Tak collimation scope

[IanL]

Hi all am trying to collimate my tak mewlon 180.
If anyone has a tak collimation scope or looked through one they will probably get what i am on about in this thread.

Takahashi collimation scope pulls in out out to get focus on collimation and what you should see is a dough nut shaped image appear in the bulls eye of it when collimated. My question is when you get the collimation point bang centre of the collimation scope. When you turn the collimation scope clock wise the point of collimation goes back out of the bulls eye that it was in. Does this show that the collimation scope could be out.

Our could this be to the tilt tip of the secondary mirror.

Thanks in advance

Ian

[garymck]

Ian,

using the Tak collimation scope you should adjust the secondary first, such that the dot on the secondary is centered in the donut, then adjust the primary so that the bright ring around the edge of the mirror is concentric. Clear as mud? Then look at this link:


http://www.dosborne-astroimages.co.uk/equip_image/collimation_article.htm

or this:

http://www.rcopticalsystems.com/support/images/rcos_alignment_collimation.pdf

It doesn't matter that they are RC's, but they are using Tak collimation scopes.

Hope this helps,
Gary

[IanL]

Yip i get what you mean but. When the secondary spot is centred in the the collimation scope. You can push and pull the collimation scope to get focus, But the push pull also rotates as well and this is when the dot goes back out of the bulls eye. I have see the links and i dont see any where that talks about rotation of the push pull on the collimations scope. All other stuff looks ok, spider, outer rings etc.

Ian