rpnconsult

Very informative, thanks. From the picture I posted above, it looks like the secondary is offset towards the focuser rather than away from it? Is that an assembly error?

I got all of that except: "The secondary shouldn't be attached centrally on its holder, it should be around 4 or 5mm (rough guess) closer to the primary, this is the offset. " Not sure I understand that...shouldn't that distance be controlled by the position of the central bold (i.e. movement towards the primary? Or do you mean that the secondary HOLDER is centered perfectly in the tube but the secondary mirror is glued with a small offset towards the focuser?

Ian - the VX8 came fully assembled. I've attached a couple of pictures. Does that help? The three secondary screws you see are the ones I had to replace since the original ones weren't long enough. When I look at how the secondary is glued to the holder, it does not look well centered as the picture shows. Regarding the tube itself being too narrow, how do I get the correct offset to get even illumination? Also, could you explain "Glued in the wrong offset"? I have understood offset to be along the tube axis, correct? Is there also offset along the perpendicular axis (i.e. the focuser axis) or should the spider just center the secondary wrt the tube?

Thanks for the detailed reply. I'm glad I wasn't the only one to have this problem.

I had recently purchased a VX8 Newtonian that was shipped to me in the USA. I was not able to get much support from OOUK on this so I am posting here with some questions. 1. Most collimating procedures I have read first want you to position the secondary to be centered in the focuser tube. When it arrived from the factory the VX8 secondary was definitely not - it was at least 10mm further out from the primary than it would have been if centered. In fact to center it in the focuser I had to put in longer adjustment screws. Is this normal? Am I missing something? 2. With the modification above, I have it centered the secondary and collimated using a Cheshire. The view through the Cheshire looks good, the crosshairs are centered on the donut mark and all three clips that hold the primary are visible. No issues with visual observation. Yet when I use a camera (ASI 294MC Pro), I see that the vignetting is quite asymmetric - i.e. much more vignetting on one side and almost none on the other. So the "sweet spot" of the FOV is not centered on the camera sensor. Any ideas of what could be causing this? The camera is mounted just as an eyepiece would be on the 2" focuser. Thanks in advance for any help/pointers.