collimation question//astro engineering cheshire collimator

[bottletopburly]

hi just been checking my collimation on my explorer 200p,have adjusted secondary so you just see the holders equally,and centered the primary fine all centered now heres the question the cross hairs on the collimator line through with the secondary vanes horizontally but vertically they are showing to be out a tad now can anyone tell me what i need to adjust to bring these in true ?many thanks.

[umadog]

It sounds like you've done it right (depending on what you mean by horizontal and vertical). What matters is that the cross-hairs of the collimation tool are centred on the primary mirror spot. The vanes are not a good guide for whether or not you've done it right. That said, the cross-hairs should only ever align with one site of vanes because the primary mirror spot won't be centred in the reflection of secondary (i.e. not everything should be concentric). See the image in the second post here: http://www.cloudynights.com/ubbthreads/showflat.php?Cat=0&Board=reflectors&Number=3033065

[bottletopburly]

cheers umadog seems mine is about the same as this picture http://www.cloudynights.com/ubbthreads/attachments/3033067-secondary_mirror_explained.JPG

[umadog]

Great! Then you've done it right. Make sure you pay the most attention to the primary tilt adjustment, as this is the most critical one. Once you're happy it's all good you should start-test it (defocusing just enough to see the first few diffraction rings. Google if unsure). If the star test looks good then you're procedures are good and you won't need to star test every time (unless you want to, or suspect that the collimation is drifting during the night). Your scope is f/5 so it'll be relatively sensitive to being misaligned.

[bottletopburly]

thanks umadog for your advice