The Taurus astrophotography system was designed solely for use with a telescope and therefore has several advantages over conventional SLR cameras. The system was reviewed in Sky &Telescope (January, 1995). The following is my impression of the Taurus system.
The tracker (T1) is the equivalent of an off-axis guider. The pick-off mirror is larger than that of most off-axis guiders and seems to produce brighter guide stars. Other users have reported difficulty in locating guide stars with the Taurus tracker. However, I believe this is due to the 2.5x Barlow incorporated in the elbow assembly which makes it difficult to use a 9 mm guiding reticle. A 12 mm reticle may give better performance with this system. The elbow joint on the guiding port of the tracker is an interesting concept and allows the user to rotate the guiding reticle to a more convenient viewing angle. For autoguiding, the elbow/Barlow is removed and the autoguider is placed directly into the guider port. I have not had any difficulty in locating guide stars and find the system superior to Celestron's radial guider.
The tracker easily rotates about the optical axis facilitating the selection of a guide star. A knob on the tracker also provides radial movement of the pick-off mirror, but this adjustment is too sensitive making it tricky to center a guide star on an autoguider.
Besides serving as an off-axis guider, the tracker contains a viewing port. The viewing port is a unique and powerful feature that allows you to locate and center an object without changing the configuration. A flip mirror selects the camera or viewing port. A new user is apt to ruin several photos by forgetting to return the flip mirror to the camera position. Nonetheless, the viewing port is one of the nicest features of the Taurus system.
The camera (C2) is very simple. It consists of a film advance knob, a rewind knob, and a sliding shutter that can be locked open or close. There is no mechanical shutter or timer, and thus exposures less than a few seconds are not possible. The camera attaches to the tracker by tightening 4 thumb screws. Magnets help guide the camera into position on the tracker.
The focusing method is perhaps the nicest feature of the Taurus system. A 12 mm eyepiece is inserted in a holder and placed on the calibrator. A lit ring in the calibrator is brought into focus by adjusting the helical focuser on the holder and locked with a set screw. This procedure need never be repeated. To focus the telescope onto the film plane, the eyepiece and holder are attached to the tracker using thumb screws. Magnets help guide the holder into position. The telescope is then focused as usual while viewing through the eyepiece. The eyepiece holder is removed from the tracker and replaced with the camera. Exposures are now in perfect focus. The focuser and camera are easily interchanged.
An extension tube can be placed between the tracker and camera for eyepiece projection. The extension uses the same method of attachment as the camera and focuser. The result is perfectly focused planetary images. Since the camera lacks a mechanical shutter, the hat trick method must be used. With 200 to 400 ASA film, good planetary photos can be obtained with exposures of 1 to 8 seconds.
The Taurus tracker/camera system barely fits between the forks of my 8" LX200 SCT, making photography near the pole possible but cumbersome. However, the clearance is only about 2mm! I don't know how it will work with other SCTs. With the Celestron focal reducer attached, DEC is limited to below about 65 degrees.
I used a conventional SLR camera with off-axis guider before acquiring the Taurus astrophotography system. The Taurus system is much lighter and easier to use. The viewing port simplifies centering and composing, and the focusing method is precise. I sold the radial guider.
There have been some changes in the Taurus system since I purchased it. There is now an adapter available for the Taurus tracker that allows you to attach a conventional SLR camera. However, I like the Taurus camera and do not intend to purchase this adapter. Also, the new tracker is supposed to have less shadowing of the off-axis mirror, but I have no personal experience with it. The manufacturers can be contacted at Taurus Technologies, P.O. Box 14, Woodstown, NJ 08098.
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