Sounds like your secondary collimation mechanics are awry. Like Eric said, the primary mirror bolts will have no effect on this, this is 100% adjustment of the secondary mirror.
If one of the bolts is not working, then you have either a stripped bolt, or some other issue.
My GSO and you lightbridge share the same 3rd party vendor of the spider assembly, I think.
Smooth collimation of the the 2nd mirror depends on the right tension
balance between the spring-loaded center bolt and the three collimation
screws. The center bolt at its top isn't fixed to the vane, but rather
wiggles and pivots a bit, thereby allowing the secondary to "wiggle"
when all three collimation bolts are loose. This wiggly center bolt is
holding the secondary to the vane, but the spring around it is pushing the secondary away. This degree of wiggle is determined by the tension of the
spring of the center bolt. The tighter the secondary bolt, the more
tightly compressed is this spring. If the spring is too loose then the
three collimation bolts, as they move down to push against the fender
washer, don't have much to move before they "push" the secondary beyond
the tension of the spring. The result is clunking of the secondary when
you try to adjust the collilmation bolts. You need a longer spring,
or a more tightly compressed spring anyway. The right dynamic tension is this system is necessary for smooth non-erratic and non-clunky collimation. Some springs are floppier than others; I needed to add some washers to my bolt to effectively over-compress the spring to get this correct degree of tension. That may not be your exact issue, however.
If one of the bolts isn't in contact with the top of the secondary mirror holder, that may explain why your one collimation has no effect, as you describe. A broken bolt, or its stripped (or the spider hole threading is stripped) and not really moving down when you turn it.
If you can't get it to work, try taking a picture of where the center bolt of the spider vane assembly screws into the secondary mirror holder itself. This should also show the three collimation bolts making contact with the fender washer on the top of the secondary holder.
Hope this makes sense and helps.
ST
Quote:
Originally Posted by sejanus
argh
So I have the trusty laser pointer in the eyepiece. The red dot appears about 4cm from the dot in the center of the mirror,.
No matter what I do to the screws on the spider, I can't get it in. I can get it to move around to the left, right, down, but not up.
The obvious answer is that I need to adjust the screws on the base of the mirror right? The problem is that adjusting these screws, the red dot doesn't move in the slightest.
What am I missing?
thanks
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