Edge noise to CCD images and aligning a secondary mirror

[Dennis G]

Occasionally I've produced the odd picture with a narrow (5 mm) band of noise - my description - along the top and usually down left hand side and although it can be removed by cropping the picture it leaves one wondering why. I've experienced this problem or fault when recording with the Toucam in both my 200mm and the new 250mm and as above, it doesn't appear in all the pictures (CCD images) A little back ground info may assist a member to provide a clue.
The 200mm Dob I made entirely from scratch following Berry's book and it proved to be an excellent scope.
When I received the 250mm GSO the secondary mirror was out of alignment and took a lot of fiddling to get it realigned. I spotted the secondary mirror as per Berry's instructions and diagram that covers numerous secondary mirror sizes and made a 150 mm long sight tube with a 2mm sight hole and cross hairs and using this I eventually managed to get the reflected circular image of both mirrors lined up to the tube and collimated as close as I'm able to do so.
Questions:
Is there any better way of aligning a secondary mirror?
Could the edge noise be caused by the processing in Registax?

[vash]

the edge noise I believe would be coming from processing, if there is movement in your frames the outside edge will not have the same amount of stacked frames as the center, I get this in most of my Images, you can put a small boarder around the image or crop it, if your tracking was perfect you would most likely not even notice it.
I'm not sure about the secondary if it would effect anything.