Orion Skyquest XT10i Intelliscope Newtonian Reflector Telescope on Dobsonian Mount
A close encounter with the Orion XT10i Newtonian Dob with Intelliscope Object Locator
Astrophotography with an SCP900NC WebcamHere are some pics and comments about my Philips SPC900NC Webcam which I use to capture pictures and movie footage for astrophotography in conjunction with my Orion Skyquest XT10 Intelliscope newtonian reflector telescope.
Not all webcams are made equal.
For a webcam to be suitable for astrophotography it needs to be particularly sensitive to light. Webcams with CCD (Charge Coupled Device) chips are generally more sensitive than CMOS (Complementary Metal Oxide Semiconductor) chips, certainly in webcams, although some more recent makes of CMOS chips used in professional DSLR cameras are able to offer the required light capturing ability.
Generally if you are searching out a webcam for use with a telescope, try to find a CCD webcam, otherwise be sure that any CMOS webcam is sufficiently sensitive and has been tried by other astonomers. The Toucam Pro I and II models were the original favourite choice for astronomers.
The SPC900NC uses the Sony ICX098QB CCD sensor. As I understand, the SPC900NC is now a discontinued model, but I was able to purchase mine from a supplier through EBay. Beware that more recent models of Philips webcams use a CMOS chip and may not be as sensitive as the CCD.
Generally cheap webcams do not offer high resolutions for movie capture, the norm for affordable webcams being 640x480, or 1024x768. Anything greater than this generally starts to get more expensive.
The webcam software (and/or driver software) should also be able to control the Exposure and Gain, and additionally helpful is Brightness, Contrast, Colour or Black & White options. There may also be other options for special features or capabilities specific to that model of webcam which may be useful to control the quality of astro photos.
Most webcams are used for capturing movie at 5, 10, 15, 24, etc FPS (frames per second), or for taking single shot photos of brightly lit objects with short exposure times of anything from a few thousandths, hundredths of a second to 1/4 or 1/2 a second. Generally the moon, planets and similar bright celestial objects can be captured and enhanced using software such as Registax or K3CCDTools, which will align the many frames of movie footage exactly over each other, then stack them together, then sum all the frames into a single enhanced composite image which is far brighter, sharper and clearer than any single frame would have been.
But to take single shots of dim night-time objects like stars, galaxies and nebulae requires the webcam to be capable of taking very long exposures, more like 5, 10, 30 seconds or even longer, sometimes 5 minutes, 30 minutes or an hour long!
One of the prime reasons for me searching out this particular webcam was because after considerable research on the Steve Chambers (SC) Long Exposure mod, not only was the SPC900NC webcam still fairly readily available, and used a good sensitive CCD sensor chip, it also became apparent that the Long Exposure modification could be made much more easily than for some other webcam models, which require some very fiddly soldering (see Useful Resources section below for link to M.M.J.Meijer's web site, for more info on how to actually make the Long Exposure mod). While I realise that my Orion XT10 on its standard Dobsonian base won't be any use for long exposures, I wanted a webcam that could be modified, if and when I get another telescope / mount that is more suited to deep-sky astrophotography.
There are two main problems regarding long exposures:-
While point 2 can be dealt with using software to create a "dark frame map", which is then subtracted by post-processing the image, point 1 is absolutely crucial and means that Dobsonian mounted telescopes such as the Orion Skyquest range are simply incapable of taking long exposure photos, unless the Optical Tube is mounted on an Equatorial tripod, or the Dobsonian is modified to sit on an equatorially tracking platform, or the Altitude and Azimuth axis' are motorised.
To combat the heat problems described in point 2 above, it is possible to attach heatsinks to the imaging chip, and use fans to aid cooling. Additionally a special type of semiconductor called a Peltier chip is used in conjunction with a heatsink to act as a kind of "refrigerator" to cool the imaging chip down even more, often to temperatures well below freezing. For example Peltier chips are used in portable coolboxes to keep food and beer cold.
All these different things (cooling, heatsinks, fans, peltier chips, high resolutions, and better quality imaging chips) soon add to the expense of professionally manufactured astronomy cameras, and this is why some of them can cost hundreds or thousands of dollars!
Note that there is probably no point in making the Long Exposure mod to your webcam unless your scope has Equatorial tracking.
Anyway, for the paupers, newbies and experimentalists among us we can try our hand with a cheap webcam.
It is possible to get reasonable pictures of the planets even with a Dobsonian mounted scope, using the Field of View Drift method, as I call it. You line up the planet in one corner of the webcam screen view, then let go, leaving the scope static, and let the planet drift diagonally across the field of view as the Earth rotates, roughly to the opposite corner. With my Orion XT10, and just the webcam in place at prime focus (and no Barlow lens to increase magnification) the drift takes betwen 30-40 seconds.
This means a webcam movie capture of 10 FPS will result in about 300 to 400 frames which can be aligned, stacked and enhanced.
Golden Rule: Remember when capturing movie footage, that it is always better to under-expose, or reduce the gain of the webcam for a particular planet, i.e. deliberately give a dimmer picture, because the post-processing will tease out and brighten the imagea, and subtle details are better obtained like this than if the original image is too bright and washed out.
This is my Philips SPC900NC Webcam. The front lens can be rotated to focus the camera. Unfortunately it also has a nasty bright white LED lamp to kindly indicate when the camera is functioning (any kind of bright light is not good for dark-adapted eyesight!).
Note: I recommend you become familiar with the operation of the webcam and its software under normal conditions before you start dismantling it, because after removing the original lens you will not be able to focus the image unless you put it into your telescope.
Using the flat edge of a screwdriver gently prise the focuser up and out of the camera body. Try to ease the clips out evenly all round. Getting the clips to release is quite hard, so be careful not to break any of the three plastic lugs which clip the focuser into the camera body and hold it in place, so that you can continue to use the webcam for its normal function if you wish.
Here is the lens and focuser after removing from the body.
The shot below shows the focuser removed, but the lens still screwed in place. Just unscrew the lens anti-clockwise until the lens comes right out.
The lens unit incorporates the lens and an infra-red filter, but we will no longer use this for astrophotography. Keep it, and the focuser, somewhere safe so that you can use the webcam normally again in future if you wish.
Once the lens is removed you can see the CCD chip. Do not leave the chip uncovered for long - you don't want any dust particles getting onto the clear face of the chip as they may become visible on any photographs you take.
The next thing to do is to replace the normal webcam lens with a 1.25 inch barrel adaptor. This will screw snugly into the webcam body, in place of the original lens, and the barrel is the correct diameter to fit into the eyepiece holder of your telescope. The adaptor should also be "baffled" inside to help reduce light reflections (this is a kind of stepped feature within the adaptor nozzle).
When purchasing the adaptor be sure to get the correct type. The first one I ordered was almost right, but the screw thread was not long enough to locate into the thread within the camera body, I think it was from an old batch or was for an earlier model of the SPC900NC. The supplier soon replaced my order with the correct part. Also be careful when inserting the adaptor into the webcam that you do not overtighten it or the nozzle might hit the CCD chip and damage the clear face of the chip.
The UK supplier I used was Scopes-N-Skies, and the exact part I ordered was the AC414n 1.25" Nosepiece Adaptor.
The front end of the adaptor is also threaded to accept filters. So in addition to purchasing the adaptor, I also ordered an Infra-Red & Ultra-Violet Filter to screw into place. Here is the webcam plus adaptor, with the IR/UV Filter on the desk.
Again, Scopes-N-Skies were able to supply the filter, which was the AC582 1.25” Infrared & UV block filter for web-cam and CCD imaging.
So here is the webcam ready for use with the telescope. You can see the baffled anti-reflection feature within the adaptor.
I would also suggest you also take a look at Robert Reeves SPC900NC Webcam page showing some additional photos of this webcam, and describing in more detail how to dismantle the unit.
Make things easy to start with.
First, during the daytime, install the software that came with the webcam, and become familiar with its various functions, features and settings. Its best to do this before you replace the original lens with the eyepiece adaptor.
The software supplied is VLounge. While VLounge is ok for getting started with taking astrophotography footage, it is better to use software dedicated to the purpose. K3CCDTools is specifically written for this job, and is also programmed to control webcams that have the Long Exposure mod.
First try experimenting with the settings, in particular the Exposure and Gain settings. Have a go in a darkened, dimly lit room, pointing the webcam at something and making sure it is focused. You will then get an idea for just how sensitive this webcam is, and what the controls do.
When you plan to try the webcam with the telescope, be organised about it. Here are some tips:-
Video & snapshot capturing:
| Max. (interpolated) photo resolution | 1,2 MP (1280 x 960) |
| Max. (real) photo resolution | VGA (640x480) |
| Max. video resolution | VGA (640x480) |
Download Tech Spec sheet (PDF)
The following links and references may be useful:-