VSE\'s Home Page Versa-Port Sliders Mega-Port Sidewinder Accu-Port Targetron Imaging Train Rotator MacroGlide Focusers MasterGlide Focusers MicroGlide Focusers Hexagonal Turrets BiFilar Micrometer Spiders

Order Info FAQ astroimaging User Installations User Comments Astro Links configurations help Custom Machining
SAVE 50% - WHOLESALE PRICING DIRECT from the MANUFACTURE
Why pay RETAIL for the mediocre, when you can have the best for less!

NOTE: Robo-Focus stepper motor equipped spiders require electronics hardware package ($295) purchased separately from [Go to] Technical Innovations [web site]. Also requires CCD camera, computer and appropriate software (i.e. CCDSoft, MaximDL, FocusAide, etc.).

NEW Manual & Motorized Secondary SPIDERS for Newts & Cassegrains

Revolutionary Floating Ball & Socket Adjustable Head Design

Features & Specifications: Secondary Spider Assemblies

Manual (push-pull-rotate) Spiders for Newts & Cassegrains

VSI's new spider assemblies offer a revolutionary head adjustment design. Until now, all you had to select from were wobbly 3-spring heads or dysfunctional 4-screw push-pull heads. The former never maintained alignment and the latter was extremely difficult to adjust - tighten/loosen, tighten/loosen, etc., etc. With VSI's new ball and socket design, all you have to do is turn any of the three Allen head bolts clockwise or counter-clockwise, using the included 9" long Allen T-handle wrench (pictured above). No loosen/tighten forever scenario, and the head stays rock-solid and perfectly centered because the "floating" ball is always in the center socket.

The manually operated spider hub has a solid stainless steel (SS) shaft that is loaded to maintain a zero-tolerance in any position and has double [quarter-turn] metal thumb locks (non-motorized only). It is simple and functional offering push-pull-rotate head positioning for Newt diagonals and push-pull operation for Cassegrain secondary optics. There is also an optional 2-Axis Shaft Micro-Collimator (see picture/info below) that will offer perfect Newtonian secondary mirror alignment every time. With Newts, once you have your diagonal in the mechanical [shaft] position you want, simply adjust the three SS Allen head bolts to fine tune your alignment. With Cassegrains, simply align the head using the three SS Allen head bolts and push-pull to set your back focus. Cassegrain SS hub shafts offer 3 inches of travel for the SH3, equating to 18" of adjustable back focus, and 5 inches of travel for the SH4, equating to 30" of adjustable back focus. No more flexure-ridden drawtubes when changing visual back configurations. Just loosen the double thumb screws and push-pull to set your desired back focus. Your head alignment is always perfect, no matter where you position it, because the hub/shaft always maintains a zero-tolerance.

VSI's NEW [optional] 2-Axis Shaft Micro-Collimator (pictured at right) provides two additional axis of micro-adjustment above and beyond the omni-directional head adjustment pictured above left. To our knowledge, this unique collimation device is exclusive to VSI and has never been offered on any Newt spider assembly in the past. The Micro-Collimator adjusts the spider rotationally and up and down by the simple turn of thumb screws. The large aluminum knob on the right push-pulls the shaft and the two black thumb screws on the left rotate the shaft clockwise and counterclock-wise. This simple and effective device offers critical Newtonian secondary mirror alignment that has never been possible before now.  

At left is a picture of the vane hub, SS shaft and head assembly. Note the SS ball centered between the two disks. Each side of the "floating" ball (spherical to 25/millionths of an inch) is suspended in sockets allowing the lower disk to be rotated, using the three Allen bolts, while maintaining perfect center alignment. Of special note, look at the two-piece washers under the Allen bolts above. Those are spherical dish & seat washer sets, imported from Germany. They are machine trued and case hardened, always providing perfect bolt alignment, even when the lower disk is misaligned with the upper disk. Also note the SS nuts at the end of the Allen bolts. Those three nuts can be tightened when alignment is achieved. Notice that I said, "can be." Locking the head is really not necessary, unless you are taking your scope to a star party, etc. Even then, extreme vibration could not dislodge your alignment without these nuts locked in place. These three nuts are simply there because they can be, not because they need to be. And if you do happen to use them to lock the head, they work with the pull of the bolts, not against them, so tightening them changes nothing, alignment wise.

At right is a close-up picture of the the end of each vane, where it attaches to your telescope's tube assembly. Instead of using single-point swivel bolts, like other spider vanes, VSI uses a full-length slotted plate, which is bolted at both ends of the vane to prevent this swivel motion. This rigid method of vane-to-tube mounting provides a more solid spider installation compared to single, swivel-type, split-bolt designs.

Motorized Spider Hubcans for Remote Focus

Pictured at left are three motorized [what I call] hubcan assemblies, shown without vanes or Cassegrain/Newtonian head. These "hubcans" are not real cans, like soup, etc. They simply looked like cans, thus the name "hubcans" like hubcaps, etc. These hubcans are 1/4"-wall aircraft-grade 6061-T6 extruded aluminum with machined ribs and 1/4" plate aluminum [top and bottom] caps. All VSI pshaftucts are exclusively constructed from two metals [including hardware], the above grade of aluminum and stainless steel. All motorized hubcan configurations provide 3" to 5" of travel (18" to 30" back focus range), discussed in more depth below. These hubcans are available in four different motorized configurations. Three are pictured at left, (1, SH3 left & 32" SH4 spider shown below) Robo-Focus stepper motor (needs Technical Innovations electronics hardware package) with temperature compensation providing a shaft movement to step ratio of 0.000021" per step, (2, SH3 center) DC servo motor control with analog dial indicator and hand paddle (shown at right), (3, SH3 right) DC servo motor control with digital read-out and hand paddle (remote location DRO display box pictured below right). (4, not shown) is the DC servo motor control hubcan with hand paddle, no analog or digital read-out. Optional analog dial indicators and digital read-outs are not available for Robo-Focus stepper motor equipped hubcans. This is simply because the stepper motor body is too large to accommodate the indicator or read-out, and you don't really need this redundant local feature since you have focus position, etc. via your computer's software.

Because of VSI's exclusive off-axis helical screw [non-rotational] design, there is literally zero star wobble when focusing. Many other designs use a complicated on-axis helical design to move their spider heads in and out. Our simple zero-tolerance design guarantees zero "everything" when focusing. No wobble, no flexure, no backlash, no lateral anything. Just perfect linear in-out movement. Our motorized hubcans offer a full 3" to 5" of travel, depending on model. Since primary/secondary separation usually equates to a 6 to 1 focus ratio (depending on your focal length), you receive 18" to 30" of back focus range behind your visual back with the push of a button!

Motorized hubcans [electrically] connect their motors and digital read-outs to the outside world via an optionally installed multi-conductor flat cable strip attached to the side of one spider vane (shown at right & below). These special ultra-thin cable strips are only 0.004" thick. Yah, that's four/thousandths of an inch! Since the stainless steel vanes are 0.024" thick (0.060" thick for SH4s), the cable strip is microscopically thinner than the vanes themselves. That factor renders the cable strip thickness negligible to the "spider spike gods."

A motorized secondary spider is not just a luxury for your Cassegrain. Even if you already have a primary focuser behind your visual back, you need a motorized spider for many reasons. Mainly, to change your existing back focus for your various equipment configurations. Why use awkward, flexure-ridden drawtubes, when you can simply push a button to change your back focus to exactly where you want it. Then simply use your [now] secondary focuser to fine tune things. This mode of operation was my favorite during the days of Black Forest Observatory and the 30-inch Cassegrain (see Installations link, bottom of the page for more info). To change from visual to imaging mode, I had to move my back focus point outward by about a foot or more. Since the 30-inch was equipped with a motorized secondary and a standard visual back focuser, all I had to do was push a button to move the secondary closer to the primary and increase my back focus point. What a luxury! And very functional, too. Or, you can use your motorized spider to completely eliminate the profile consumed by your "behind the visual back" conventional focuser. I shouldn't say that, since VSI offers the largest selection of primary and secondary focusers on Planet Earth. Seriously, a motorized spider can make your focusing efforts much easier and less frustrating.

Many zealots think that the distance between primary and secondary Cassegrain optics should be fixed at a point that is mathematically and optically correct. This is perfectionist rhetoric. Sure, there is an ideal [Cassegrain] separation between the primary and secondary, but this can vary by many inches, and you or your camera will not know or see the difference. Commercial Schmidts and Maksutovs change this separation by moving their primary back and forth in relation to their secondary optics. It works great. To continue briefly from the above paragraph, I created a motorized secondary for my 30-inch Dall-Kirkham Cassegrain that had a 6" range of travel, allowing me a whopping 36" of adjustable back focus range. Again, it worked great. My 10" Ritchey-Chretien changed it's back focus by turning a knob on the sky side of the secondary hub (more about these scopes at the Installations link, bottom of the Installations page). I noticed no aberrations, spherical or otherwise, when the separation was extended all the way in or out.

NOTE: Robo-Focus stepper motor equipped spiders require electronics hardware package ($295) to control Robo-Focus stepper motor purchased separately from [Go to] Technical Innovations [web site]. You also need a CCD camera, computer and appropriate software (i.e. CCDSoft, MaximDL, FocusAide, etc.).

[return to home]

[top of the page]