Could any one help me with a recommendation or online site that sells spiders? Preferably in Australia would be better. This is the last piece I need to begin my project which is a 16" truss dob.
Woa!!!, $170 is the price at bintel, didnt realise they are so dear!!!
The telescopes-astronomy website seem ok. Have emailed them for a price.
I think I will most likely make the spider myself, we have 2mm and 3mm stainless steel at work. What are the usual thicknesses for the spider vanes in larger dobs? Is 2mm plate overkill?
Hi Mark. I made my spider out of the strapping that holds bricks and tiles together in pallets. It's made out of steel and is thin abd strong. You can also drill it without breaking. You can find it lying about on most building sites as it is rubbish. It also comes in black, sometimes green. I cut two lengths the same size longer than the with of the tube. I got a piece of square tubing about 3.5cm x 3.5cm (it can be out of any metal) your's can be bigger because of the secondary size. I drilled 5 holes into the square tube 1 small to let the secondary screw fit in and 4 bigger to let the adjustmentscrews fit. On the opposite side of the large holes I made 4 smaller holes to let the end of the adjustment screws in, These I tapped. I attached the strapping to the side of the square tube with rivets. I then got some threaded rod from bunnings and I cut out 4 pieces about 5 cm long (you can use anything with thread in it). I then cut out a slit in the rod to fit the strapping in drilled a hole in the rod and the strapping attached a pin to hold it in place passed the rod through the tube attached wingnuts to the end for adjustment. Here are a few pictures hope it helps. Total cost about $10 to $20. and 1 days work. I used this set up on the truss telescope I made and have seen it used on bigger telescopes as well.
Spider vane thickness needs to be as thin as possible.
For the last few I have used 0.5mm Stainless steel as well as guitar strings (high E which is 0.011"). Stainless is easier. I used 1cm square aluminium tube from my local Al supplier. Fitted bored end caps to allow an 8mm threaded rod to be centred properly. Bent the stainless into a v shape with a flattened base, drilled two holes through the small flat of the vane to secure it with small bolts to the square al tube. Drilled the tip of each vane to take a 1.5mm stainless pin which hold slotted threaded rods. Painted with Krylon matt black. I use an orthogonal collimation system so that the heads of the collimation bolts are accessible past the spider vanes.
Thanks for the advice guys!
Ive decided to go with making the spider myself. $170 is just too much for a few bits of thin sheeting bolted together.
I have access to .9mm Stainless sheeting so that will have to do.
I can use thinner stuff also but have found that it is easily bent and then is very hard to get the bends out of it once bent.
