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VSI's Accu-Port Targetron

Finally, an Off-Axis Guider with the Functions & Features you Need!

Targetron Off-Axis Guider

2-Axis Guide Star Acquisition, 2.75" Aperture, 1.5" Profile

VSI's Accu-port Targetron off-axis guider offers a contoured European styling and super smooth, sensitive dual-axis control. Although The Targetron may resemble other off-axis guiders on the market, its superior function, operation, and performance is in a league by itself - like no other on planet Earth. VSI knows of no other guider that has scan (Y-axis) and seek (Z-axis) capabilities, except our Slider and Sidewinder optical manifolds, which also have full-field slide-mirrors that are instantly removable from your camera's straight-through field of view.

The Targetron's extreme build-quality and thick-wall construction are typical of all VSI products. Optional docking and camera port rings are interchangeable, providing installation on any scope or any camera. Coupling to the Targetron body is rock-solid via three set screws opposed by 120 degrees that lock into a flared flange (circular dovetail). This mounting not only clamps the ring in position but laterally compresses the ring inward to form a weld-like connection. A visual indented dot indicates rotational position at a glance, so you can instantly see your port position around the 180 degree arc.

The Targetron's large-format design offers a full 2.75" clear aperture, with a super-short 1.5" profile. The inner, non-rotating cylinder is one-piece construction, from front to back, so your camera remains stationary during rotation of the pick-off mirror. Most important, the optional docking and camera port rings mount to either side of this solid, single-piece inner ring. This exclusive mechanical design creates a zero-flexure coupling between your scope and imaging camera. The outer, rotating cylinder swings (Z-axis) your pick-off mirror a full 180 degrees (see below for illustrations). This is more than enough rotation to find an adequate guide star, even in star depleted fields. And, the rotating cylinder has double Nylon thumb screw locks. The other Y-axis rotates the 1.25" format port on two ball-bearings, offering a complete scan of your scope's field of view at every rotational Z-axis stop, multiplying your chances of finding a usable guide star (see below for illustrations). A convenient lever rotates the Y-axis scanning port with ultra-sensitive, leveraged tactile contact. The amount of effort exerted on this lever is adjustable using the dual thumb screws pictured below the rod itself (see left picture). These thumb screws also lock the port in place when a guide star is found. The Targetron's pick-off mirror tube adjusts in and out of your scope's light cone, providing exact positioning for any focal length scope and any CCD chip area or 35mm camera format.

IMPORTANT NOTE: The Targetron is a specific application off-axis guider not designed for general off-axis use. If you must have an extremely short profile guider (1.5") with a very large internal clear aperture (up to 2.75" depending on port rings used) then the Targetron is for you. However, if you are looking for a general application off-axis guider, then our 2" format Sliders or larger-than 2" format Sidewinder optical manifolds will serve you much better.

Features & Specifications: Accu-Port Targetron Off-Axis Guider

Accu-Port Targetron Off-Axis Guider

VSI's NEW Accu-Port Targetron off-axis guider features Y-Z axis pick-off mirror control and rock-solid construction throughout. Internal clear aperture is a full 2.75" with an ultra-short 1.5" housing profile. This is the shortest profile possible, given the mechanical and physical parameters of the product. Depending on your port ring requirements, overall profile may increase by only 0.1 to 0.2 inches.

You can also attach a MicroGlide Epsilon focuser, with Robo-focus computer control, to the output of the Targetron guider using our  0.1" low-profile Docking Ring, 2.7" to 2.9" for mounting (see picture at right). Adding our MicroGlide focuser (discontinued but still available, see Discontinued Focusers link) to your imaging train will increase your profile by 2 inches, but provide easy autofocus control without modifying your existing scope's focuser, which can cause [out-of-focus] too coarse stepper motor ratios. If you aren't exactly sure about installing universal aftermarket stepper motors on your existing focuser, then a MicroGlide autofocuser is the best way to go, to insure step ratios way below what you need for pin-sharp images. MicroGlide autofocusers provide the finest autofocus motor ratio available, by a factor of 10 better than any other autofocuser on the market - one motor step = 0.0000069" of actual tube travel!. After installation of the auto-focuser, you can easily parfocus your pick-off port with your camera by using our 1.25-inch to 1.25-inch Drawtube: Item #AD11 Price: $39, or you can use your existing 1.25" diagonals to consume profile (see "CCD & 35mm Camera Applications" below).

We can machine custom Targetron [or Zerotator] ports for your scope's field flattener (see Targetron pictured at left). All field flatteners need a specific amount of space between the field flattener lens and the CCD chip. This distance is usually enough (a few inches) to install our Targetron off-axis guider between your field flattener and your CCD camera. VSI created custom machined Targetron ports so that a client's field flattener spacer tube (69mm length) could be replaced with our Targetron off-axis guider. Now he has a wide-aperture, off-axis guider between his Takahashi TOA 150 refractor's field flattener and his SBIG STL11000 CCD camera without sacrificing any of that valuable profile. Our client really had a great idea that utilized his existing profile! Note the left Targetron picture with the Tak 92mm threaded docking port on the left side (Tak field flattener) and the extended SBIG 2.156" threaded camera port on the right side (SBIG CCD camera). 

The pick-off mirror tube is adjustable [in and out] by loosening two set screws and push-pulling the tube to the desired position. A total of six Nylon thumb screws lock the [two ball-bearing equipped] Y and Z-axis [friction] rotation, and your eyepiece or CCD guiding camera's barrel-nose in place. The shiny indented dot just above the pick-off mirror between the two [center] black Nylon thumb screws (top right picture) indicates Z-axis rotation position around the 180 degree arc. Base unit only. Purchase optional docking and camera port rings below. Eyepieces and cameras not included. 1.25" format top pick-off port. Targetron weight (less port rings) = 13.5 ozs.

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Y-Z Axis Control plus IN/OUT Mirror Adjustment

Our NewTargetron off-axis guider is like no other, featuring 2-axis control and IN/OUT pick-off mirror placement. It doesn't get any better, anywhere. No other off-axis guider, except our own Sliders and Sidewinders, offer this kind of multi-axis operation. You are guaranteed a guide star, on the first search, or "it's [NOT] full of stars," which means it's cloudy, and there is nothing we can do about that. 

The Z-axis rotates a full 180 degrees with the slightest touch of the port, yet the double Nylon thumb screws lock the axis in any rotational position (see picture above right). This separate 3/8" thick outer cylinder rotates separately around a one-piece inner cylinder. The one-piece inner cylinder provides rock-solid scope to camera coupling, without camera rotation, when you rotate the Z-axis. In other words, the camera remains fixed like a solid coupling [which it actually is], while you rotate the pick-off mirror around it's field-of-view. This is important, because a rotating pick-off mirror and camera means there has to be a bearing (radial, thrust or otherwise) in the mechanism and that can only induce flexure into your imaging train. The only lateral rotation that is zero-flexure, I know of, is our custom-machined Crayford Disc Rotators. They are zero-flexure because they are Crayford in design. As we all know, Crayford means zero-flexure, whether it's moving a tube in and out, or rotating around in circles (see MACHINING link at the top of this page for more pictures and info about our Crayford Disk Rotator).

The Y-axis scans your scope's field-of-view, for a suitable guide star, at each stop point around the rotational Z-axis. The Targetron's 1.25" pick-off port rotates in its socket, which is held in place by two ball-bearings. Adjustable tension is applied to these ball-bearings by the two Nylon thumb screws located at the base of the port. These tensioning thumb screws can be adjusted to apply minimal pressure for rotation of the port. With minimal tension, you simply rotate the lever (pictured above left) across your scope's entire field-of-view, scanning for an adequate guide star. When you find one, just lock the port rotation down using one or both Nylon thumb screws.

Initially, you need to set the distance you want the pick-off mirror tube to protrude into your scope's primary light cone. This position will depend on your scope's available clear aperture and the size of your imaging CCD chip or film plane, usually 35mm format. With a small clear aperture scope, you will need to place the pick-off tube so that its mirror just catches the edge of the scope's light cone, no more. With a large clear aperture, like a refractor with a 3 or 4" focuser, you usually set the pick-off mirror as far out as it will go, at the edge of the Targetron's 2.75" clear aperture. With a large chip camera, you will obviously need a scope with a large aperture, which also means you would place the pick-off tube at the edge of the Targetron's aperture. With a smaller chip, usually any place in between the edge of the smaller chip and the edge of your scope's available clear aperture will suffice. Two set screws, opposed by 90 degrees, hold the pick-off mirror tube securely in place.

CCD or 35mm Camera Applications

Our phrase, "Any scope, any camera" can be taken quite literally. Whether you are doing CCD or 35mm imaging, the modifications to your Targetron and imaging train are minimal, if at all. With a CCD camera, the Targetron's pick-off port should be relatively parfocus with your CCD camera, as is. No adjustment, except for the pick-off mirror tube IN/OUT placement, should be necessary. Simply push/pull your guiding eyepiece or guiding CCD camera to parfocus with your imaging camera. From over a decade of imaging experience at Black Forest Observatory, we've found that push/pull port focusing is much quicker and more efficient than any redundant helical focusing system.

With a 35mm camera, you will have to extend your illuminated reticle eyepiece or guiding CCD camera out about 1.5" to parfocus your system. You can use our 1.25-inch to 1.25-inch Drawtube: Item AD11 Price: $39, or you can use your existing 1.25" diagonals to consume profile (see picture below). You can use an illuminated guiding eyepiece (pictured at right and below), like the ones offered by Celestron, Meade and others, or you can use a separate CCD autoguiding camera like the one offered by Starlight Express SXV-H9C (pictured at left) with the separate guiding camera that slips right into the Targetron's [1.25" format] off-axis guiding port - a marriage literally made for heavenly imaging! As we also say, "the possibilities are limited only by your imagination."

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