taking darks should help.

    Unless your mount is much more solid than mine, pressing the controls on the camera will cause the image to shake for some time.

    I've mentioned that the 6mm chip is pretty small.  Unless your GOTOs are spot on, you may have a bit of difficulty locating the DSO in the camera's field.  Swapping the camera for a parafocalized longer focal length eyepiece or using a flip mirror can really help locate and center the object. 

    While on the subject of small chip, if your mount suffers from drift from poor alignment or periodic error, you'll notice the object wandering in the field.

    Looking at the computer screen all night does kill night vision pretty well even when you cover it with rubylith.  Curb your excitement when you see a particularly difficult object like the Horse Head Nebula, the visual observers will want to see, but then complain about you destroying their night vision.

     Conclusions:  
    Providing live video can be an important part of public viewing session.  Video will not replace eye piece viewing, but it can be very positive in a large group setting. 

    Video has the following benefits:
    • everyone in a party can see the same object at the same time
    • the party members can freely discuss the object on the screen
    • I can be sure everyone can see the image because I can point to it
    • less dead time vs. standing in line to view through an eyepiece
    • fainter detail can be captured because of  extended integration times
    • objects can be seen around bright moon conditions 
    • color is more obvious vs. eyepiece view
    • visually challenged have a better chance of seeing
     

    Final Comments and Thoughts:

     

    A beginning video setup is much less ($) than a good eyepiece, although I'd guess that it won't last nearly as long.  Video is still in it's infancy and as time passes technology will improve even more.  In a few years we should see cheaper, bigger, more sensitive chips that can record even fainter objects and detail.  Someday I suspect that new telescopes will come with video cameras and not eyepieces.  There are interesting threads at Cloudy Nights predicting the future of telescopes, viewing, video and such over the next 30 years.  This is one of the predicted trends.
     
     If you are in the St. Louis area and interested in live video demo maybe we can meet at Broemmelsiek sometime.  Drop me a line and I'll see you there.





    Vicon Lens:

     
    I noticed in some Cloudy Night posts that one of the SDC-435's early supporters, scout72, sometimes used a really large video camera lens rather than a traditional OTA.  Looking at various eBay searches with "CCTV, TV, zoom, c-mount, and lens" revealed very interesting lens combinations of  focal length and aperture.  As mentioned above I pounced on a 16-160mm f/1.8 CCTV c-mount zoom lens for experimentation (remember the SDC-435 is a c-mount camera).  Once I figured how to set the flange/sensor spacing to the correct distance, and make some spacers, the lens produced pretty good results.  As an added benefit it also can act as it's own finder at wider zoom focal lengths.
     
    Many of the TV/CCTV zoom lenses are electronic focusing and zoom and the Vicon was no exception.  I had to make a control box to zoom and focus the lens.  A DPDT switch for each, a common push button, a 9v battery, and a RadioShack project box.  One of my major difficulties with the Vicon lens was getting spot on focus via the push button to control the motors inside the housing.  No matter how much I tried, it seemed like I'd always slide past the best point.  As a lark, I removed the housing and to my surprise, I found what I would call a traditional lens with a focus, zoom, and aperture scale and adjustment rings.  For the time being I'm leaving the housing off and plan to do all focusing and zoom manually.  An added benefit is that prior to removal of the housing the camera was actually too sensitive to light to be able to capture moon images under more than 1/4 moon conditions.  Removing the housing also gives access to the aperture ring and now the full moon is possible.
     
       


    Vicon lens as purchased:               




    Vicon lens without housing:


    C-mount 2x extender:
    While the 160mm maximum zoom is good for larger DSOs, smaller objects were pretty small.  I smile when I think of the night I scanned my computer screen for M57 for minutes before I finally saw the tiny dot in the center of the screen.  Once again prowling eBay, I discovered that a 2x telextender for c-mount exists, and I purchased one to see how it would work with the Vicon lens.  Telextenders never improve an image but based on the fact that I'm only capturing 740x480, I don't need the sharpest optics and I think the combination produces positive results.  The telextender should give a 32-320mm @ f/3.6 lens producing a 38.7x 51.7 arc minute field of view if CCD Calculator is correct. I do get sharper and better corrected images with the Apogee refractor because I can use a SemiAPO filter in the light path, but it is fun to see the look on faces when they realize that I'm using a complete video rig.





    Philips Lens:

    Just before Christmas 2011 I found a C-mount Philips 12-240mm f/1.6 auto-iris zoom lens for sale on eBay for 99 £ and did some checking.  CCD Calculator shows that the lens should deliver a field of view that is 26.1 x 34.9 arcminutes with the 2x extender at f/3.2 at the maximum zoom.    The lens should give about the same field of view as my C-8 with a 15mm eyepiece.

    I took the plunge and the lens arrived from Manchester,  England in a week.   The way the lens was packed made it look like it had never been used.  Some soldering produced an external zoom & focus box that works well.  Coupling the lens with the SDC-435s extra CS mount spacer,  focus & zoom that were almost perfect throughout the entire zoom range without any additional spacing.  Supplying  the lens with 12V and ground, and leaving the video open defeated the auto-iris so it is now manually adjustable, a plus.

    I wasn't able to get the Vicon lens spaced well enough for the focus to be preserved throughout the zoom range.  Since the Philips stays in focus, I now have a lens that can serve as its own finder...zoom out to locate and center object, zoom in to view in good detail.  Now all I need to do is get  some good weather and go out observing.
       Phillips Lens as purchased:
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