A while back, we bought a new Astro-Tech AT-10D scope to replace our previous EQ-mounted Newt. It arrived just in time for a lot of things to suddenly change in our lives so we put it in the back of the closet without looking through it even once. A few years went by and the eclipse caused us to haul it back out and things are not good. Specifically, the view through it is much, much worse than our old 8" Newt. Yes, the new scope is properly collimated from first principles using all the Catseye toys. I am getting close to having examined and ruled out all the stuff I know of that can be wrong with a Newt but tonight I noticed something odd that maybe will give you guys a clue to help me find the solution.
The scope has a traditional 4-vane spider where the vanes travel straight across the tube through the center. This is supposed to result in 4 strong diffraction spikes every 90*. I'm getting eight spikes. They do occur every 90*, but instead of one bright spike, I have two slightly dimmer ones offset from each other a small amount. It's almost like looking through a rear-surface mirror where you get a reflection off the front of the glass and a reflection off the silver behind the glass and they're just slightly offset because of the thickness of the glass itself. The spikes are parallel but not coincident.
Any idea what this means?
Edited by Ty Williams, 25 August 2017 - 11:05 PM.