TheSkySearchers

I always wondered if the collimation would be maintained when the scope changes position. Tonight I tried it and found that this is not the case. With the 12" GSO Newt in the home position I rotated +-90 degrees around RA. The laser spot that was right in the center of the donut moved slightly above the donut.

Looking at my secondary it is clearly offset towards the side away from the focuser, byt about 1/4" or so. This offset is apparently enough for the spider vanes to flex a bit - though they look quite sturdy and tight. Maybe the effect is not as bad when the OTA is pointing up instead of pointing at the NCP.

Not sure what to do about this. Of course I casn recollimate each time I change the target but then I have to take the optical train out, refocus, etcetera. For now I'll ignore it and see what I get. Any suggestions are welcome.

Okay, so you say the laser spot moved. What did the out-of-focus star tell you about the location of the secondary?

JayTee wrote: ↑Sun Sep 26, 2021 9:00 am Okay, so you say the laser spot moved. What did the out-of-focus star tell you about the location of the secondary?

I did this while it was still light but I've never been big on star tests, the laser lets me test the secondary and primary separately so it gives me more information. Zooming in on the subs most of ghem look good but there were a few with fans. That appears to depend on what filter is used though.

I should take a ladder next time and see what it looks like when the OTA points up.

It could be the spider. It could be the secondary holder sagging.
It could be the focuser flexing the tube differently (many people have had this issue until the tube was reinforced).
It could be a maladjusted focuser and adjusting the sideway in the drawtube could solve it.
It could be the laser moving in an oversized hole in the focuser--fixable by having a 2-screw attachment in the focuser.