star test

Question about a star test. When I do a star test, I notice that the
black circle in the middle is between the spider veins, but the spider
veins and the circle are slightly off center. The circle is fully
formed.

If the circle and the spider vanes are slightly off center, what does
this indicate?

Also, I notice that there are holes in the outside area next to the
spider veins. Does this indicate debris?



Input appreciated.
Bruce

On Mar 22, 8:38 am, "brucegooglegroups"
wrote:
Question about a star test. When I do a star test, I notice that the
black circle in the middle is between the spider veins, but the spider
veins and the circle are slightly off center. The circle is fully
formed.

If the circle and the spider vanes are slightly off center, what does
this indicate?

Also, I notice that there are holes in the outside area next to the
spider veins. Does this indicate debris?

Input appreciated.
Bruce

The black circle is the shadow of the secondary. What it means depends
on the telescope. It may mean miscollimation. Or it may be the normal
secondary offset of a fast newtonian.

Unk Rod

brucegooglegroups wrote:

Question about a star test. When I do a star test, I notice that the
black circle in the middle is between the spider veins, but the spider
veins and the circle are slightly off center. The circle is fully
formed.

If the circle and the spider vanes are slightly off center, what does
this indicate?

It indicates the scope is not collimated. Adjust the primary to bring
the spider veins and centered dark circle bacn on dead center.
A black dot in the middle of your primary will help.




Also, I notice that there are holes in the outside area next to the
spider veins. Does this indicate debris?

Holes? Holes being seen on the tube walls near where the spider
veins attach? Debris? Debris from what (having drilled the tube
to attach the spider and finder and whatever else?).

Find a collimation website on the net. There are dozens. Pick the
one youfind the simplest to follow and follow it, step by step. All
will become clear. You need to spend time learning what parts of
the telescope you are seeing as you look through the eyepiece tube. Its
very confusing at first. Once that becomes clear then the
collimation procedure will be easier. Find a good website!
Good luck -





Input appreciated.
Bruce

On Mar 23, 3:00 am, KLM wrote:
brucegooglegroups wrote:


If the circle and the spider vanes are slightly off center, what does
this indicate?

It indicates the scope is not collimated. Adjust the primary to bring
the spider veins and centered dark circle bacn on dead center.
A black dot in the middle of your primary will help.


I adjusted the primary to bring the bring the dot into the middle.

Also, I notice that there are holes in the outside area next to the
spider veins. Does this indicate debris?

Holes? Holes being seen on the tube walls near where the spider
veins attach? Debris? Debris from what (having drilled the tube
to attach the spider and finder and whatever else?).

The debris consists of a lot of dust and a hair.

The main question now is how do I tell if the secondary is collimated?
Thanks.
Bruce

brucegooglegroups wrote:
On Mar 23, 3:00 am, KLM wrote:
brucegooglegroups wrote:

If the circle and the spider vanes are slightly off center, what does
this indicate?
It indicates the scope is not collimated. Adjust the primary to bring
the spider veins and centered dark circle bacn on dead center.
A black dot in the middle of your primary will help.


I adjusted the primary to bring the bring the dot into the middle.

Also, I notice that there are holes in the outside area next to the
spider veins. Does this indicate debris?
Holes? Holes being seen on the tube walls near where the spider
veins attach? Debris? Debris from what (having drilled the tube
to attach the spider and finder and whatever else?).

The debris consists of a lot of dust and a hair.

The main question now is how do I tell if the secondary is collimated?
Thanks.
Bruce



Just a comment, If you are racking in so far that you are seeing the
secondary and spider then you are going much too far to consider this
any kind of "star test". Drill a hole in the center of a 35 mm film can
for use as an "eyepiece" and in the daylight center everything up so
that when you look in the eyepiece the diagonal is centered in the
eyepiece and on the primary. Final collimation by star test is looking
at the Airy pattern for coencetricity.

--
jeff