Offset Spider Vane Assemblies

that also incorporate the Diagonals offset ....

This photo shows the offset spider configuration  and were the Diagonal offset takes place.


This is what an offset spider looks like, at first glance it will seem quite odd looking and that it might produce 8 diffraction spikes but this is not the case, it still forms the traditional 4 spikes even though the vanes do not meet at center. The main benefit to an offset spider is its resistance to rotational movement over time, in other words how many times have you tightened your diagonal center bolt and found later that somehow it moved in rotational adjustment and you are right back where you started from twisting back and forth on the center bolt with a wrench. You see most commercial spiders use a diagonal holder that requires you to tighten two nuts with an open end wrench, this has to be the biggest mistake ever made by manufacturers its just creates a frustrating exercise in alignment. As you can see from the pictures I have not fallen into this trap, with mine you just pop in the holder rotate it, tighten two set screws and push the safety clip on. To do the fine adjustments I used 4 bolts not 3, I can't say anymore here, once you try it you will realize the advantage. Another property of the spider is the lack of tension required to support it in a tube, people who use sonotube will experience no depression where the support bolts go through, because it becomes ridged with only finger tight tension. 

SPEC'S & SOME COMPARISONS 

DIAGONAL HOLDER

MIRROR PLACEMENT= is accomplished by 3 equal siliconed points. Some advantages to silicon over shell supports are, quicker equilibrium to outside temp.( no trapped air as in shell ), full use of aluminized surface ( giving less obstruction ), no chance of falling off or going out of alignment ( due to loose screws ), no pressure against mirror ( as a head shell is not the way we support other optics, pushing on the back and pulling on the front? ) easier to clean ( no disassembly ), you can use different diagonal sizes on the same holder ( no need to purchase another holder ).

CENTER SHAFT = (1/4" shaft  for  1.5" , 2.1" diagonals)(5/16" shaft  for  2.6" , 3.1"diagonals)   and (3/8"  shaft  for 3.5"diagonals) all shafts are Stainless steel and have a safety clip.

ADJUSTMENT = 4 point using stainless steel button head bolts.( 3 adjustment bolts and 4 vanes never worked very well one always ends up in front of a vane, never mind the confusion when adjusting it).

 

SPIDER

VANE WIDTH = 3/4" wide by .024" thick steel, for 8" to 12" mirrors.       1 1/4" wide by .030" thick steel, for 13" to 20' mirrors.

VANE CLEARANCE = 1/8" before tube wall.

CENTRAL CROSS PIECES = rectangular aluminum extrusion cross pieces, using the least amount of mass to accomplish the task ( no heavy, heat dissipating central hub ). They are ultra light and ultra rigid.

DIAGONAL OFFSET = is incorporated right into the aluminum cross pieces ( something that was never possible in commercial spiders ).

Installation Instructions


Purchasing can only be accomplished through PayPal
email me with your address so I can add the shipping costs and give you a total

also include your
your specs. tube id., your diagonal size, mirror dia. and your F ratio

Note: All Spiders are #4 vane configuration and come with Diagonal Holder

 gargwolanski@shaw.ca


Spiders for 8" to 10" mirrors = $82.00 Can.





Spiders for 12" to 14" mirrors = $99.00 Can.





Spiders for 15" to 20" mirrors = $120.00 Can.






 gargwolanski@shaw.ca

If you would like to see some examples of my ATM work from the past 20 years go to my

Main Page - The Gary Wolanski Projects

Back to Gary's Astro Fab.