What's causing my spike?

I will try to explain this the best that I can. I am interested in learning what is happening here.

Note: In case it is a factor, I have some astigmatism that is being corrected in my lenses.

The other night while viewing with my glasses, I noticed that when looking at a fairly bright and focused star, if I moved my head a little, a single spike would appear coming off the star.

Wondering if this was me or the eyepiece/scope, I turned my head 90 degrees and looked again. The spike appeared again, this time in the new direction that I had turned my head, so it was following the same orientation as my eye.

What do you think is causing this?

I haven't noticed this when wearing my contacts while viewing.

Thanks,

Mark

Mark Peterman said:
What do you think is causing this?

I haven't noticed this when wearing my contacts while viewing.

I suspect your glasses have some correction for astigmatism. If so, for the best view it's important to position the eye so that the eyeglass lens is parallel to the top of the eyepiece and the exit pupil is centered where you would normally be looking straight ahead. Otherwise, your eyeglasses may add astigmatism rather than correct it. Although contact lenses may or may not correct astigmatism, depending on their type, they at least will not ADD astigmatism the way glasses do when you are not looking through the glasses in the optimal way.
--
Mike

Also, if you had a slight smear on the glasses, that can cause a spike like you are describing. Especially if it was partially cleaned by wiping with something, which will smear the grease into lots of tiny parallel lines, and act like a diffraction grate.

Jarad