From: "Jan van Gastel" 
To: 
Reply-To: "Jan van Gastel" 


Even more important is, that the laser beam hits the exact optical center
of the primary. If not, the primary mirror optical axis will not point at
the center of the focal plnae when the laser reflects back on itsself.

Jan
http://home.wanadoo.nl/jhm.vangastel/

----- Original Message -----
From: "Dennis Rech" 
To: "Rick Maillet" ; 
Sent: Monday, April 14, 2003 5:58 AM Subject: Re: ATM Collimation question


>
> At 07:31 AM 4/13/03 -0700, Rick Maillet wrote:
> >When the laser light is centered on the primary, and
> >reflects back to the point of origion, (this I assume
> >is when the optics are in alignment) If I then place a
> >piece of paper in front of the tube opening, there is
> >a red circle showing, around the secondary on the
> >paper,this circle appears even all the way around.
> >
> >I am thinking this means my secondary is to close to
> >the primary and not catching all the rays returning
> >from the primary, does this make sense.
> >I assume no light should get past the secondary, is
> >this correct.
> >
> >                                                    Rick
>
> Hi Rick,
> Make sure that the laser pointer beam FIRST hits the center of the
diagonal.
> And after it reflects off the mirror that it again hits the center of the
> diagonal.
>
> It is entirely possible to have a reflection back to the point of origin
> and be way out of collimation.
>
> Its best to put a small 1/2" diameter paper hole reinforcement ring on the
> center of the diagonal and another on the center of the mirror before
doing
> the laser pointer alignment trick.
>
> Its not uncommon to have the  diagonal off centered and axially
> displaced  by an inch or so and still get the reflection to return to the
> starting point.
>
> I have come across people who think that they have made horrible mirrors
> that only have misplaced diagonals.
> I like to cut a foot long piece of 1.25 inch diameter dowel with a 45
> degree wedge on one end and put it into the eyepiece and run it all the
way
> to the diagonal. It will quickly show it the diagonal is misplaced and if
> the eyepiece holder is canted.
>
> Hope this helps,
> Dennis
>
>
>
>

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