Installed a JMI Focuser on my 10" Meade Starfinder. I put a reinforcement ring in the exact center of the primary.Collimated the diagonal and then started the primary.Problem is I cannot get the "ring" in the center of the diagonal. I run out of screw adjustment. What is this telling me? The diagonal is not lined up? Any help appreciated since I am new to this.
Trouble lining up Primary Mirror
Started by astroham2003, 10/10/2004 07:07PM
Posted 10/10/2004 07:07PM
Opening Post
Posted 10/10/2004 07:27PM
#1
John,
I cannot quite tell what your problem is.
Are you using a laser to do this?
Starting back at the part of your post when you said, "Collimated the diagonal." What do you mean by this? Collimating the diagonal is the procedure that puts the center dot in the center of the secondary. The reasons this may not work is that the primary mirror cell itself is off center. (or the mirror is off center in the cell.)
When are you running out of screw travel? Theoretically, you can never run out of screw travel because, if you do, you just back the other two screws the other way.
And, by the way, you should collimate, whenever possible, with your screws as short at they reasonably can be (the back of the mirror is closer to the mirror cell). (This is not that big a deal with smaller mirrors, and you must consider the focuser travel when doing this.)
Write back with more details.
Alex
I cannot quite tell what your problem is.
Are you using a laser to do this?
Starting back at the part of your post when you said, "Collimated the diagonal." What do you mean by this? Collimating the diagonal is the procedure that puts the center dot in the center of the secondary. The reasons this may not work is that the primary mirror cell itself is off center. (or the mirror is off center in the cell.)
When are you running out of screw travel? Theoretically, you can never run out of screw travel because, if you do, you just back the other two screws the other way.
And, by the way, you should collimate, whenever possible, with your screws as short at they reasonably can be (the back of the mirror is closer to the mirror cell). (This is not that big a deal with smaller mirrors, and you must consider the focuser travel when doing this.)
Write back with more details.
Alex
Posted 10/10/2004 08:06PM
#2
First off, the replacement of the focuser will not change the mirror collimation.
The only thing that this can do is change the angle of the focuser to the secondary. This should not change as long as the original focuser was mounted flat to the focuser board. If it was angled then the new focuser should be adjusted to be perpendicular with the secondary before any other adjustments are made.
I suggest that you need to use a sight tube or Cheshire to set the relationship between the focuser and the secondary mirror. Then you would adjust the secondary to the primary. Followed by the primary back to the secondary. This is easily done with a laser and can be done with the Cheshire.
Floyd
The only thing that this can do is change the angle of the focuser to the secondary. This should not change as long as the original focuser was mounted flat to the focuser board. If it was angled then the new focuser should be adjusted to be perpendicular with the secondary before any other adjustments are made.
I suggest that you need to use a sight tube or Cheshire to set the relationship between the focuser and the secondary mirror. Then you would adjust the secondary to the primary. Followed by the primary back to the secondary. This is easily done with a laser and can be done with the Cheshire.
Floyd
[SIZE="Large"][/SIZE][COLOR="Blue"][/COLOR] Floyd Blue
Amateur Imager
Posted 10/10/2004 11:36PM
#3
On traditional 3 point primary adjusters, to move the mirror in a specific way, you can either move one screw one way, or the other 2 screws in the oppostie direction.
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