For a discussion about projection attachments go to: Projection Attachments
A lot of fun with video imaging of the moon, sun and planets can be had with an appropriate video camera and lens attachments. With a sensitive camera and a fast photographic lens, brighter stars can be imaged as well.
I have chosen the GBC 505E camera as the imager and have made a number of lens
attachments. The camera with the control box I made and a 2" projection
lens adapter is shown in the figure. The four projection lenses I use
are small, fast and very high quality microfiche projection lenses. These
are ideal for projection magnification of the aerial image created by the telescope.
The four lenses are 10 mm, 17 mm, 22 mm and 32 mm. They are placed 250
mm from the image CCD with the tube shown. These give magnifications of
25X, 11X, 15X and 7.8X respectively. These magnifications are just right
to place planets on the 12 mm chip in the camera. This is a very nice
camera with 800 by 600 pixel resolution and extraordinary sensitivity for a
video camera of 0.01 foot candle and a usable image at 0.001 foot candle.
It runs on 12 volts and puts out an S-VHS signal. I have built a separate
power supply for it with full voltage regulation and a gain control. The
camera can be operated at the end of 100 feet of remote cable easily.
The camera can be used with four different lens arrangements. One is the projection tube shown in the first picture. The 2" tube gives excellent rigidity to the structure which is placed directly into the opening on the JMI focuser. Rigidity is essential because of the large magnifications involved in planetary imaging. The four projection lenses shown fit into the tube at the location shown by the set screw. The lenses are inserted from the camera end and locked into place with the set screw. They are of course used in the retro projection orientation to ensure the best possible projection quality. True projection lenses give superior quality to eyepiece lenses which are not designed for projection use. Some of the photographic references given on this web site describe the use of projection lenses in more detail. The projection tube itself is designed to do triple duty as a projection imager for a Canon camera and for the ST-7 as well as for the Video camera. It is fun to image planets in real time on a video screen while recording them on an S-VHS VTR. There are moments of very clear viewing that can then be captured and still framed.
Another mode for the video camera is to use any canon lens with it. Adapters have been made to use the standard Canon bayonet mount on the ST-7 and the Video camera. All adapters are par focal with the Canon camera. On the right above the video camera is show with an 85 mm f 1.2 Canon lens. It is mounted in a custom made holder that holds it firmly balanced and allows it to be placed on a piggy back mount on the telescope. I use the Losmandy camera adapter. With a fast lens, a bright star field can be seen and the video camera used as a finder scope. With longer telephoto lenses, the lenses themselves typically have mounding frames built into the lens.
Finally, the Video camera can be used with standard C mount lenses. The
last two pictures show the camera with a standard Canon lens, focal length 135
mm f 2.5 and with a C mount lens of focal length 75 mm f 1.4. Faster,
slower, longer and shorter lenses are all quickly interchangeable and par focal
using the adapters shown.
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