Secondary mirror

[Adamski]

I've noticed it before and i've just done a complete collimation and it's still like it. What? you ask, well, when looking through the collimating cap i can see some of one side of the secondary mirror holder. I have centred the holder and adjusted it so that it's circular and directly below the focuser then collimated the primary mirror and it's still visible. I did notice that the secondary mirror holder is the same diameter as the mirror though, the narrow dimension of the mirror. Is this usual? The scope works fine and the images are crisp. should i worry? No matter what i do it stays the same.

[barkis]

Do a star test. Any vignetting will be obvious if it is present in the optical alignment, which will manifest in the concentric rings.

Use a high power eyepiece, and if there is no distortion of the rings, your optical alignment is fine. Any light which escapes past the secondary mirror, will become obvious in the slightly defocused star.

Ron.