Newtonian Secondary hub for wire spider (88mm + flat)

Enjoy sharp, crisp views without spikes on stars!

Not much to say.  Use silicone adhesive, 26 gauge steel wire and haywire twists (or guitar string) with 8 guitar tuners spaced in a square normal to your focuser.  The secondary I used is 88mm; in general, the secondary needs to be big enough to conceal the hub behind it.

This has a 4mm offset built into it, but note that collimation adjustments on the back will change that.  If you center the mirror in the holder, and center the indicator (indented diamond on top of holder) you will have a 4mm offset built in.  Further offset should be managed with the wire spider and a ruler.

I do not have a jig for this yet. I will be making one soon.

Hardware needed:

• m5 heat-inserts x 3 (or x7; I prefer to put four in the outside corners of the holder to keep the wire from cutting into the plastic)
• 3x comfortably long m5 bolts (40 or 50 is perfect) preferably thumb or socket head
• 26 gauge steel wire or 8 thin guitar strings
• 8x guitar tuner
• 3 small sturdy springs that fit over m5, if you want extra collimation ability

Make sure to print it sturdy.  I used 4-6 walls (0.6mm nozzle) and 30 or 50% cubic infill.  (Do note that increasing walls is better for sturdiness than increasing infill, and beyond 50% infill returns are not significant).  After all, this has to hold a big piece of glass perfectly still.

Do keep in mind: your glue will affect your offset to the tune of a few mm.



  If this jargon means nothing to you, do one of:

• read up; this is only mildly complicated, but the knowledge is scattered across the old and new internet.
• find me on discord 
• find a place where I have put more documentation.
• re-think making such a complicated telescope.

I'm hosting the files for my 16-incher for anyone to follow in my footsteps, but these are just provided as-is.