MY TOUCAM PROJECT
Foreword..
What has happened!! Philips have produced a good low level web cam that is ideal for astrophotography and broken the code by using a high quality CCD array instead of camera chip floor sweepings that appear in other manufactures web cams...
Quick moon pictures are easy..you only have to be careful about the exposure and contrast as the image is so bright.
I have experimented with web cams or web cam variations for some time ,however none of these match the Toucam for planetary image performance.The reason for this can be resolved from Nyquists Theorem and the following equation Resolution in arc seconds equals (CCD pixel size in microns/focal length in millimetres) multiplied by 206. As the toucam pixel size is 5.6 microns if you put this into the equation then you get a result of the camera coping with a telescope resoluton of 0.35 arc seconds for a focal length of 3metres which is what you need to image planets.Most amateur telescopes only just go down to this if you are lucky so the camera always out performs the telescope.I have made the SC1 mod with my own version of the method of achieving it. In my case I used a cmos switch in two forms.It is possible using the integrated circuit types DG418 and DG419 to create a single pole switch and a single pole changeover swich under control of the parallel port of the pc.If you have to connect out another line to control time exposures other than the USB connector then it is also as easy to take out two lines. I removed the Toucam printed circuit board from the camera original body and fitted that into a diecast box.A turned fitting to make it fit into a one and a quarter inch eyepiece holder was the only other requirement. The camera dust seal was achieved using a filter screwed into the end of the adaptor.For this I used a standard 'skylight 1a filter' from celestron.It was only necessary to cut a circular hole in the top of the diecast box for the light to get in and also a small slot in the side to hold the USB cable gland. Control from the parallel port was via a stereo 3.5 mm socket in the side of the diecast box.The changeover cmos switch puts the camera in and out of time exposure mode and the single cmos switch controls the shutter.Most of the time spent however has been involved in writing software to display and capture the images.This has been written in visual basic around a commercial video capture ocx.This also allows me full control of the Toucams functions,still frame capture,avi recording,multiple frame avi recording and software analysis of images from my Hartman Mask for focussing.
The Circuit for my SC1 modifications is hereNotice that the Toucam runs from a 3.3 volt regulator so that any pull up resistors going to the internal chips should go to 3.3v not 5 volts USB.The DG switches have to work at 5 volts to cope with the input from the computer parallel port that runs at 5 volts.The circuit board was glued onto the chips on the back of the toucam circuit board to mount it as shown in this picture. The standard method of conversion with this camera is to solder on the wires to the external circuit, test the camera then cut the tracks.The only different thing that I did from most people was not to solder onto the toucam chip pins.I traced points where there were feed throughs in the board ,removed the paint from them and soldered onto those points.Even though I have a temperature controlled soldering iron with a 1 mm bit I found it almost impossible to solder on the chip pins reliably due to not being able to hold the iron steady enough and so shorting out pins with difficult to remove solder.You also have to remember that to get the absolute maximum out of a Toucam image the image itself has to cover an area on the chip up to 320 pixels wide.This is more true with saturn than any other planet due to the rings.If you take an image from the Toucam that is smaller and blow it up on screen you will se that there are simply not enough pixels in the image to improve detail such as the cassini division.What you are up against with the telescope then is the need for focal length to produce this large image which turns out to be seven metres.The next problem is light as the image by this time has dimmed down and the Toucam runs out of steam into the noise.Consequently the best images come from newtonians with 14 inches of aperture with 5X barlows attached that are operated in perfect atmospheric conditions relative to temperature and moisture in the air stability locally and also in the telescope atmospheric column out into space..
Mars is now coming into view and hopefully the images of it should get better.
Partially lit from and not at opposition yet ,this image would not have been possible without Registax as the image was wriggling like a snake.
Slightly better and getting closer. Images taken using the takahashi FS102 with 3X barlow resolution 1 arc sec
Image taken using the 12 inch LX200 classic resolution 0.4 arc second with a 2x meade barlow.
It is amazing what difference being a few miles closer can make.A point of note here is that this image has been done behind an iris diaghram placed approx 30mm in front of the camera chip.This allows precise adjustment of exposure in combination with the normal electronic camera controls.I have always found this useful even years ago doing visual study of planets.This was used with filters sometimes but mostly without.If you do not have such a device it is also practical to make a shaped plug like a bottle top out of Baco foil with a hole in the center and slide that into the camera port.The hole needs to be approximately 3mm but depends on the aperture and light gathering power of the telescope.Basically.. experiment with holes.
The image was also taken at 3 AM in the morning with vastly superior thermal conditions locally.
December 2005 this is using a VC200L telescope with a 2x Meade barlow..
Both of these were late december and well past opposition now as you can see from the planetary illumination.
Images taken using the Vixen VC200L resolution 0.6 arc second.
It would be wonderful if the telescopes above could work at the resolutions stated but in actual practice they would have to be in orbit for that to happen.Maybe in a few years time you could contact a company called Earth orbital tours if you could find the odd few hundred thousand pounds for the fee and do HST impressions with your own telescopes.One can but dream.
