scratch on primary mirror

Will a small light scratch on the primary mirror have any effect on it's performance? I underwent the task of trying to remove the donut from the center of the mirror, so I could apply the reflective triangle for the "catseye" collimation tool. Following the instructions, I used acetone in an attempt to loosen the adhesive of the donut, but was unsuccessful at removing it, so just blackened it with a marker,and applied the triangle on top of it. Anyway, in the process of screwing around with the mirror, I created some smudges, so cleaned it, afterwards noticed a small, light scratch. Will that effect the mirror's performance? Thanks.

No, a small scratch will not effect the mirror's performance. Even a few small scratches would not be an issue.

Possibly (probably) it will scatter some light; but the amount of scatter should be negligble, I.E. you won't notice it (your eyepieces probably scatter more light than would be introduced by a scratch). Also, examine the scratch with a magnifying lens ( a low-power eyepiece with barrel removed would do, as long as lens set remains in housing), it may just be a sleek in the coating rather than a scratch in the glass itself; in this case more sleeks may occur due to frequent/inappropriate cleaning method(s) and when you eventually re-aluminize the mirror the *scratch* will be gone. Also, if this scratch is primarily in the central area *hidden* by the secondary shadow (as is your index mark) then it is of no consequence. Ron

The secondary mirror is more sensitive to scratches, but I have used them with a lot of small scratches and sleeks without it being a real problem. Certainly it will cause more light scatter because the light is concentrated from the larger mirror, but it is not the end of the world. Just try to keep it from becoming too scratched or even too dirty..
Floyd