CA with ED100

[West End Wendy]

Recently I've noticed some definite colour on bright objects with my Skywatcher ED100, specifically a red fringe on one side of the object and blue on the other.

I assume this is CA, but I don't remember seeing it before (owned the scope 3 months).

My best guess is that poor seeing is responsible, as I don't expect my scope to be colour-free when out of focus, and poor seeing makes consistent good focus difficult. Or maybe I need to leave the scope longer to cool.

Are these reasonable explanations?

Tim

[jgs001]

Tim, I think it's the atmospherics... I've seen this on occasion bright targets, like Jupiter, low in the sky. I've never noticed this sort of effect otherwise.

[Peter Drew]

Definitely atmospheric refraction, this will produce the same effect on reflectors which do not have CA. Genuine CA will surround the object in view and will generally be one colour, usually violet.

[perrin6]

Dirty optics ??

[West End Wendy]

Thanks that makes sense.

It was particularly noticeable on Jupiter, and also Sirius (but then Sirius often looks multi-coloured to me with the naked eye…)