collimation of secondary mirror

When I place a piece of white paper on the opposite side of the tube
from the secondary mirror, I see only the secondary mirror.

What am I looking for to check the collimation of the secondary?

Looking down the focuser tube I do see the secondary mirror- which
looks more or less centered in the focuser-should I look for anything
else?
Bruce

On Jun 8, 2:55*pm, brucegooglegroups
wrote:
When I place a piece of white paper on the opposite side of the tube
from the secondary mirror, I see only the secondary mirror.

What am I looking for to check the collimation of the secondary?

Looking down the focuser tube I do see the secondary mirror- *which
looks more or less centered in the focuser-should I look for anything
else?
Bruce


You should be looking for two things:
1. That the reflecting part of the secondary mirror is centered with
the optical axis of the eyepiece.
2. That the reflection of the objective mirror, is centered in the
diagonal mirror.

To be really precise about this, you should be using an alignment aid,
such as a piece of plastic which fits into the focuser, with a small
hole drilled in the center, or a collimating eyepiece such as Orion's:

http://www.telescope.com/control/pro...oduct_id=03640

AND, the top sighting hole should be positioned very closely to the
prime focus of the telescope, which is usually about 1/2 inch above
the top of the focuser draw tube when racked all the way in.

google collimation.



brucegooglegroups wrote:

When I place a piece of white paper on the opposite side of the tube
from the secondary mirror, I see only the secondary mirror.

What am I looking for to check the collimation of the secondary?

Looking down the focuser tube I do see the secondary mirror- which
looks more or less centered in the focuser-should I look for anything
else?
Bruce