collimation

[markenroj]

how do you know if your scope needs collimating please ?

Roger.

[John]

If you put a reasonably bright star in the middle of your field of view, Polaris is good because you don't need to track it, then put in a high power eyepiece and defocuss the star so that you get a disk of light rather than a point. The disk will look a bit like a doughnut with the dark hole in the middle being the shadow of your secondary mirror. The shadow of the secondary should be central wihin the light "doughnut" - if it's offset to one side or other then your collimation is a bit off.

Hope that helps a bit.

John

[John]

For more help on this, here is a link to the Skywatcher intructions on collimation:

http://www.opticalvision.co.uk/documents/47.pdf

John

[markenroj]

cool explanation. i can see an image of the inlet of my scope when its not focused and it seems perfectly round with the centre piece in the middle thanks matey.