My secondary is bending after re-installing it! How do I make it stop : (

[pipnina]

I took my seconary mirror out of my TS-PHOTON 8" f4 today to blacken the side edges, since it would be very hard to do a neat job with it in situ (already tried).

With the job done, I went to put it back in and found that as I tilted my telescope from pointing straight up to facing... we'll say north. The laser dot moved away from the center of the printed donut on my primary. Weirdly, it did not move from the upright position when I tilted it "south".

I tried re-adjusting the collimation screws, making sure my distances were correct (90-92mm length for all 4 spiders). I even figured maybe there wasn't enough tension and used a mini pipe wrench to tighten the spider vanes more. Sadly, to no avail.

I can't think of any other reasons it might be flexing so, It wasn't before... Secondary collimation remained rock solid, and primary remained quite good once I used the silicone sealant trick. I nudged the laser in the focuser and it didn't move as much as when tilting the scope, and even finger nudging is more than gravity will be applying to the focuser.

I noticed that if I put my finger on one side of a spider vane, and my thumb on the other side of the opposite spider vane, the secondary would move in the same axis as the telescope tilting error. And this happened whether I chose the up-down pair of vanes or the left-right pair!

Wishing I persevered more with applying the blackening in situ now...

[Ricochet]

My guess would be that you need to tighten one of the secondary collimation screws. When you tilt the telescope in the direction that makes the laser move, it is probably the collimation screw that is on the bottom that needs tightening. 

[pipnina]

5 hours ago, Ricochet said:

My guess would be that you need to tighten one of the secondary collimation screws. When you tilt the telescope in the direction that makes the laser move, it is probably the collimation screw that is on the bottom that needs tightening. 

I've given that a go. Loosened all 3 off and then re-collimated, not tightening any one too much in one go, making a few passes around so they all get done up evenly. Dot still shifts a bit on the primary although maybe not as much. I did try tightening them a LITTLE extra with my pipe wrench on the screwdriver (only a small phillips head) but that didn't improve it.

Not sure what I've done wrong here...

[ONIKKINEN]

22 hours ago, pipnina said:

I noticed that if I put my finger on one side of a spider vane, and my thumb on the other side of the opposite spider vane, the secondary would move in the same axis as the telescope tilting error. And this happened whether I chose the up-down pair of vanes or the left-right pair!

 

Is the tube deforming under the tension of the spider supports?
Something is not tightly held, or otherwise there would be no movement.

[pipnina]

1 minute ago, ONIKKINEN said:

Is the tube deforming under the tension of the spider supports?
Something is not tightly held, or otherwise there would be no movement.

I did pinch the tube on one support, one of the supports bent a little at the tube wall end after I eventually did them all up far enough.

Hopefully those aren't the issue but I was surprised I had issues to begin with, since one of the spider screws wasn't fully finger tight when I bought it and it was secure then.